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  -*-LaTeX-*-


hacked for caml - all except a few lines are commented out with a % in column 0


                                   Part: IV
                                   ********
                          The Objective Caml library
                          **************************
    
  

Chapter 19    The core library
******************************
%    
%  This chapter describes the Objective Caml core library, which is  composed of
%declarations for built-in types and exceptions, plus the module Pervasives that
%provides basic operations on these  built-in types. The Pervasives module is
%special in two ways: 
%  
% - It is automatically linked with the user-s object code files by the ocamlc
%   command (chapter 8).
% 
% - It is automatically --opened-- when a compilation starts, or when the
%   toplevel system is launched. Hence, it is possible to use unqualified
%   identifiers to refer to the functions provided by the Pervasives module,
%   without adding a open Pervasives directive. 
%  
%
%Conventions
%*=*=*=*=*=*
%
%  
%  The declarations of the built-in types and the components of module
%Pervasives are printed one by one in typewriter font, followed by a short
%comment. All library modules and the components they provide are indexed at the
%end of this report.
%  
%
%19.1  Built-in types and predefined exceptions
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%  
%  The following built-in types and predefined exceptions are always defined in
%the compilation environment, but are not part of any module. As a consequence,
%they can only be referred by their short names.
%
Built-in types
==============
%   
%<<
   type int
%>>
%    
%                 The type of integer numbers. 
%  
%<<
   type char
%>>
%    
%                 The type of characters. 
%  
%<<
   type string
%>>
%    
%                 The type of character strings. 
%  
%<<
   type float
%>>
%    
%                 The type of floating-point numbers. 
%  
%<<
   type bool = false | true
%>>
%    
%                 The type of booleans (truth values). 
%  
%<<
   type unit = ()
%>>
%    
%                 The type of the unit value. 
%  
%<<
   type exn
%>>
%    
%                 The type of exception values. 
%  
%<<
%   type 'a array
%>>
%    
%                 The type of arrays whose elements have type 'a. 
%  
%<<
   type 'a list = [] | :: of 'a * 'a list
%>>
%    
%                 The type of lists whose elements have type 'a. 
%  
%<<
   type 'a option = None | Some of 'a
%>>
%    
%                 The type of optional values of type 'a.  
%  
%<<
%  type int32
%>>
%    
%                 The type of signed 32'bit integers.   See the Int32[Int32]
%               module. 
%  
%<<
%  type int64
%>>
%    
%                 The type of signed 64'bit integers.   See the Int64[Int64]
%               module. 
%  
%<<
%  type nativeint
%>>
%    
%                 The type of signed, platform-native integers (32 bits on
%               32'bit  processors, 64 bits on 64'bit processors).  See the
%               Nativeint[Nativeint] module. 
%  
%<<
%  type ('a, 'b, 'c, 'd) format4
%>>
%    
%                 The type of format strings. 'a is the type of the parameters 
%               of the format, 'd is the result type for the printf-style 
%               function, 'b is the type of the first argument given to  \%a and
%               \%t printing functions (see module Printf[Printf]),  and 'c is
%               the result type of these functions. 
%  
%<<
%  type 'a lazy_t
%>>
%    
%                 This type is used to implement the Lazy[Lazy] module.  It
%               should not be used directly. 
%  
%
Predefined exceptions
=====================
%   
%<<
  exception Match_failure of (string * int * int)
%>>
%    
%                 Exception raised when none of the cases of a pattern-matching 
%               apply. The arguments are the location of the match keyword  in
%               the source code (file name, line number, column number). 
%  
%<<
  exception Assert_failure of (string * int * int)
%>>
%    
%                 Exception raised when an assertion fails. The arguments are 
%               the location of the assert keyword in the source code  (file
%               name, line number, column number). 
%  
%<<
  exception Invalid_argument of string
%>>
%    
%                 Exception raised by library functions to signal that the given
%                arguments do not make sense. 
%  
%<<
  exception Failure of string
%>>
%    
%                 Exception raised by library functions to signal that they are 
%               undefined on the given arguments.  
%  
%<<
  exception Not_found
%>>
%    
%                 Exception raised by search functions when the desired object 
%               could not be found. 
%  
%<<
%  exception Out_of_memory
%>>
%    
%                 Exception raised by the garbage collector  when there is
%               insufficient memory to complete the computation. 
%  
%<<
%  exception Stack_overflow
%>>
%    
%                 Exception raised by the bytecode interpreter when the
%               evaluation  stack reaches its maximal size. This often indicates
%               infinite  or excessively deep recursion in the user-s program. 
%               (Not fully implemented by the native'code compiler;  see section
%               11.5.) 
%  
%<<
%  exception Sys_error of string
%>>
%    
%                 Exception raised by the input/output functions to report  an
%               operating system error. 
%  
%<<
%  exception End_of_file
%>>
%    
%                 Exception raised by input functions to signal that the  end of
%               file has been reached. 
%  
%<<
  exception Division_by_zero
%>>
%    
%                 Exception raised by division and remainder operations  when
%               their second argument is null.  (Not fully implemented by the
%               native'code compiler;  see section 11.5.) 
%  
%<<
%  exception Sys_blocked_io
%>>
%    
%                 A special case of Sys_error raised when no I/O is possible  on
%               a non'blocking I/O channel. 
%  
%<<
%  exception Undefined_recursive_module of (string * int * int)
%>>
%    
%                 Exception raised when an ill-founded recursive module
%               definition  is evaluated. (See section 7.9.)  The arguments are
%               the location of the definition in the source code  (file name,
%               line number, column number). 
%  
%  
%

19.2  Module Pervasives : The initially opened module.
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module provides the basic operations over the built-in types  (numbers,
%booleans, strings, exceptions, references, lists, arrays,  input-output
%channels, ...)
%  This module is automatically opened at the beginning of each compilation. 
%All components of this module can therefore be referred by their short  name,
%without prefixing them by Pervasives.
%  0.5cm
%
Exceptions
==========
%  
%<<
  val raise : exn -> 'a
%>>
%    
%                Raise the given exception value
%  
%<<
%  val invalid_arg : string -> 'a
%>>
%    
%                Raise exception Invalid_argument with the given string.
%  
%<<
%  val failwith : string -> 'a
%>>
%    
%                Raise exception Failure with the given string.
%  
%<<
%  exception Exit
%>>
%    
%                The Exit exception is not raised by any library function. It is
%                provided for use in your programs.
%  
%
Comparisons
===========

** do we need to make these less polymorphic? **

%  
%<<
  val (=) : 'a -> 'a -> bool
%>>
%    
%                e1 = e2 tests for structural equality of e1 and e2.  Mutable
%               structures (e.g. references and arrays) are equal  if and only
%               if their current contents are structurally equal,  even if the
%               two mutable objects are not the same physical object.  Equality
%               between functional values raises Invalid_argument.  Equality
%               between cyclic data structures does not terminate.
%  
%<<
  val (<>) : 'a -> 'a -> bool
%>>
%    
%                Negation of Pervasives.(=)[19.2].
%  
%<<
  val (<) : 'a -> 'a -> bool
%>>
%    
%                See Pervasives.(>=)[19.2].
%  
%<<
  val (>) : 'a -> 'a -> bool
%>>
%    
%                See Pervasives.(>=)[19.2].
%  
%<<
  val (<=) : 'a -> 'a -> bool
%>>
%    
%                See Pervasives.(>=)[19.2].
%  
%<<
  val (>=) : 'a -> 'a -> bool
%>>
%    
%                Structural ordering functions. These functions coincide with 
%               the usual orderings over integers, characters, strings  and
%               floating-point numbers, and extend them to a  total ordering
%               over all types.  The ordering is compatible with (=). As in the
%               case  of (=), mutable structures are compared by contents. 
%               Comparison between functional values raises Invalid_argument. 
%               Comparison between cyclic structures does not terminate.
%  
%<<
  val compare : 'a -> 'a -> int
%>>
%    
%                compare x y returns 0 if x is equal to y,  a negative integer
%               if x is less than y, and a positive integer  if x is greater
%               than y. The ordering implemented by compare  is compatible with
%               the comparison predicates =, < and >  defined above, with one
%               difference on the treatment of the float value 
%               Pervasives.nan[19.2]. Namely, the comparison predicates treat
%               nan  as different from any other float value, including itself; 
%               while compare treats nan as equal to itself and less than any 
%               other float value. This treatment of nan ensures that compare 
%               defines a total ordering relation.
%               compare applied to functional values may raise Invalid_argument.
%                compare applied to cyclic structures may not terminate.
%               The compare function can be used as the comparison function 
%               required by the Set.Make[20.28] and Map.Make[20.18] functors, as
%               well as  the List.sort[20.17] and Array.sort[20.2] functions.
%  
%<<
%  val min : 'a -> 'a -> 'a
%>>
%    
%                Return the smaller of the two arguments.
%  
%<<
%  val max : 'a -> 'a -> 'a
%>>
%    
%                Return the greater of the two arguments.
%  
%<<
%  val (==) : 'a -> 'a -> bool
%>>
%    
%                e1 == e2 tests for physical equality of e1 and e2.  On integers
%               and characters, physical equality is identical to structural 
%               equality. On mutable structures, e1 == e2 is true if and only if
%                physical modification of e1 also affects e2.  On non-mutable
%               structures, the behavior of (==) is  implementation-dependent;
%               however, it is guaranteed that  e1 == e2 implies compare e1 e2 =
%               0.
%  
%<<
%  val (!=) : 'a -> 'a -> bool
%>>
%    
%                Negation of Pervasives.(==)[19.2].
%  
%
Boolean operations
==================
%  
%<<
  val not : bool -> bool
%>>
%    
%                The boolean negation.
%  
%<<
  val (&&) : bool -> bool -> bool
%>>
%    
%                The boolean -'and--. Evaluation is sequential, left-to-right: 
%               in e1 && e2, e1 is evaluated first, and if it returns false,  e2
%               is not evaluated at all.
%  
%<<
%  val (&) : bool -> bool -> bool
%>>
%    
%                Deprecated. Pervasives.(&&)[19.2] should be used instead. 
%  
%<<
  val (||) : bool -> bool -> bool
%>>
%    
%                The boolean --or--. Evaluation is sequential, left-to-right: 
%               in e1 || e2, e1 is evaluated first, and if it returns true,  e2
%               is not evaluated at all.
%  
%<<
%  val or : bool -> bool -> bool
%>>
%    
%                Deprecated. Pervasives.(||)[19.2] should be used instead. 
%  
%
Integer arithmetic
==================
  
  Integers are 31 bits wide (or 63 bits on 64'bit processors).  All operations
are taken modulo 2^31 (or 2^63).  They do not fail on overflow.
%<<
%  val (~-) : int -> int
%>>
%    
%                Unary negation. You can also write -e instead of ~-e.
%  
%<<
%  val succ : int -> int
%>>
%    
%                succ x is x+1.
%  
%<<
%  val pred : int -> int
%>>
%    
%                pred x is x-1.
%  
%<<
  val (+) : int -> int -> int
%>>
%    
%                Integer addition.
%  
%<<
  val (-) : int -> int -> int
%>>
%    
%                Integer subtraction.
%  
%<<
  val (*) : int -> int -> int
%>>
%    
%                Integer multiplication.
%  
%<<
  val (/) : int -> int -> int
%>>
%    
%                Integer division.  Raise Division_by_zero if the second
%               argument is 0.  Integer division rounds the real quotient of its
%               arguments towards zero.  More precisely, if x >= 0 and y > 0, x
%               / y is the greatest integer  less than or equal to the real
%               quotient of x by y. Moreover,  (-x) / y = x / (-y) = -(x / y).
%  
%<<
%  val mod : int -> int -> int
%>>
%    
%                Integer remainder. If y is not zero, the result  of x mod y
%               satisfies the following properties:  x = (x / y) * y + x mod y
%               and  abs(x mod y) <= abs(y)-1.  If y = 0, x mod y raises
%               Division_by_zero.  Notice that x mod y is negative if and only
%               if x < 0.
%  
%<<
%  val abs : int -> int
%>>
%    
%                Return the absolute value of the argument.
%  
%<<
  val max_int : int
%>>
%    
%                The greatest representable integer.
%  
%<<
  val min_int : int
%>>
%    
%                The smallest representable integer.
%  
%
%Bitwise operations
%------------------
%  
%<<
%  val land : int -> int -> int
%>>
%    
%                Bitwise logical and.
%  
%<<
%  val lor : int -> int -> int
%>>
%    
%                Bitwise logical or.
%  
%<<
%  val lxor : int -> int -> int
%>>
%    
%                Bitwise logical exclusive or.
%  
%<<
%  val lnot : int -> int
%>>
%    
%                Bitwise logical negation.
%  
%<<
%  val lsl : int -> int -> int
%>>
%    
%                n lsl m shifts n to the left by m bits.  The result is
%               unspecified if m < 0 or m >= bitsize,  where bitsize is 32 on a
%               32'bit platform and  64 on a 64'bit platform.
%  
%<<
%  val lsr : int -> int -> int
%>>
%    
%                n lsr m shifts n to the right by m bits.  This is a logical
%               shift: zeroes are inserted regardless of  the sign of n.  The
%               result is unspecified if m < 0 or m >= bitsize.
%  
%<<
%  val asr : int -> int -> int
%>>
%    
%                n asr m shifts n to the right by m bits.  This is an arithmetic
%               shift: the sign bit of n is replicated.  The result is
%               unspecified if m < 0 or m >= bitsize.
%  
%
%Floating-point arithmetic
%=========================
%  
%  Caml-s floating-point numbers follow the  IEEE 754 standard, using double
%precision (64 bits) numbers.  Floating-point operations never raise an
%exception on overflow,  underflow, division by zero, etc. Instead, special IEEE
%numbers  are returned as appropriate, such as infinity for 1.0 /. 0.0, 
%neg_infinity for -1.0 /. 0.0, and nan (--not a number--)  for 0.0 /. 0.0. These
%special numbers then propagate through  floating-point computations as
%expected: for instance,  1.0 /. infinity is 0.0, and any operation with nan as 
% argument returns nan as result.
%<<
%  val (~-.) : float -> float
%>>
%    
%                Unary negation. You can also write -.e instead of ~-.e.
%  
%<<
%  val (+.) : float -> float -> float
%>>
%    
%                Floating-point addition
%  
%<<
%  val (-.) : float -> float -> float
%>>
%    
%                Floating-point subtraction
%  
%<<
%  val (*.) : float -> float -> float
%>>
%    
%                Floating-point multiplication
%  
%<<
%  val (/.) : float -> float -> float
%>>
%    
%                Floating-point division.
%  
%<<
%  val (**) : float -> float -> float
%>>
%    
%                Exponentiation
%  
%<<
%  val sqrt : float -> float
%>>
%    
%                Square root
%  
%<<
%  val exp : float -> float
%>>
%    
%                Exponential.
%  
%<<
%  val log : float -> float
%>>
%    
%                Natural logarithm.
%  
%<<
%  val log10 : float -> float
%>>
%    
%                Base 10 logarithm.
%  
%<<
%  val cos : float -> float
%>>
%    
%                See Pervasives.atan2[19.2].
%  
%<<
%  val sin : float -> float
%>>
%    
%                See Pervasives.atan2[19.2].
%  
%<<
%  val tan : float -> float
%>>
%    
%                See Pervasives.atan2[19.2].
%  
%<<
%  val acos : float -> float
%>>
%    
%                See Pervasives.atan2[19.2].
%  
%<<
%  val asin : float -> float
%>>
%    
%                See Pervasives.atan2[19.2].
%  
%<<
%  val atan : float -> float
%>>
%    
%                See Pervasives.atan2[19.2].
%  
%<<
%  val atan2 : float -> float -> float
%>>
%    
%                The usual trigonometric functions.
%  
%<<
%  val cosh : float -> float
%>>
%    
%                See Pervasives.tanh[19.2].
%  
%<<
%  val sinh : float -> float
%>>
%    
%                See Pervasives.tanh[19.2].
%  
%<<
%  val tanh : float -> float
%>>
%    
%                The usual hyperbolic trigonometric functions.
%  
%<<
%  val ceil : float -> float
%>>
%    
%                See Pervasives.floor[19.2].
%  
%<<
%  val floor : float -> float
%>>
%    
%                Round the given float to an integer value.  floor f returns the
%               greatest integer value less than or  equal to f.  ceil f returns
%               the least integer value greater than or  equal to f.
%  
%<<
%  val abs_float : float -> float
%>>
%    
%                Return the absolute value of the argument.
%  
%<<
%  val mod_float : float -> float -> float
%>>
%    
%                mod_float a b returns the remainder of a with respect to  b.
%               The returned value is a -. n *. b, where n  is the quotient a /.
%               b rounded towards zero to an integer.
%  
%<<
%  val frexp : float -> float * int
%>>
%    
%                frexp f returns the pair of the significant  and the exponent
%               of f. When f is zero, the  significant x and the exponent n of f
%               are equal to  zero. When f is non-zero, they are defined by  f =
%               x *. 2 ** n and 0.5 <= x < 1.0.
%  
%<<
%  val ldexp : float -> int -> float
%>>
%    
%                ldexp x n returns x *. 2 ** n.
%  
%<<
%  val modf : float -> float * float
%>>
%    
%                modf f returns the pair of the fractional and integral  part of
%               f.
%  
%<<
%  val float : int -> float
%>>
%    
%                Same as Pervasives.float_of_int[19.2].
%  
%<<
%  val float_of_int : int -> float
%>>
%    
%                Convert an integer to floating-point.
%  
%<<
%  val truncate : float -> int
%>>
%    
%                Same as Pervasives.int_of_float[19.2].
%  
%<<
%  val int_of_float : float -> int
%>>
%    
%                Truncate the given floating-point number to an integer.  The
%               result is unspecified if it falls outside the  range of
%               representable integers.
%  
%<<
%  val infinity : float
%>>
%    
%                Positive infinity.
%  
%<<
%  val neg_infinity : float
%>>
%    
%                Negative infinity.
%  
%<<
%  val nan : float
%>>
%    
%                A special floating-point value denoting the result of an 
%               undefined operation such as 0.0 /. 0.0. Stands for  --not a
%               number--. Any floating-point operation with nan as  argument
%               returns nan as result. As for floating-point comparisons,  =, <,
%               <=, > and >= return false and <> returns true  if one or both of
%               their arguments is nan.
%  
%<<
%  val max_float : float
%>>
%    
%                The largest positive finite value of type float.
%  
%<<
%  val min_float : float
%>>
%    
%                The smallest positive, non-zero, non-denormalized value of type
%               float.
%  
%<<
%  val epsilon_float : float
%>>
%    
%                The smallest positive float x such that 1.0 +. x <> 1.0.
%  
%<<
%  type fpclass =
%    | FP_normal
%>>
%   
%                Normal number, none of the below 
%   
%<<
%    | FP_subnormal
%>>
%   
%                Number very close to 0.0, has reduced precision 
%   
%<<
%    | FP_zero
%>>
%   
%                Number is 0.0 or -0.0 
%   
%<<
%    | FP_infinite
%>>
%   
%                Number is positive or negative infinity 
%   
%<<
%    | FP_nan
%>>
%   
%                Not a number: result of an undefined operation 
%    
%                The five classes of floating-point numbers, as determined by 
%               the Pervasives.classify_float[19.2] function.
%  
%<<
%  val classify_float : float -> fpclass
%>>
%    
%                Return the class of the given floating-point number:  normal,
%               subnormal, zero, infinite, or not a number.
%  
%
String operations
=================
%  
%  More string operations are provided in module String[20.33].
%<<
  val (^) : string -> string -> string
%>>
%    
%                String concatenation.
%  
%
%Character operations
%====================
%  
%  More character operations are provided in module Char[20.5].
%<<
%  val int_of_char : char -> int
%>>
%    
%                Return the ASCII code of the argument.
%  
%<<
%  val char_of_int : int -> char
%>>
%    
%                Return the character with the given ASCII code.  Raise
%               Invalid_argument "char_of_int" if the argument is  outside the
%               range 0--255.
%  
%
Unit operations
===============
%  
%<<
  val ignore : 'a -> unit
%>>
%    
%                Discard the value of its argument and return ().  For instance,
%               ignore(f x) discards the result of  the side-effecting function
%               f. It is equivalent to  f x; (), except that the latter may
%               generate a  compiler warning; writing ignore(f x) instead 
%               avoids the warning.
%  
%
%String conversion functions
%===========================
%  
%<<
%  val string_of_bool : bool -> string
%>>
%    
%                Return the string representation of a boolean.
%  
%<<
%  val bool_of_string : string -> bool
%>>
%    
%                Convert the given string to a boolean.  Raise Invalid_argument
%               "bool_of_string" if the string is not  "true" or "false".
%  
%<<
%  val string_of_int : int -> string
%>>
%    
%                Return the string representation of an integer, in decimal.
%  
%<<
%  val int_of_string : string -> int
%>>
%    
%                Convert the given string to an integer.  The string is read in
%               decimal (by default) or in hexadecimal (if it  begins with 0x or
%               0X), octal (if it begins with 0o or 0O),  or binary (if it
%               begins with 0b or 0B).  Raise Failure "int_of_string" if the
%               given string is not  a valid representation of an integer, or if
%               the integer represented  exceeds the range of integers
%               representable in type int.
%  
%<<
%  val string_of_float : float -> string
%>>
%    
%                Return the string representation of a floating-point number.
%  
%<<
%  val float_of_string : string -> float
%>>
%    
%                Convert the given string to a float. Raise Failure
%               "float_of_string"  if the given string is not a valid
%               representation of a float.
%  
%
%Pair operations
%===============
%  
%<<
%  val fst : 'a * 'b -> 'a
%>>
%    
%                Return the first component of a pair.
%  
%<<
%  val snd : 'a * 'b -> 'b
%>>
%    
%                Return the second component of a pair.
%  
%
List operations
===============
%  
%  More list operations are provided in module List[20.17].
%<<
  val (@) : 'a list -> 'a list -> 'a list
%>>
%    
%                List concatenation.
%  
%
Input/output
============
%  
%<<
%  type in_channel 
%>>
%    
%                The type of input channel.
%  
%<<
%  type out_channel 
%>>
%    
%                The type of output channel.
%  
%<<
%  val stdin : in_channel
%>>
%    
%                The standard input for the process.
%  
%<<
%  val stdout : out_channel
%>>
%    
%                The standard output for the process.
%  
%<<
%  val stderr : out_channel
%>>
%    
%                The standard error ouput for the process.
%  
%
%Output functions on standard output
%-----------------------------------
%  
%<<
%  val print_char : char -> unit
%>>
%    
%                Print a character on standard output.
%  
%<<
  val print_string : string -> unit
%>>
%    
%                Print a string on standard output.
%  
%<<
%  val print_int : int -> unit
%>>
%    
%                Print an integer, in decimal, on standard output.
%  
%<<
%  val print_float : float -> unit
%>>
%    
%                Print a floating-point number, in decimal, on standard output.
%  
%<<
%  val print_endline : string -> unit
%>>
%    
%                Print a string, followed by a newline character, on  standard
%               output and flush standard output.
%  
%<<
%  val print_newline : unit -> unit
%>>
%    
%                Print a newline character on standard output, and flush 
%               standard output. This can be used to simulate line  buffering of
%               standard output.
%  
%
%Output functions on standard error
%----------------------------------
%  
%<<
%  val prerr_char : char -> unit
%>>
%    
%                Print a character on standard error.
%  
%<<
%  val prerr_string : string -> unit
%>>
%    
%                Print a string on standard error.
%  
%<<
%  val prerr_int : int -> unit
%>>
%    
%                Print an integer, in decimal, on standard error.
%  
%<<
%  val prerr_float : float -> unit
%>>
%    
%                Print a floating-point number, in decimal, on standard error.
%  
%<<
%  val prerr_endline : string -> unit
%>>
%    
%                Print a string, followed by a newline character on standard
%               error  and flush standard error.
%  
%<<
%  val prerr_newline : unit -> unit
%>>
%    
%                Print a newline character on standard error, and flush 
%               standard error.
%  
%
%Input functions on standard input
%---------------------------------
%  
%<<
%  val read_line : unit -> string
%>>
%    
%                Flush standard output, then read characters from standard input
%                until a newline character is encountered. Return the string of 
%               all characters read, without the newline character at the end.
%  
%<<
%  val read_int : unit -> int
%>>
%    
%                Flush standard output, then read one line from standard input 
%               and convert it to an integer. Raise Failure "int_of_string"  if
%               the line read is not a valid representation of an integer.
%  
%<<
%  val read_float : unit -> float
%>>
%    
%                Flush standard output, then read one line from standard input 
%               and convert it to a floating-point number.  The result is
%               unspecified if the line read is not a valid  representation of a
%               floating-point number.
%  
%
%General output functions
%------------------------
%  
%<<
%  type open_flag =
%    | Open_rdonly
%>>
%   
%                open for reading. 
%   
%<<
%    | Open_wronly
%>>
%   
%                open for writing. 
%   
%<<
%    | Open_append
%>>
%   
%                open for appending: always write at end of file. 
%   
%<<
%    | Open_creat
%>>
%   
%                create the file if it does not exist. 
%   
%<<
%    | Open_trunc
%>>
%   
%                empty the file if it already exists. 
%   
%<<
%    | Open_excl
%>>
%   
%                fail if Open_creat and the file already exists. 
%   
%<<
%    | Open_binary
%>>
%   
%                open in binary mode (no conversion). 
%   
%<<
%    | Open_text
%>>
%   
%                open in text mode (may perform conversions). 
%   
%<<
%    | Open_nonblock
%>>
%   
%                open in non'blocking mode. 
%    
%                Opening modes for Pervasives.open_out_gen[19.2] and
%               Pervasives.open_in_gen[19.2].
%  
%<<
%  val open_out : string -> out_channel
%>>
%    
%                Open the named file for writing, and return a new output
%               channel  on that file, positionned at the beginning of the file.
%               The  file is truncated to zero length if it already exists. It 
%               is created if it does not already exists.  Raise Sys_error if
%               the file could not be opened.
%  
%<<
%  val open_out_bin : string -> out_channel
%>>
%    
%                Same as Pervasives.open_out[19.2], but the file is opened in
%               binary mode,  so that no translation takes place during writes.
%               On operating  systems that do not distinguish between text mode
%               and binary  mode, this function behaves like
%               Pervasives.open_out[19.2].
%  
%<<
%  val open_out_gen : open_flag list -> int -> string -> out_channel
%>>
%    
%                Open the named file for writing, as above. The extra argument
%               mode  specify the opening mode. The extra argument perm
%               specifies  the file permissions, in case the file must be
%               created.  Pervasives.open_out[19.2] and
%               Pervasives.open_out_bin[19.2] are special  cases of this
%               function.
%  
%<<
%  val flush : out_channel -> unit
%>>
%    
%                Flush the buffer associated with the given output channel,  
%               performing all pending writes on that channel.  Interactive
%               programs must be careful about flushing standard  output and
%               standard error at the right time.
%  
%<<
%  val flush_all : unit -> unit
%>>
%    
%                Flush all open output channels; ignore errors.
%  
%<<
%  val output_char : out_channel -> char -> unit
%>>
%    
%                Write the character on the given output channel.
%  
%<<
%  val output_string : out_channel -> string -> unit
%>>
%    
%                Write the string on the given output channel.
%  
%<<
%  val output : out_channel -> string -> int -> int -> unit
%>>
%    
%                output oc buf pos len writes len characters from string buf, 
%               starting at offset pos, to the given output channel oc.  Raise
%               Invalid_argument "output" if pos and len do not  designate a
%               valid substring of buf.
%  
%<<
%  val output_byte : out_channel -> int -> unit
%>>
%    
%                Write one 8'bit integer (as the single character with that
%               code)  on the given output channel. The given integer is taken
%               modulo  256.
%  
%<<
%  val output_binary_int : out_channel -> int -> unit
%>>
%    
%                Write one integer in binary format (4 bytes, big-endian)  on
%               the given output channel.  The given integer is taken modulo
%               2^32.  The only reliable way to read it back is through the 
%               Pervasives.input_binary_int[19.2] function. The format is
%               compatible across  all machines for a given version of Objective
%               Caml.
%  
%<<
%  val output_value : out_channel -> 'a -> unit
%>>
%    
%                Write the representation of a structured value of any type  to
%               a channel. Circularities and sharing inside the value  are
%               detected and preserved. The object can be read back,  by the
%               function Pervasives.input_value[19.2]. See the description of
%               module  Marshal[20.19] for more information.
%               Pervasives.output_value[19.2] is equivalent  to
%               Marshal.to_channel[20.19] with an empty list of flags.
%  
%<<
%  val seek_out : out_channel -> int -> unit
%>>
%    
%                seek_out chan pos sets the current writing position to pos  for
%               channel chan. This works only for regular files. On  files of
%               other kinds (such as terminals, pipes and sockets),  the
%               behavior is unspecified.
%  
%<<
%  val pos_out : out_channel -> int
%>>
%    
%                Return the current writing position for the given channel. Does
%                not work on channels opened with the Open_append flag (returns 
%               unspecified results).
%  
%<<
%  val out_channel_length : out_channel -> int
%>>
%    
%                Return the size (number of characters) of the regular file  on
%               which the given channel is opened. If the channel is opened  on
%               a file that is not a regular file, the result is meaningless.
%  
%<<
%  val close_out : out_channel -> unit
%>>
%    
%                Close the given channel, flushing all buffered write
%               operations.  Output functions raise a Sys_error exception when
%               they are  applied to a closed output channel, except close_out
%               and flush,  which do nothing when applied to an already closed
%               channel.  Note that close_out may raise Sys_error if the
%               operating  system signals an error when flushing or closing.
%  
%<<
%  val close_out_noerr : out_channel -> unit
%>>
%    
%                Same as close_out, but ignore all errors.
%  
%<<
%  val set_binary_mode_out : out_channel -> bool -> unit
%>>
%    
%                set_binary_mode_out oc true sets the channel oc to binary 
%               mode: no translations take place during output. 
%               set_binary_mode_out oc false sets the channel oc to text  mode:
%               depending on the operating system, some translations  may take
%               place during output. For instance, under Windows,  end-of-lines
%               will be translated from \n to \r\n.  This function has no effect
%               under operating systems that  do not distinguish between text
%               mode and binary mode.
%  
%
%General input functions
%-----------------------
%  
%<<
%  val open_in : string -> in_channel
%>>
%    
%                Open the named file for reading, and return a new input channel
%                on that file, positionned at the beginning of the file.  Raise
%               Sys_error if the file could not be opened.
%  
%<<
%  val open_in_bin : string -> in_channel
%>>
%    
%                Same as Pervasives.open_in[19.2], but the file is opened in
%               binary mode,  so that no translation takes place during reads.
%               On operating  systems that do not distinguish between text mode
%               and binary  mode, this function behaves like
%               Pervasives.open_in[19.2].
%  
%<<
%  val open_in_gen : open_flag list -> int -> string -> in_channel
%>>
%    
%                Open the named file for reading, as above. The extra arguments 
%               mode and perm specify the opening mode and file permissions. 
%               Pervasives.open_in[19.2] and Pervasives.open_in_bin[19.2] are
%               special  cases of this function.
%  
%<<
%  val input_char : in_channel -> char
%>>
%    
%                Read one character from the given input channel.  Raise
%               End_of_file if there are no more characters to read.
%  
%<<
%  val input_line : in_channel -> string
%>>
%    
%                Read characters from the given input channel, until a  newline
%               character is encountered. Return the string of  all characters
%               read, without the newline character at the end.  Raise
%               End_of_file if the end of the file is reached  at the beginning
%               of line.
%  
%<<
%  val input : in_channel -> string -> int -> int -> int
%>>
%    
%                input ic buf pos len reads up to len characters from  the given
%               channel ic, storing them in string buf, starting at  character
%               number pos.  It returns the actual number of characters read,
%               between 0 and  len (inclusive).  A return value of 0 means that
%               the end of file was reached.  A return value between 0 and len
%               exclusive means that  not all requested len characters were
%               read, either because  no more characters were available at that
%               time, or because  the implementation found it convenient to do a
%               partial read;  input must be called again to read the remaining
%               characters,  if desired. (See also Pervasives.really_input[19.2]
%               for reading  exactly len characters.)  Exception
%               Invalid_argument "input" is raised if pos and len  do not
%               designate a valid substring of buf.
%  
%<<
%  val really_input : in_channel -> string -> int -> int -> unit
%>>
%    
%                really_input ic buf pos len reads len characters from channel
%               ic,  storing them in string buf, starting at character number
%               pos.  Raise End_of_file if the end of file is reached before len
%                characters have been read.  Raise Invalid_argument
%               "really_input" if  pos and len do not designate a valid
%               substring of buf.
%  
%<<
%  val input_byte : in_channel -> int
%>>
%    
%                Same as Pervasives.input_char[19.2], but return the 8'bit
%               integer representing  the character.  Raise End_of_file if an
%               end of file was reached.
%  
%<<
%  val input_binary_int : in_channel -> int
%>>
%    
%                Read an integer encoded in binary format (4 bytes, big-endian) 
%               from the given input channel. See
%               Pervasives.output_binary_int[19.2].  Raise End_of_file if an end
%               of file was reached while reading the  integer.
%  
%<<
%  val input_value : in_channel -> 'a
%>>
%    
%                Read the representation of a structured value, as produced  by
%               Pervasives.output_value[19.2], and return the corresponding
%               value.  This function is identical to
%               Marshal.from_channel[20.19];  see the description of module
%               Marshal[20.19] for more information,  in particular concerning
%               the lack of type safety.
%  
%<<
%  val seek_in : in_channel -> int -> unit
%>>
%    
%                seek_in chan pos sets the current reading position to pos  for
%               channel chan. This works only for regular files. On  files of
%               other kinds, the behavior is unspecified.
%  
%<<
%  val pos_in : in_channel -> int
%>>
%    
%                Return the current reading position for the given channel.
%  
%<<
%  val in_channel_length : in_channel -> int
%>>
%    
%                Return the size (number of characters) of the regular file  on
%               which the given channel is opened. If the channel is opened  on
%               a file that is not a regular file, the result is meaningless. 
%               The returned size does not take into account the end-of-line 
%               translations that can be performed when reading from a channel 
%               opened in text mode.
%  
%<<
%  val close_in : in_channel -> unit
%>>
%    
%                Close the given channel. Input functions raise a Sys_error 
%               exception when they are applied to a closed input channel, 
%               except close_in, which does nothing when applied to an already 
%               closed channel. Note that close_in may raise Sys_error if  the
%               operating system signals an error.
%  
%<<
%  val close_in_noerr : in_channel -> unit
%>>
%    
%                Same as close_in, but ignore all errors.
%  
%<<
%  val set_binary_mode_in : in_channel -> bool -> unit
%>>
%    
%                set_binary_mode_in ic true sets the channel ic to binary  mode:
%               no translations take place during input.  set_binary_mode_out ic
%               false sets the channel ic to text  mode: depending on the
%               operating system, some translations  may take place during
%               input. For instance, under Windows,  end-of-lines will be
%               translated from \r\n to \n.  This function has no effect under
%               operating systems that  do not distinguish between text mode and
%               binary mode.
%  
%
%Operations on large files
%-------------------------
%  
%<<
%  module LargeFile : >>
%   
%    sig
% 
%  
%   <<
%     val seek_out : Pervasives.out_channel -> int64 -> unit
%   >>
%  
%   <<
%     val pos_out : Pervasives.out_channel -> int64
%   >>
%  
%   <<
%     val out_channel_length : Pervasives.out_channel -> int64
%   >>
%  
%   <<
%     val seek_in : Pervasives.in_channel -> int64 -> unit
%   >>
%  
%   <<
%     val pos_in : Pervasives.in_channel -> int64
%   >>
%  
%   <<
%     val in_channel_length : Pervasives.in_channel -> int64
%   >>
%   
%  -  end
%  
%                Operations on large files.  This sub-module provides 64'bit
%               variants of the channel functions  that manipulate file
%               positions and file sizes. By representing  positions and sizes
%               by 64'bit integers (type int64) instead of  regular integers
%               (type int), these alternate functions allow  operating on files
%               whose sizes are greater than max_int.
%  
%
References
==========
%  
%<<
  type 'a ref 
%  type 'a ref = {
%    mutable contents : 'a ;
%  }
%>>
%    
%                The type of references (mutable indirection cells) containing 
%               a value of type 'a.
%  
%<<
  val ref : 'a -> 'a ref
%>>
%    
%                Return a fresh reference containing the given value.
%  
%<<
  val (!) : 'a ref -> 'a
%>>
%    
%                !r returns the current contents of reference r.  Equivalent to
%               fun r -> r.contents.
%  
%<<
  val (:=) : 'a ref -> 'a -> unit
%>>
%    
%                r := a stores the value of a in reference r.  Equivalent to fun
%               r v -> r.contents <- v.
%  
%<<
%  val incr : int ref -> unit
%>>
%    
%                Increment the integer contained in the given reference. 
%               Equivalent to fun r -> r := succ !r.
%  
%<<
%  val decr : int ref -> unit
%>>
%    
%                Decrement the integer contained in the given reference. 
%               Equivalent to fun r -> r := pred !r.
%  
%
%Operations on format strings
%============================
%  
%  See modules Printf[20.24] and Scanf[20.27] for more operations on   format
%strings.
%<<
%  type ('a, 'b, 'c) format = ('a, 'b, 'c, 'c) format4 
%>>
%    
%                Simplified type for format strings, included for backward
%               compatibility  with earlier releases of Objective Caml.  'a is
%               the type of the parameters of the format,  'c is the result type
%               for the "printf"-style function,  and 'b is the type of the
%               first argument given to  %a and %t printing functions.
%  
%<<
%  val string_of_format : ('a, 'b, 'c, 'd) format4 -> string
%>>
%    
%                Converts a format string into a string.
%  
%<<
%  val format_of_string : ('a, 'b, 'c, 'd) format4 -> ('a, 'b, 'c, 'd) format4
%>>
%    
%                format_of_string s returns a format string read from the string
%                literal s.
%  
%<<
%  val (^^) :
%    ('a, 'b, 'c, 'd) format4 ->
%    (-d, 'b, 'c, -e) format4 -> ('a, 'b, 'c, -e) format4
%>>
%    
%                f1 ^^f2 catenates formats f1 and f2. The result is a format 
%               that accepts arguments from f1, then arguments from f2.
%  
%
%Program termination
%===================
%  
%<<
%  val exit : int -> 'a
%>>
%    
%                Terminate the process, returning the given status code  to the
%               operating system: usually 0 to indicate no errors,  and a small
%               positive integer to indicate failure.   All open output channels
%               are flushed with flush_all.  An implicit exit 0 is performed
%               each time a program  terminates normally. An implicit exit 2 is
%               performed if the program  terminates early because of an
%               uncaught exception.
%  
%<<
%  val at_exit : (unit -> unit) -> unit
%>>
%    
%                Register the given function to be called at program 
%               termination time. The functions registered with at_exit  will be
%               called when the program executes Pervasives.exit[19.2],  or
%               terminates, either normally or because of an uncaught exception.
%                The functions are called in --last in, first out-- order:  the
%               function most recently added with at_exit is called first.
%  
%   
%   
%  
%
%Chapter 20    The standard library
%**********************************
%    
%  This chapter describes the functions provided by the Objective Caml standard
%library. The modules from the standard library are automatically linked with
%the user-s object code files by the ocamlc command. Hence, these modules can be
%used in standalone programs without having to add any .cmo file on the command
%line for the linking phase. Similarly, in interactive use, these globals can be
%used in toplevel phrases without having to load any .cmo file in memory.
%  Unlike the Pervasive module from the core library, the modules from the
%standard library are not automatically --opened-- when a compilation starts, or
%when the toplevel system is launched. Hence it is necessary to use qualified
%identifiers to refer to the functions provided by these modules, or to add open
%directives.
%  
%
%Conventions
%*=*=*=*=*=*
%
%  
%  For easy reference, the modules are listed below in alphabetical order of
%module names. For each module, the declarations from its signature are printed
%one by one in typewriter font, followed by a short comment. All modules and the
%identifiers they export are indexed at the end of this report.
%  
%  
%
%20.1  Module Arg : Parsing of command line arguments.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  This module provides a general mechanism for extracting options and 
%arguments from the command line to the program.
%  Syntax of command lines:  A keyword is a character string starting with a -. 
%An option is a keyword alone or followed by an argument.  The types of keywords
%are: Unit, Bool, Set, Clear,  String, Set_string, Int, Set_int, Float,
%Set_float,  Tuple, Symbol, and Rest.  Unit, Set and Clear keywords take no
%argument. A Rest  keyword takes the remaining of the command line as arguments.
% Every other keyword takes the following word on the command line  as argument.
% Arguments not preceded by a keyword are called anonymous arguments.
%  Examples (cmd is assumed to be the command name):
%  
% - cmd -flag (a unit option) 
% - cmd -int 1 (an int option with argument 1) 
% - cmd -string foobar (a string option with argument "foobar") 
% - cmd -float 12.34 (a float option with argument 12.34) 
% - cmd a b c (three anonymous arguments: "a", "b", and "c") 
% - cmd a b -- c d (two anonymous arguments and a rest option with  two
%   arguments) 
%  
%  0.5cm
%<<
%  type spec =
%    | Unit of (unit -> unit)
%>>
%   
%                Call the function with unit argument 
%   
%<<
%    | Bool of (bool -> unit)
%>>
%   
%                Call the function with a bool argument 
%   
%<<
%    | Set of bool Pervasives.ref
%>>
%   
%                Set the reference to true 
%   
%<<
%    | Clear of bool Pervasives.ref
%>>
%   
%                Set the reference to false 
%   
%<<
%    | String of (string -> unit)
%>>
%   
%                Call the function with a string argument 
%   
%<<
%    | Set_string of string Pervasives.ref
%>>
%   
%                Set the reference to the string argument 
%   
%<<
%    | Int of (int -> unit)
%>>
%   
%                Call the function with an int argument 
%   
%<<
%    | Set_int of int Pervasives.ref
%>>
%   
%                Set the reference to the int argument 
%   
%<<
%    | Float of (float -> unit)
%>>
%   
%                Call the function with a float argument 
%   
%<<
%    | Set_float of float Pervasives.ref
%>>
%   
%                Set the reference to the float argument 
%   
%<<
%    | Tuple of spec list
%>>
%   
%                Take several arguments according to the  spec list 
%   
%<<
%    | Symbol of string list * (string -> unit)
%>>
%   
%                Take one of the symbols as argument and  call the function with
%               the symbol 
%   
%<<
%    | Rest of (string -> unit)
%>>
%   
%                Stop interpreting keywords and call the   function with each
%               remaining argument 
%    
%                The concrete type describing the behavior associated  with a
%               keyword.
%  
%<<
%  type key = string 
%>>
%   
%<<
%  type doc = string 
%>>
%   
%<<
%  type usage_msg = string 
%>>
%   
%<<
%  type anon_fun = string -> unit 
%>>
%   
%<<
%  val parse : (key * spec * doc) list -> anon_fun -> usage_msg -> unit
%>>
%    
%                Arg.parse speclist anon_fun usage_msg parses the command line. 
%               speclist is a list of triples (key, spec, doc).  key is the
%               option keyword, it must start with a --- character.  spec gives
%               the option type and the function to call when this option  is
%               found on the command line.  doc is a one-line description of
%               this option.  anon_fun is called on anonymous arguments.  The
%               functions in spec and anon_fun are called in the same order  as
%               their arguments appear on the command line.
%               If an error occurs, Arg.parse exits the program, after printing 
%               an error message as follows:
%                 
%                - The reason for the error: unknown option, invalid or missing
%                  argument, etc. 
%                - usage_msg 
%                - The list of options, each followed by the corresponding doc
%                  string. 
%               
%               For the user to be able to specify anonymous arguments starting
%               with a  -, include for example ("-", String anon_fun, doc) in
%               speclist.
%               By default, parse recognizes two unit options, -help and --help,
%                which will display usage_msg and the list of options, and exit 
%               the program. You can override this behaviour by specifying your 
%               own -help and --help options in speclist.
%  
%<<
%  val parse_argv :
%    ?current:int Pervasives.ref ->
%    string array ->
%    (key * spec * doc) list -> anon_fun -> usage_msg -> unit
%>>
%    
%                Arg.parse_argv ~current args speclist anon_fun usage_msg parses
%                the array args as if it were the command line. It uses and
%               updates  the value of ~current (if given), or Arg.current. You
%               must set  it before calling parse_argv. The initial value of
%               current  is the index of the program name (argument 0) in the
%               array.  If an error occurs, Arg.parse_argv raises Arg.Bad with 
%               the error message as argument. If option -help or --help is 
%               given, Arg.parse_argv raises Arg.Help with the help message  as
%               argument.
%  
%<<
%  exception Help of string
%>>
%    
%                Raised by Arg.parse_argv when the user asks for help.
%  
%<<
%  exception Bad of string
%>>
%    
%                Functions in spec or anon_fun can raise Arg.Bad with an error 
%               message to reject invalid arguments.  Arg.Bad is also raised by
%               Arg.parse_argv in case of an error.
%  
%<<
%  val usage : (key * spec * doc) list -> usage_msg -> unit
%>>
%    
%                Arg.usage speclist usage_msg prints an error message including 
%               the list of valid options. This is the same message that 
%               Arg.parse[20.1] prints in case of error.  speclist and usage_msg
%               are the same as for Arg.parse.
%  
%<<
%  val align : (key * spec * doc) list -> (key * spec * doc) list
%>>
%    
%                Align the documentation strings by inserting spaces at the
%               first  space, according to the length of the keyword. Use a 
%               space as the first character in a doc string if you want to 
%               align the whole string. The doc strings corresponding to  Symbol
%               arguments are not aligned.
%  
%<<
%  val current : int Pervasives.ref
%>>
%    
%                Position (in Sys.argv[20.34]) of the argument being processed.
%               You can  change this value, e.g. to force Arg.parse[20.1] to
%               skip some arguments.  Arg.parse[20.1] uses the initial value of
%               Arg.current[20.1] as the index of  argument 0 (the program name)
%               and starts parsing arguments  at the next element.
%  
%
%
%20.2  Module Array : Array operations.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  val length : 'a array -> int
%>>
%    
%                Return the length (number of elements) of the given array.
%  
%<<
%  val get : 'a array -> int -> 'a
%>>
%    
%                Array.get a n returns the element number n of array a.  The
%               first element has number 0.  The last element has number
%               Array.length a - 1.  You can also write a.(n) instead of
%               Array.get a n. 
%               Raise Invalid_argument "index out of bounds"  if n is outside
%               the range 0 to (Array.length a - 1).
%  
%<<
%  val set : 'a array -> int -> 'a -> unit
%>>
%    
%                Array.set a n x modifies array a in place, replacing  element
%               number n with x.  You can also write a.(n) <- x instead of
%               Array.set a n x.
%               Raise Invalid_argument "index out of bounds"  if n is outside
%               the range 0 to Array.length a - 1.
%  
%<<
%  val make : int -> 'a -> 'a array
%>>
%    
%                Array.make n x returns a fresh array of length n,  initialized
%               with x.  All the elements of this new array are initially 
%               physically equal to x (in the sense of the == predicate). 
%               Consequently, if x is mutable, it is shared among all elements 
%               of the array, and modifying x through one of the array entries 
%               will modify all other entries at the same time.
%               Raise Invalid_argument if n < 0 or n > Sys.max_array_length.  If
%               the value of x is a floating-point number, then the maximum 
%               size is only Sys.max_array_length / 2.
%  
%<<
%  val create : int -> 'a -> 'a array
%>>
%    
%                Deprecated. Array.create is an alias for Array.make[20.2]. 
%  
%<<
%  val init : int -> (int -> 'a) -> 'a array
%>>
%    
%                Array.init n f returns a fresh array of length n,  with element
%               number i initialized to the result of f i.  In other terms,
%               Array.init n f tabulates the results of f  applied to the
%               integers 0 to n-1.
%               Raise Invalid_argument if n < 0 or n > Sys.max_array_length.  If
%               the return type of f is float, then the maximum  size is only
%               Sys.max_array_length / 2.
%  
%<<
%  val make_matrix : int -> int -> 'a -> 'a array array
%>>
%    
%                Array.make_matrix dimx dimy e returns a two-dimensional array 
%               (an array of arrays) with first dimension dimx and  second
%               dimension dimy. All the elements of this new matrix  are
%               initially physically equal to e.  The element (x,y) of a matrix
%               m is accessed  with the notation m.(x).(y).
%               Raise Invalid_argument if dimx or dimy is negative or  greater
%               than Sys.max_array_length.  If the value of e is a
%               floating-point number, then the maximum  size is only
%               Sys.max_array_length / 2.
%  
%<<
%  val create_matrix : int -> int -> 'a -> 'a array array
%>>
%    
%                Deprecated. Array.create_matrix is an alias for
%               Array.make_matrix[20.2]. 
%  
%<<
%  val append : 'a array -> 'a array -> 'a array
%>>
%    
%                Array.append v1 v2 returns a fresh array containing the 
%               concatenation of the arrays v1 and v2.
%  
%<<
%  val concat : 'a array list -> 'a array
%>>
%    
%                Same as Array.append, but concatenates a list of arrays.
%  
%<<
%  val sub : 'a array -> int -> int -> 'a array
%>>
%    
%                Array.sub a start len returns a fresh array of length len, 
%               containing the elements number start to start + len - 1  of
%               array a.
%               Raise Invalid_argument "Array.sub" if start and len do not 
%               designate a valid subarray of a; that is, if  start < 0, or len
%               < 0, or start + len > Array.length a.
%  
%<<
%  val copy : 'a array -> 'a array
%>>
%    
%                Array.copy a returns a copy of a, that is, a fresh array 
%               containing the same elements as a.
%  
%<<
%  val fill : 'a array -> int -> int -> 'a -> unit
%>>
%    
%                Array.fill a ofs len x modifies the array a in place,  storing
%               x in elements number ofs to ofs + len - 1.
%               Raise Invalid_argument "Array.fill" if ofs and len do not 
%               designate a valid subarray of a.
%  
%<<
%  val blit : 'a array -> int -> 'a array -> int -> int -> unit
%>>
%    
%                Array.blit v1 o1 v2 o2 len copies len elements  from array v1,
%               starting at element number o1, to array v2,  starting at element
%               number o2. It works correctly even if  v1 and v2 are the same
%               array, and the source and  destination chunks overlap.
%               Raise Invalid_argument "Array.blit" if o1 and len do not 
%               designate a valid subarray of v1, or if o2 and len do not 
%               designate a valid subarray of v2.
%  
%<<
%  val to_list : 'a array -> 'a list
%>>
%    
%                Array.to_list a returns the list of all the elements of a.
%  
%<<
%  val of_list : 'a list -> 'a array
%>>
%    
%                Array.of_list l returns a fresh array containing the elements 
%               of l.
%  
%<<
%  val iter : ('a -> unit) -> 'a array -> unit
%>>
%    
%                Array.iter f a applies function f in turn to all  the elements
%               of a. It is equivalent to  f a.(0); f a.(1); ...; f
%               a.(Array.length a - 1); ().
%  
%<<
%  val map : ('a -> 'b) -> 'a array -> 'b array
%>>
%    
%                Array.map f a applies function f to all the elements of a,  and
%               builds an array with the results returned by f:  [| f a.(0); f
%               a.(1); ...; f a.(Array.length a - 1) |].
%  
%<<
%  val iteri : (int -> 'a -> unit) -> 'a array -> unit
%>>
%    
%                Same as Array.iter[20.2], but the  function is applied to the
%               index of the element as first argument,  and the element itself
%               as second argument.
%  
%<<
%  val mapi : (int -> 'a -> 'b) -> 'a array -> 'b array
%>>
%    
%                Same as Array.map[20.2], but the  function is applied to the
%               index of the element as first argument,  and the element itself
%               as second argument.
%  
%<<
%  val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b array -> 'a
%>>
%    
%                Array.fold_left f x a computes  f (... (f (f x a.(0)) a.(1))
%               ...) a.(n-1),  where n is the length of the array a.
%  
%<<
%  val fold_right : ('a -> 'b -> 'b) -> 'a array -> 'b -> 'b
%>>
%    
%                Array.fold_right f a x computes  f a.(0) (f a.(1) ( ... (f
%               a.(n-1) x) ...)),  where n is the length of the array a.
%  
%
%Sorting
%=======
%  
%<<
%  val sort : ('a -> 'a -> int) -> 'a array -> unit
%>>
%    
%                Sort an array in increasing order according to a comparison 
%               function. The comparison function must return 0 if its arguments
%                compare as equal, a positive integer if the first is greater, 
%               and a negative integer if the first is smaller (see below for a 
%               complete specification). For example, Pervasives.compare[19.2]
%               is  a suitable comparison function, provided there are no
%               floating-point  NaN values in the data. After calling
%               Array.sort, the  array is sorted in place in increasing order. 
%               Array.sort is guaranteed to run in constant heap space  and (at
%               most) logarithmic stack space.
%               The current implementation uses Heap Sort. It runs in constant 
%               stack space.
%               Specification of the comparison function:  Let a be the array
%               and cmp the comparison function. The following  must be true for
%               all x, y, z in a :
%                 
%                - cmp x y > 0 if and only if cmp y x < 0 
%                - if cmp x y >= 0 and cmp y z >= 0 then cmp x z >= 0 
%               
%               When Array.sort returns, a contains the same elements as before,
%                reordered in such a way that for all i and j valid indices of a
%               :
%                 
%                - cmp a.(i) a.(j) >= 0 if and only if i >= j 
%  
%<<
%  val stable_sort : ('a -> 'a -> int) -> 'a array -> unit
%>>
%    
%                Same as Array.sort[20.2], but the sorting algorithm is stable
%               (i.e.  elements that compare equal are kept in their original
%               order) and  not guaranteed to run in constant heap space.
%               The current implementation uses Merge Sort. It uses n/2  words
%               of heap space, where n is the length of the array.  It is
%               usually faster than the current implementation of
%               Array.sort[20.2].
%  
%<<
%  val fast_sort : ('a -> 'a -> int) -> 'a array -> unit
%>>
%    
%                Same as Array.sort[20.2] or Array.stable_sort[20.2], whichever
%               is faster  on typical input.
%  
%
%
%20.3  Module Buffer : Extensible string buffers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module implements string buffers that automatically expand  as
%necessary. It provides accumulative concatenation of strings  in quasi-linear
%time (instead of quadratic time when strings are  concatenated pairwise).
%  0.5cm
%<<
%  type t 
%>>
%    
%                The abstract type of buffers.
%  
%<<
%  val create : int -> t
%>>
%    
%                create n returns a fresh buffer, initially empty.  The n
%               parameter is the initial size of the internal string  that holds
%               the buffer contents. That string is automatically  reallocated
%               when more than n characters are stored in the buffer,  but
%               shrinks back to n characters when reset is called.  For best
%               performance, n should be of the same order of magnitude  as the
%               number of characters that are expected to be stored in  the
%               buffer (for instance, 80 for a buffer that holds one output 
%               line). Nothing bad will happen if the buffer grows beyond that 
%               limit, however. In doubt, take n = 16 for instance.  If n is not
%               between 1 and Sys.max_string_length[20.34], it will  be clipped
%               to that interval.
%  
%<<
%  val contents : t -> string
%>>
%    
%                Return a copy of the current contents of the buffer.  The
%               buffer itself is unchanged.
%  
%<<
%  val sub : t -> int -> int -> string
%>>
%    
%                Buffer.sub b off len returns (a copy of) the substring of the
%               current contents of the buffer b starting at offset off of
%               length len bytes. May raise Invalid_argument if out of bounds
%               request. The buffer itself is unaffected.
%  
%<<
%  val nth : t -> int -> char
%>>
%    
%                get the n-th character of the buffer. Raise Invalid_argument if
%               index out of bounds
%  
%<<
%  val length : t -> int
%>>
%    
%                Return the number of characters currently contained in the
%               buffer.
%  
%<<
%  val clear : t -> unit
%>>
%    
%                Empty the buffer.
%  
%<<
%  val reset : t -> unit
%>>
%    
%                Empty the buffer and deallocate the internal string holding the
%                buffer contents, replacing it with the initial internal string 
%               of length n that was allocated by Buffer.create[20.3] n.  For
%               long-lived buffers that may have grown a lot, reset allows 
%               faster reclamation of the space used by the buffer.
%  
%<<
%  val add_char : t -> char -> unit
%>>
%    
%                add_char b c appends the character c at the end of the buffer
%               b.
%  
%<<
%  val add_string : t -> string -> unit
%>>
%    
%                add_string b s appends the string s at the end of the buffer b.
%  
%<<
%  val add_substring : t -> string -> int -> int -> unit
%>>
%    
%                add_substring b s ofs len takes len characters from offset  ofs
%               in string s and appends them at the end of the buffer b.
%  
%<<
%  val add_substitute : t -> (string -> string) -> string -> unit
%>>
%    
%                add_substitute b f s appends the string pattern s at the end 
%               of the buffer b with substitution.  The substitution process
%               looks for variables into  the pattern and substitutes each
%               variable name by its value, as  obtained by applying the mapping
%               f to the variable name. Inside the  string pattern, a variable
%               name immediately follows a non-escaped  $ character and is one
%               of the following:
%                 
%                - a non empty sequence of alphanumeric or _ characters, 
%                - an arbitrary sequence of characters enclosed by a pair of 
%                  matching parentheses or curly brackets.  An escaped $
%                  character is a $ that immediately follows a backslash 
%                  character; it then stands for a plain $.  Raise Not_found if
%                  the closing character of a parenthesized variable  cannot be
%                  found. 
%  
%<<
%  val add_buffer : t -> t -> unit
%>>
%    
%                add_buffer b1 b2 appends the current contents of buffer b2  at
%               the end of buffer b1. b2 is not modified.
%  
%<<
%  val add_channel : t -> Pervasives.in_channel -> int -> unit
%>>
%    
%                add_channel b ic n reads exactly n character from the  input
%               channel ic and stores them at the end of buffer b.  Raise
%               End_of_file if the channel contains fewer than n  characters.
%  
%<<
%  val output_buffer : Pervasives.out_channel -> t -> unit
%>>
%    
%                output_buffer oc b writes the current contents of buffer b  on
%               the output channel oc.
%  
%
%
%20.4  Module Callback : Registering Caml values with the C runtime.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  This module allows Caml values to be registered with the C runtime  under a
%symbolic name, so that C code can later call back registered  Caml functions,
%or raise registered Caml exceptions.
%  0.5cm
%<<
%  val register : string -> 'a -> unit
%>>
%    
%                Callback.register n v registers the value v under  the name n.
%               C code can later retrieve a handle to v  by calling
%               caml_named_value(n).
%  
%<<
%  val register_exception : string -> exn -> unit
%>>
%    
%                Callback.register_exception n exn registers the  exception
%               contained in the exception value exn  under the name n. C code
%               can later retrieve a handle to  the exception by calling
%               caml_named_value(n). The exception  value thus obtained is
%               suitable for passign as first argument  to raise_constant or
%               raise_with_arg.
%  
%
%
%20.5  Module Char : Character operations.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%<<
%  val code : char -> int
%>>
%    
%                Return the ASCII code of the argument.
%  
%<<
%  val chr : int -> char
%>>
%    
%                Return the character with the given ASCII code.  Raise
%               Invalid_argument "Char.chr" if the argument is  outside the
%               range 0--255.
%  
%<<
%  val escaped : char -> string
%>>
%    
%                Return a string representing the given character,  with special
%               characters escaped following the lexical conventions  of
%               Objective Caml.
%  
%<<
%  val lowercase : char -> char
%>>
%    
%                Convert the given character to its equivalent lowercase
%               character.
%  
%<<
%  val uppercase : char -> char
%>>
%    
%                Convert the given character to its equivalent uppercase
%               character.
%  
%<<
%  type t = char 
%>>
%    
%                An alias for the type of characters.
%  
%<<
%  val compare : t -> t -> int
%>>
%    
%                The comparison function for characters, with the same
%               specification as  Pervasives.compare[19.2]. Along with the type
%               t, this function compare  allows the module Char to be passed as
%               argument to the functors  Set.Make[20.28] and Map.Make[20.18].
%  
%
%
%20.6  Module Complex : Complex numbers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  This module provides arithmetic operations on complex numbers.  Complex
%numbers are represented by their real and imaginary parts  (cartesian
%representation). Each part is represented by a  double-precision floating-point
%number (type float).
%  0.5cm
%<<
%  type t = {
%    re : float ;
%    im : float ;
%  }
%>>
%    
%                The type of complex numbers. re is the real part and im the 
%               imaginary part.
%  
%<<
%  val zero : t
%>>
%    
%                The complex number 0.
%  
%<<
%  val one : t
%>>
%    
%                The complex number 1.
%  
%<<
%  val i : t
%>>
%    
%                The complex number i.
%  
%<<
%  val neg : t -> t
%>>
%    
%                Unary negation.
%  
%<<
%  val conj : t -> t
%>>
%    
%                Conjugate: given the complex x + i.y, returns x - i.y.
%  
%<<
%  val add : t -> t -> t
%>>
%    
%                Addition
%  
%<<
%  val sub : t -> t -> t
%>>
%    
%                Subtraction
%  
%<<
%  val mul : t -> t -> t
%>>
%    
%                Multiplication
%  
%<<
%  val inv : t -> t
%>>
%    
%                Multiplicative inverse (1/z).
%  
%<<
%  val div : t -> t -> t
%>>
%    
%                Division
%  
%<<
%  val sqrt : t -> t
%>>
%    
%                Square root. The result x + i.y is such that x > 0 or  x = 0
%               and y >= 0.  This function has a discontinuity along the
%               negative real axis.
%  
%<<
%  val norm2 : t -> float
%>>
%    
%                Norm squared: given x + i.y, returns x^2 + y^2.
%  
%<<
%  val norm : t -> float
%>>
%    
%                Norm: given x + i.y, returns sqrt(x^2 + y^2).
%  
%<<
%  val arg : t -> float
%>>
%    
%                Argument. The argument of a complex number is the angle  in the
%               complex plane between the positive real axis and a line  passing
%               through zero and the number. This angle ranges from  -pi to pi.
%               This function has a discontinuity along the  negative real axis.
%  
%<<
%  val polar : float -> float -> t
%>>
%    
%                polar norm arg returns the complex having norm norm   and
%               argument arg.
%  
%<<
%  val exp : t -> t
%>>
%    
%                Exponentiation. exp z returns e to the z power.
%  
%<<
%  val log : t -> t
%>>
%    
%                Natural logarithm (in base e).
%  
%<<
%  val pow : t -> t -> t
%>>
%    
%                Power function. pow z1 z2 returns z1 to the z2 power.
%  
%
%
%20.7  Module Digest : MD5 message digest.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  This module provides functions to compute 128'bit --digests-- of 
%arbitrary-length strings or files. The digests are of cryptographic  quality:
%it is very hard, given a digest, to forge a string having  that digest. The
%algorithm used is MD5.
%  0.5cm
%<<
%  type t = string 
%>>
%    
%                The type of digests: 16'character strings.
%  
%<<
%  val string : string -> t
%>>
%    
%                Return the digest of the given string.
%  
%<<
%  val substring : string -> int -> int -> t
%>>
%    
%                Digest.substring s ofs len returns the digest of the substring 
%               of s starting at character number ofs and containing len 
%               characters.
%  
%<<
%  val channel : Pervasives.in_channel -> int -> t
%>>
%    
%                If len is nonnegative, Digest.channel ic len reads len 
%               characters from channel ic and returns their digest, or raises 
%               End_of_file if end-of-file is reached before len characters  are
%               read. If len is negative, Digest.channel ic len reads  all
%               characters from ic until end-of-file is reached and return 
%               their digest.
%  
%<<
%  val file : string -> t
%>>
%    
%                Return the digest of the file whose name is given.
%  
%<<
%  val output : Pervasives.out_channel -> t -> unit
%>>
%    
%                Write a digest on the given output channel.
%  
%<<
%  val input : Pervasives.in_channel -> t
%>>
%    
%                Read a digest from the given input channel.
%  
%<<
%  val to_hex : t -> string
%>>
%    
%                Return the printable hexadecimal representation of the given
%               digest.
%  
%
%
%20.8  Module Filename : Operations on file names.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%<<
%  val current_dir_name : string
%>>
%    
%                The conventional name for the current directory (e.g. . in
%               Unix).
%  
%<<
%  val parent_dir_name : string
%>>
%    
%                The conventional name for the parent of the current directory 
%               (e.g. .. in Unix).
%  
%<<
%  val concat : string -> string -> string
%>>
%    
%                concat dir file returns a file name that designates file  file
%               in directory dir.
%  
%<<
%  val is_relative : string -> bool
%>>
%    
%                Return true if the file name is relative to the current 
%               directory, false if it is absolute (i.e. in Unix, starts  with
%               /).
%  
%<<
%  val is_implicit : string -> bool
%>>
%    
%                Return true if the file name is relative and does not start 
%               with an explicit reference to the current directory (./ or  ../
%               in Unix), false if it starts with an explicit reference  to the
%               root directory or the current directory.
%  
%<<
%  val check_suffix : string -> string -> bool
%>>
%    
%                check_suffix name suff returns true if the filename name  ends
%               with the suffix suff.
%  
%<<
%  val chop_suffix : string -> string -> string
%>>
%    
%                chop_suffix name suff removes the suffix suff from  the
%               filename name. The behavior is undefined if name does not  end
%               with the suffix suff.
%  
%<<
%  val chop_extension : string -> string
%>>
%    
%                Return the given file name without its extension. The extension
%                is the shortest suffix starting with a period and not including
%                a directory separator, .xyz for instance.
%               Raise Invalid_argument if the given name does not contain  an
%               extension.
%  
%<<
%  val basename : string -> string
%>>
%    
%                Split a file name into directory name / base file name.  concat
%               (dirname name) (basename name) returns a file name  which is
%               equivalent to name. Moreover, after setting the  current
%               directory to dirname name (with Sys.chdir[20.34]),  references
%               to basename name (which is a relative file name)  designate the
%               same file as name before the call to Sys.chdir[20.34].
%               The result is not specified if the argument is not a valid file
%               name  (for example, under Unix if there is a NUL character in
%               the string).
%  
%<<
%  val dirname : string -> string
%>>
%    
%                See Filename.basename[20.8].
%  
%<<
%  val temp_file : string -> string -> string
%>>
%    
%                temp_file prefix suffix returns the name of a  fresh temporary
%               file in the temporary directory.  The base name of the temporary
%               file is formed by concatenating  prefix, then a suitably chosen
%               integer number, then suffix.  The temporary file is created
%               empty, with permissions 0o600  (readable and writable only by
%               the file owner). The file is  guaranteed to be different from
%               any other file that existed when  temp_file was called.  Under
%               Unix, the temporary directory is /tmp by default; if set,  the
%               value of the environment variable TMPDIR is used instead.  Under
%               Windows, the name of the temporary directory is the  value of
%               the environment variable TEMP, or C:\temp by default.
%  
%<<
%  val open_temp_file :
%    ?mode:Pervasives.open_flag list ->
%    string -> string -> string * Pervasives.out_channel
%>>
%    
%                Same as Filename.temp_file[20.8], but returns both the name of
%               a fresh  temporary file, and an output channel opened
%               (atomically) on  this file. This function is more secure than
%               temp_file: there  is no risk that the temporary file will be
%               modified (e.g. replaced  by a symbolic link) before the program
%               opens it. The optional argument  mode is a list of additional
%               flags to control the opening of the file.  It can contain one or
%               several of Open_append, Open_binary,  and Open_text. The default
%               is [Open_text] (open in text mode).
%  
%<<
%  val quote : string -> string
%>>
%    
%                Return a quoted version of a file name, suitable for use as 
%               one argument in a shell command line, escaping all shell 
%               meta'characters.
%  
%
%
%20.9  Module Format : Pretty printing.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module implements a pretty-printing facility to format text  within
%--pretty-printing boxes--. The pretty-printer breaks lines  at specified break
%hints, and indents lines according to the box  structure.
%  For a gentle introduction to the basics of pretty-printing using  Format,
%read 
%http://caml.inria.fr/resources/doc/guides/format.html[http://caml.inria.fr/reso
%urces/doc/guides/format.html].
%  Warning: the material output by the following functions is delayed  in the
%pretty-printer queue in order to compute the proper line  breaking. Hence, you
%should not mix calls to the printing functions  of the basic I/O system with
%calls to the functions of this module:  this could result in some strange
%output seemingly unrelated with  the evaluation order of printing commands.
%  You may consider this module as providing an extension to the  printf
%facility to provide automatic line breaking. The addition of  pretty-printing
%annotations to your regular printf formats gives you  fancy indentation and
%line breaks.  Pretty-printing annotations are described below in the
%documentation of  the function Format.fprintf[20.9].
%  You may also use the explicit box management and printing functions  provided
%by this module. This style is more basic but more verbose  than the fprintf
%concise formats.
%  For instance, the sequence  open_box 0; print_string "x ="; print_space ();
%print_int 1; close_box ()  that prints x = 1 within a pretty-printing box, can
%be  abbreviated as printf "@[%s@ %i@]" "x =" 1, or even shorter  printf "@[x =@
%%i@]" 1.
%  Rule of thumb for casual users of this library:
%  
% - use simple boxes (as obtained by open_box 0); 
% - use simple break hints (as obtained by print_cut () that outputs a  simple
%   break hint, or by print_space () that outputs a space  indicating a break
%   hint); 
% - once a box is opened, display its material with basic printing  functions
%   (e. g. print_int and print_string); 
% - when the material for a box has been printed, call close_box () to  close
%   the box; 
% - at the end of your routine, evaluate print_newline () to close  all
%   remaining boxes and flush the pretty-printer. 
%  
%  The behaviour of pretty-printing commands is unspecified  if there is no
%opened pretty-printing box. Each box opened via  one of the open_ functions
%below must be closed using close_box  for proper formatting. Otherwise, some of
%the material printed in the  boxes may not be output, or may be formatted
%incorrectly.
%  In case of interactive use, the system closes all opened boxes and  flushes
%all pending text (as with the print_newline function)  after each phrase. Each
%phrase is therefore executed in the initial  state of the pretty-printer.
%  0.5cm
%
%Boxes
%=====
%  
%<<
%  val open_box : int -> unit
%>>
%    
%                open_box d opens a new pretty-printing box  with offset d. 
%               This box is the general purpose pretty-printing box.  Material
%               in this box is displayed --horizontal or vertical--:  break
%               hints inside the box may lead to a new line, if there  is no
%               more room on the line to print the remainder of the box,  or if
%               a new line may lead to a new indentation  (demonstrating the
%               indentation of the box).  When a new line is printed in the box,
%               d is added to the  current indentation.
%  
%<<
%  val close_box : unit -> unit
%>>
%    
%                Closes the most recently opened pretty-printing box.
%  
%
%Formatting functions
%====================
%  
%<<
%  val print_string : string -> unit
%>>
%    
%                print_string str prints str in the current box.
%  
%<<
%  val print_as : int -> string -> unit
%>>
%    
%                print_as len str prints str in the  current box. The
%               pretty-printer formats str as if  it were of length len.
%  
%<<
%  val print_int : int -> unit
%>>
%    
%                Prints an integer in the current box.
%  
%<<
%  val print_float : float -> unit
%>>
%    
%                Prints a floating point number in the current box.
%  
%<<
%  val print_char : char -> unit
%>>
%    
%                Prints a character in the current box.
%  
%<<
%  val print_bool : bool -> unit
%>>
%    
%                Prints a boolean in the current box.
%  
%
%Break hints
%===========
%  
%<<
%  val print_space : unit -> unit
%>>
%    
%                print_space () is used to separate items (typically to print  a
%               space between two words).  It indicates that the line may be
%               split at this  point. It either prints one space or splits the
%               line.  It is equivalent to print_break 1 0.
%  
%<<
%  val print_cut : unit -> unit
%>>
%    
%                print_cut () is used to mark a good break position.  It
%               indicates that the line may be split at this  point. It either
%               prints nothing or splits the line.  This allows line splitting
%               at the current  point, without printing spaces or adding
%               indentation.  It is equivalent to print_break 0 0.
%  
%<<
%  val print_break : int -> int -> unit
%>>
%    
%                Inserts a break hint in a pretty-printing box.  print_break
%               nspaces offset indicates that the line may  be split (a newline
%               character is printed) at this point,  if the contents of the
%               current box does not fit on the  current line.  If the line is
%               split at that point, offset is added to  the current
%               indentation. If the line is not split,  nspaces spaces are
%               printed.
%  
%<<
%  val print_flush : unit -> unit
%>>
%    
%                Flushes the pretty printer: all opened boxes are closed,  and
%               all pending text is displayed.
%  
%<<
%  val print_newline : unit -> unit
%>>
%    
%                Equivalent to print_flush followed by a new line.
%  
%<<
%  val force_newline : unit -> unit
%>>
%    
%                Forces a newline in the current box. Not the normal way of 
%               pretty-printing, you should prefer break hints.
%  
%<<
%  val print_if_newline : unit -> unit
%>>
%    
%                Executes the next formatting command if the preceding line  has
%               just been split. Otherwise, ignore the next formatting  command.
%  
%
%Margin
%======
%  
%<<
%  val set_margin : int -> unit
%>>
%    
%                set_margin d sets the value of the right margin  to d (in
%               characters): this value is used to detect line  overflows that
%               leads to split lines.  Nothing happens if d is smaller than 2. 
%               If d is too large, the right margin is set to the maximum 
%               admissible value (which is greater than 10^10).
%  
%<<
%  val get_margin : unit -> int
%>>
%    
%                Returns the position of the right margin.
%  
%
%Maximum indentation limit
%=========================
%  
%<<
%  val set_max_indent : int -> unit
%>>
%    
%                set_max_indent d sets the value of the maximum  indentation
%               limit to d (in characters):  once this limit is reached, boxes
%               are rejected to the left,  if they do not fit on the current
%               line.  Nothing happens if d is smaller than 2.  If d is too
%               large, the limit is set to the maximum  admissible value (which
%               is greater than 10^10).
%  
%<<
%  val get_max_indent : unit -> int
%>>
%    
%                Return the value of the maximum indentation limit (in
%               characters).
%  
%
%Formatting depth: maximum number of boxes allowed before ellipsis
%=================================================================
%  
%<<
%  val set_max_boxes : int -> unit
%>>
%    
%                set_max_boxes max sets the maximum number  of boxes
%               simultaneously opened.  Material inside boxes nested deeper is
%               printed as an  ellipsis (more precisely as the text returned by 
%               get_ellipsis_text ()).  Nothing happens if max is smaller than
%               2.
%  
%<<
%  val get_max_boxes : unit -> int
%>>
%    
%                Returns the maximum number of boxes allowed before ellipsis.
%  
%<<
%  val over_max_boxes : unit -> bool
%>>
%    
%                Tests if the maximum number of boxes allowed have already been
%               opened.
%  
%
%Advanced formatting
%===================
%  
%<<
%  val open_hbox : unit -> unit
%>>
%    
%                open_hbox () opens a new pretty-printing box.  This box is
%               --horizontal--: the line is not split in this box  (new lines
%               may still occur inside boxes nested deeper).
%  
%<<
%  val open_vbox : int -> unit
%>>
%    
%                open_vbox d opens a new pretty-printing box  with offset d. 
%               This box is --vertical--: every break hint inside this  box
%               leads to a new line.  When a new line is printed in the box, d
%               is added to the  current indentation.
%  
%<<
%  val open_hvbox : int -> unit
%>>
%    
%                open_hvbox d opens a new pretty-printing box  with offset d. 
%               This box is --horizontal-vertical--: it behaves as an 
%               --horizontal-- box if it fits on a single line,  otherwise it
%               behaves as a --vertical-- box.  When a new line is printed in
%               the box, d is added to the  current indentation.
%  
%<<
%  val open_hovbox : int -> unit
%>>
%    
%                open_hovbox d opens a new pretty-printing box  with offset d. 
%               This box is --horizontal or vertical--: break hints  inside this
%               box may lead to a new line, if there is no more room  on the
%               line to print the remainder of the box.  When a new line is
%               printed in the box, d is added to the  current indentation.
%  
%
%Tabulations
%===========
%  
%<<
%  val open_tbox : unit -> unit
%>>
%    
%                Opens a tabulation box.
%  
%<<
%  val close_tbox : unit -> unit
%>>
%    
%                Closes the most recently opened tabulation box.
%  
%<<
%  val print_tbreak : int -> int -> unit
%>>
%    
%                Break hint in a tabulation box.  print_tbreak spaces offset
%               moves the insertion point to  the next tabulation (spaces being
%               added to this position).  Nothing occurs if insertion point is
%               already on a  tabulation mark.  If there is no next tabulation
%               on the line, then a newline  is printed and the insertion point
%               moves to the first  tabulation of the box.  If a new line is
%               printed, offset is added to the current  indentation.
%  
%<<
%  val set_tab : unit -> unit
%>>
%    
%                Sets a tabulation mark at the current insertion point.
%  
%<<
%  val print_tab : unit -> unit
%>>
%    
%                print_tab () is equivalent to print_tbreak (0,0).
%  
%
%Ellipsis
%========
%  
%<<
%  val set_ellipsis_text : string -> unit
%>>
%    
%                Set the text of the ellipsis printed when too many boxes  are
%               opened (a single dot, ., by default).
%  
%<<
%  val get_ellipsis_text : unit -> string
%>>
%    
%                Return the text of the ellipsis.
%  
%
%Tags
%====
%  
%<<
%  type tag = string 
%>>
%   
%  Tags are used to decorate printed entities for user-s defined  purposes, e.g.
%setting font and giving size indications for a  display device, or marking
%delimitations of semantics entities  (e.g. HTML or TeX elements or terminal
%escape sequences).
%  By default, those tags do not influence line breaking calculation:  the tag
%--markers-- are not considered as part of the printing  material that drives
%line breaking (in other words, the length of  those strings is considered as
%zero for line breaking).
%  Thus, tag handling is in some sense transparent to pretty-printing  and does
%not interfere with usual pretty-printing. Hence, a single  pretty printing
%routine can output both simple --verbatim--  material or richer decorated
%output depending on the treatment of  tags. By default, tags are not active,
%hence the output is not  decorated with tag information. Once set_tags is set
%to true,  the pretty printer engine honors tags and decorates the output 
%accordingly.
%  When a tag has been opened (or closed), it is both and successively 
%--printed-- and --marked--. Printing a tag means calling a  formatter specific
%function with the name of the tag as argument:  that --tag printing-- function
%can then print any regular material  to the formatter (so that this material is
%enqueued as usual in the  formatter queue for further line'breaking
%computation). Marking a  tag means to output an arbitrary string (the --tag
%marker--),  directly into the output device of the formatter. Hence, the 
%formatter specific --tag marking-- function must return the tag  marker string
%associated to its tag argument. Being flushed  directly into the output device
%of the formatter, tag marker  strings are not considered as part of the
%printing material that  drives line breaking (in other words, the length of the
%strings  corresponding to tag markers is considered as zero for line 
%breaking). In addition, advanced users may take advantage of  the specificity
%of tag markers to be precisely output when the  pretty printer has already
%decided where to break the lines, and  precisely when the queue is flushed into
%the output device.
%  In the spirit of HTML tags, the default tag marking functions  output tags
%enclosed in "<" and ">": hence, the opening marker of  tag t is "<t>" and the
%closing marker "</t>".
%  Default tag printing functions just do nothing.
%  Tag marking and tag printing functions are user definable and can  be set by
%calling set_formatter_tag_functions.
%<<
%  val open_tag : tag -> unit
%>>
%    
%                open_tag t opens the tag named t; the print_open_tag  function
%               of the formatter is called with t as argument;  the tag marker
%               mark_open_tag t will be flushed into the output  device of the
%               formatter.
%  
%<<
%  val close_tag : unit -> unit
%>>
%    
%                close_tag () closes the most recently opened tag t.  In
%               addition, the print_close_tag function of the formatter is
%               called  with t as argument. The marker mark_close_tag t will be
%               flushed  into the output device of the formatter.
%  
%<<
%  val set_tags : bool -> unit
%>>
%    
%                set_tags b turns on or off the treatment of tags (default is
%               off).
%  
%<<
%  val set_print_tags : bool -> unit
%>>
%   
%<<
%  val set_mark_tags : bool -> unit
%>>
%    
%                set_print_tags b turns on or off the printing of tags, while 
%               set_mark_tags b turns on or off the output of tag markers.
%  
%<<
%  val get_print_tags : unit -> bool
%>>
%   
%<<
%  val get_mark_tags : unit -> bool
%>>
%    
%                Return the current status of tags printing and tags marking.
%  
%
%Redirecting formatter output
%============================
%  
%<<
%  val set_formatter_out_channel : Pervasives.out_channel -> unit
%>>
%    
%                Redirect the pretty-printer output to the given channel.
%  
%<<
%  val set_formatter_output_functions :
%    (string -> int -> int -> unit) -> (unit -> unit) -> unit
%>>
%    
%                set_formatter_output_functions out flush redirects the 
%               pretty-printer output to the functions out and flush.
%               The out function performs the pretty-printer output. It is
%               called  with a string s, a start position p, and a number of
%               characters  n; it is supposed to output characters p to p + n -
%               1 of  s. The flush function is called whenever the
%               pretty-printer is  flushed using print_flush or print_newline.
%  
%<<
%  val get_formatter_output_functions :
%    unit -> (string -> int -> int -> unit) * (unit -> unit)
%>>
%    
%                Return the current output functions of the pretty-printer.
%  
%
%Changing the meaning of printing tags
%=====================================
%  
%<<
%  type formatter_tag_functions = {
%    mark_open_tag : tag -> string ;
%    mark_close_tag : tag -> string ;
%    print_open_tag : tag -> unit ;
%    print_close_tag : tag -> unit ;
%  }
%>>
%    
%                The tag handling functions specific to a formatter:  mark
%               versions are the --tag marking-- functions that associate a
%               string  marker to a tag in order for the pretty-printing engine
%               to flush  those markers as 0 length tokens in the output device
%               of the formatter.  print versions are the --tag printing--
%               functions that can perform  regular printing when a tag is
%               closed or opened.
%  
%<<
%  val set_formatter_tag_functions : formatter_tag_functions -> unit
%>>
%   
%  set_formatter_tag_functions tag_funs changes the meaning of  opening and
%closing tags to use the functions in tag_funs.
%  When opening a tag name t, the string t is passed to the  opening tag marking
%function (the mark_open_tag field of the  record tag_funs), that must return
%the opening tag marker for  that name. When the next call to close_tag ()
%happens, the tag  name t is sent back to the closing tag marking function (the 
%mark_close_tag field of record tag_funs), that must return a  closing tag
%marker for that name.
%  The print_ field of the record contains the functions that are  called at tag
%opening and tag closing time, to output regular  material in the pretty-printer
%queue.
%<<
%  val get_formatter_tag_functions : unit -> formatter_tag_functions
%>>
%    
%                Return the current tag functions of the pretty-printer.
%  
%
%Changing the meaning of pretty printing (indentation, line breaking, and
%========================================================================
%printing material)
%==================
%  
%<<
%  val set_all_formatter_output_functions :
%    out:(string -> int -> int -> unit) ->
%    flush:(unit -> unit) ->
%    newline:(unit -> unit) -> spaces:(int -> unit) -> unit
%>>
%    
%                set_all_formatter_output_functions out flush outnewline
%               outspace  redirects the pretty-printer output to the functions
%               out and  flush as described in set_formatter_output_functions.
%               In  addition, the pretty-printer function that outputs a newline
%               is set  to the function outnewline and the function that outputs
%                indentation spaces is set to the function outspace.
%               This way, you can change the meaning of indentation (which can
%               be  something else than just printing space characters) and the 
%               meaning of new lines opening (which can be connected to any
%               other  action needed by the application at hand). The two
%               functions  outspace and outnewline are normally connected to out
%               and  flush: respective default values for outspace and
%               outnewline  are out (String.make n - -) 0 n and out "\n" 0 1.
%  
%<<
%  val get_all_formatter_output_functions :
%    unit ->
%    (string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) *
%    (int -> unit)
%>>
%    
%                Return the current output functions of the pretty-printer, 
%               including line breaking and indentation functions.
%  
%
%Multiple formatted output
%=========================
%  
%<<
%  type formatter 
%>>
%    
%                Abstract data type corresponding to a pretty-printer (also
%               called a  formatter) and all its machinery.  Defining new
%               pretty-printers permits the output of  material in parallel on
%               several channels.  Parameters of a pretty-printer are local to
%               this pretty-printer:  margin, maximum indentation limit, maximum
%               number of boxes  simultaneously opened, ellipsis, and so on, are
%               specific to  each pretty-printer and may be fixed independently.
%                Given an output channel oc, a new formatter writing to  that
%               channel is obtained by calling formatter_of_out_channel oc. 
%               Alternatively, the make_formatter function allocates a new 
%               formatter with explicit output and flushing functions 
%               (convenient to output material to strings for instance).
%  
%<<
%  val formatter_of_out_channel : Pervasives.out_channel -> formatter
%>>
%    
%                formatter_of_out_channel oc returns a new formatter that 
%               writes to the corresponding channel oc.
%  
%<<
%  val std_formatter : formatter
%>>
%    
%                The standard formatter used by the formatting functions  above.
%               It is defined as formatter_of_out_channel stdout.
%  
%<<
%  val err_formatter : formatter
%>>
%    
%                A formatter to use with formatting functions below for  output
%               to standard error. It is defined as  formatter_of_out_channel
%               stderr.
%  
%<<
%  val formatter_of_buffer : Buffer.t -> formatter
%>>
%    
%                formatter_of_buffer b returns a new formatter writing to 
%               buffer b. As usual, the formatter has to be flushed at  the end
%               of pretty printing, using pp_print_flush or  pp_print_newline,
%               to display all the pending material.
%  
%<<
%  val stdbuf : Buffer.t
%>>
%    
%                The string buffer in which str_formatter writes.
%  
%<<
%  val str_formatter : formatter
%>>
%    
%                A formatter to use with formatting functions below for  output
%               to the stdbuf string buffer.  str_formatter is defined as
%               formatter_of_buffer stdbuf.
%  
%<<
%  val flush_str_formatter : unit -> string
%>>
%    
%                Returns the material printed with str_formatter, flushes  the
%               formatter and resets the corresponding buffer.
%  
%<<
%  val make_formatter :
%    (string -> int -> int -> unit) -> (unit -> unit) -> formatter
%>>
%    
%                make_formatter out flush returns a new formatter that  writes
%               according to the output function out, and the flushing  function
%               flush. Hence, a formatter to the out channel oc  is returned by
%               make_formatter (output oc) (fun () -> flush oc).
%  
%
%Basic functions to use with formatters
%======================================
%  
%<<
%  val pp_open_hbox : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_open_vbox : formatter -> int -> unit
%>>
%   
%<<
%  val pp_open_hvbox : formatter -> int -> unit
%>>
%   
%<<
%  val pp_open_hovbox : formatter -> int -> unit
%>>
%   
%<<
%  val pp_open_box : formatter -> int -> unit
%>>
%   
%<<
%  val pp_close_box : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_open_tag : formatter -> string -> unit
%>>
%   
%<<
%  val pp_close_tag : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_print_string : formatter -> string -> unit
%>>
%   
%<<
%  val pp_print_as : formatter -> int -> string -> unit
%>>
%   
%<<
%  val pp_print_int : formatter -> int -> unit
%>>
%   
%<<
%  val pp_print_float : formatter -> float -> unit
%>>
%   
%<<
%  val pp_print_char : formatter -> char -> unit
%>>
%   
%<<
%  val pp_print_bool : formatter -> bool -> unit
%>>
%   
%<<
%  val pp_print_break : formatter -> int -> int -> unit
%>>
%   
%<<
%  val pp_print_cut : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_print_space : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_force_newline : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_print_flush : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_print_newline : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_print_if_newline : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_open_tbox : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_close_tbox : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_print_tbreak : formatter -> int -> int -> unit
%>>
%   
%<<
%  val pp_set_tab : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_print_tab : formatter -> unit -> unit
%>>
%   
%<<
%  val pp_set_tags : formatter -> bool -> unit
%>>
%   
%<<
%  val pp_set_print_tags : formatter -> bool -> unit
%>>
%   
%<<
%  val pp_set_mark_tags : formatter -> bool -> unit
%>>
%   
%<<
%  val pp_get_print_tags : formatter -> unit -> bool
%>>
%   
%<<
%  val pp_get_mark_tags : formatter -> unit -> bool
%>>
%   
%<<
%  val pp_set_margin : formatter -> int -> unit
%>>
%   
%<<
%  val pp_get_margin : formatter -> unit -> int
%>>
%   
%<<
%  val pp_set_max_indent : formatter -> int -> unit
%>>
%   
%<<
%  val pp_get_max_indent : formatter -> unit -> int
%>>
%   
%<<
%  val pp_set_max_boxes : formatter -> int -> unit
%>>
%   
%<<
%  val pp_get_max_boxes : formatter -> unit -> int
%>>
%   
%<<
%  val pp_over_max_boxes : formatter -> unit -> bool
%>>
%   
%<<
%  val pp_set_ellipsis_text : formatter -> string -> unit
%>>
%   
%<<
%  val pp_get_ellipsis_text : formatter -> unit -> string
%>>
%   
%<<
%  val pp_set_formatter_out_channel :
%    formatter -> Pervasives.out_channel -> unit
%>>
%   
%<<
%  val pp_set_formatter_output_functions :
%    formatter -> (string -> int -> int -> unit) -> (unit -> unit) -> unit
%>>
%   
%<<
%  val pp_get_formatter_output_functions :
%    formatter -> unit -> (string -> int -> int -> unit) * (unit -> unit)
%>>
%   
%<<
%  val pp_set_all_formatter_output_functions :
%    formatter ->
%    out:(string -> int -> int -> unit) ->
%    flush:(unit -> unit) ->
%    newline:(unit -> unit) -> spaces:(int -> unit) -> unit
%>>
%   
%<<
%  val pp_get_all_formatter_output_functions :
%    formatter ->
%    unit ->
%    (string -> int -> int -> unit) * (unit -> unit) * (unit -> unit) *
%    (int -> unit)
%>>
%   
%<<
%  val pp_set_formatter_tag_functions :
%    formatter -> formatter_tag_functions -> unit
%>>
%   
%<<
%  val pp_get_formatter_tag_functions :
%    formatter -> unit -> formatter_tag_functions
%>>
%    
%                These functions are the basic ones: usual functions  operating
%               on the standard formatter are defined via partial  evaluation of
%               these primitives. For instance,  print_string is equal to
%               pp_print_string std_formatter.
%  
%
%printf like functions for pretty-printing.
%==========================================
%  
%<<
%  val fprintf : formatter -> ('a, formatter, unit) Pervasives.format -> 'a
%>>
%    
%                fprintf ff format arg1 ... argN formats the arguments  arg1 to
%               argN according to the format string format,  and outputs the
%               resulting string on the formatter ff.  The format is a character
%               string which contains three types of  objects: plain characters
%               and conversion specifications as  specified in the printf
%               module, and pretty-printing  indications.  The pretty-printing
%               indication characters are introduced by  a @ character, and
%               their meanings are:
%                 
%                - @[: open a pretty-printing box. The type and offset of the 
%                  box may be optionally specified with the following syntax: 
%                  the < character, followed by an optional box type indication,
%                   then an optional integer offset, and the closing >
%                  character.  Box type is one of h, v, hv, b, or hov,  which
%                  stand respectively for an horizontal box, a vertical box,  an
%                  --horizontal-vertical-- box, or an --horizontal or 
%                  vertical-- box (b standing for an --horizontal or  vertical--
%                  box demonstrating indentation and hov standing  for a
%                  regular--horizontal or vertical-- box).  For instance, @[<hov
%                  2> opens an --horizontal or vertical--  box with indentation
%                  2 as obtained with open_hovbox 2.  For more details about
%                  boxes, see the various box opening  functions open_*box. 
%                - @]: close the most recently opened pretty-printing box. 
%                - @,: output a good break as with print_cut (). 
%                - @ : output a space, as with print_space (). 
%                - @\n: force a newline, as with force_newline (). 
%                - @;: output a good break as with print_break. The  nspaces and
%                  offset parameters of the break may be  optionally specified
%                  with the following syntax:  the < character, followed by an
%                  integer nspaces value,  then an integer offset, and a closing
%                  > character.  If no parameters are provided, the good break
%                  defaults to a  space. 
%                - @?: flush the pretty printer as with print_flush ().  This is
%                  equivalent to the conversion %!. 
%                - @.: flush the pretty printer and output a new line, as with 
%                  print_newline (). 
%                - @<n>: print the following item as if it were of length n. 
%                  Hence, printf "@<0>%s" arg is equivalent to print_as 0 arg. 
%                  If @<n> is not followed by a conversion specification,  then
%                  the following character of the format is printed as if  it
%                  were of length n. 
%                - @{: open a tag. The name of the tag may be optionally 
%                  specified with the following syntax:  the < character,
%                  followed by an optional string  specification, and the
%                  closing > character. The string  specification is any
%                  character string that does not contain the  closing character
%                  ->-. If omitted, the tag name defaults to the  empty string. 
%                  For more details about tags, see the functions open_tag and 
%                  close_tag. 
%                - @}: close the most recently opened tag. 
%                - @@: print a plain @ character. 
%               
%               Example: printf "@[%s@ %d@]" "x =" 1 is equivalent to  open_box
%               (); print_string "x ="; print_space (); print_int 1; close_box
%               ().  It prints x = 1 within a pretty-printing box.
%  
%<<
%  val printf : ('a, formatter, unit) Pervasives.format -> 'a
%>>
%    
%                Same as fprintf above, but output on std_formatter.
%  
%<<
%  val eprintf : ('a, formatter, unit) Pervasives.format -> 'a
%>>
%    
%                Same as fprintf above, but output on err_formatter.
%  
%<<
%  val sprintf : ('a, unit, string) Pervasives.format -> 'a
%>>
%    
%                Same as printf above, but instead of printing on a formatter, 
%               returns a string containing the result of formatting the
%               arguments.  Note that the pretty-printer queue is flushed at the
%               end of each  call to sprintf.
%               In case of multiple and related calls to sprintf to output 
%               material on a single string, you should consider using fprintf 
%               with a formatter writing to a buffer: flushing the buffer at the
%                end of pretty-printing returns the desired string. You can also
%               use  the predefined formatter str_formatter and call 
%               flush_str_formatter () to get the result.
%  
%<<
%  val bprintf : Buffer.t -> ('a, formatter, unit) Pervasives.format -> 'a
%>>
%    
%                Same as sprintf above, but instead of printing on a string, 
%               writes into the given extensible buffer.  As for sprintf, the
%               pretty-printer queue is flushed at the end of each  call to
%               bprintf.
%               In case of multiple and related calls to bprintf to output 
%               material on the same buffer b, you should consider using 
%               fprintf with a formatter writing to the buffer b (as obtained 
%               by formatter_of_buffer b), otherwise the repeated flushes of the
%                pretty-printer queue would result in unexpected and badly
%               formatted  output.
%  
%<<
%  val kfprintf :
%    (formatter -> 'a) ->
%    formatter -> ('b, formatter, unit, 'a) format4 -> 'b
%>>
%    
%                Same as fprintf above, but instead of returning immediately, 
%               passes the formatter to its first argument at the end of
%               printing.
%  
%<<
%  val ksprintf : (string -> 'a) -> ('b, unit, string, 'a) format4 -> 'b
%>>
%    
%                Same as sprintf above, but instead of returning the string, 
%               passes it to the first argument.
%  
%<<
%  val kprintf : (string -> 'a) -> ('b, unit, string, 'a) format4 -> 'b
%>>
%    
%                A deprecated synonym for ksprintf.
%  
%
%
%20.10  Module Gc : Memory management control and statistics; finalised values.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  type stat = {
%    minor_words : float ;
%>>
%   
%                Number of words allocated in the minor heap since  the program
%               was started. This number is accurate in  byte'code programs, but
%               only an approximation in programs  compiled to native code. 
%   
%<<
%    promoted_words : float ;
%>>
%   
%                Number of words allocated in the minor heap that  survived a
%               minor collection and were moved to the major heap  since the
%               program was started. 
%   
%<<
%    major_words : float ;
%>>
%   
%                Number of words allocated in the major heap, including  the
%               promoted words, since the program was started. 
%   
%<<
%    minor_collections : int ;
%>>
%   
%                Number of minor collections since the program was started. 
%   
%<<
%    major_collections : int ;
%>>
%   
%                Number of major collection cycles completed since the program 
%               was started. 
%   
%<<
%    heap_words : int ;
%>>
%   
%                Total size of the major heap, in words. 
%   
%<<
%    heap_chunks : int ;
%>>
%   
%                Number of contiguous pieces of memory that make up the major
%               heap. 
%   
%<<
%    live_words : int ;
%>>
%   
%                Number of words of live data in the major heap, including the
%               header  words. 
%   
%<<
%    live_blocks : int ;
%>>
%   
%                Number of live blocks in the major heap. 
%   
%<<
%    free_words : int ;
%>>
%   
%                Number of words in the free list. 
%   
%<<
%    free_blocks : int ;
%>>
%   
%                Number of blocks in the free list. 
%   
%<<
%    largest_free : int ;
%>>
%   
%                Size (in words) of the largest block in the free list. 
%   
%<<
%    fragments : int ;
%>>
%   
%                Number of wasted words due to fragmentation. These are  1-words
%               free blocks placed between two live blocks. They  are not
%               available for allocation. 
%   
%<<
%    compactions : int ;
%>>
%   
%                Number of heap compactions since the program was started. 
%   
%<<
%    top_heap_words : int ;
%>>
%   
%                Maximum size reached by the major heap, in words. 
%   
%<<
%  }
%>>
%    
%                The memory management counters are returned in a stat record.
%               The total amount of memory allocated by the program since it was
%               started  is (in words) minor_words + major_words -
%               promoted_words. Multiply by  the word size (4 on a 32'bit
%               machine, 8 on a 64'bit machine) to get  the number of bytes.
%  
%<<
%  type control = {
%    mutable minor_heap_size : int ;
%>>
%   
%                The size (in words) of the minor heap. Changing  this parameter
%               will trigger a minor collection. Default: 32k. 
%   
%<<
%    mutable major_heap_increment : int ;
%>>
%   
%                The minimum number of words to add to the  major heap when
%               increasing it. Default: 62k. 
%   
%<<
%    mutable space_overhead : int ;
%>>
%   
%                The major GC speed is computed from this parameter.  This is
%               the memory that will be "wasted" because the GC does not 
%               immediatly collect unreachable blocks. It is expressed as a 
%               percentage of the memory used for live data.  The GC will work
%               more (use more CPU time and collect  blocks more eagerly) if
%               space_overhead is smaller.  Default: 80. 
%   
%<<
%    mutable verbose : int ;
%>>
%   
%                This value controls the GC messages on standard error output. 
%               It is a sum of some of the following flags, to print messages 
%               on the corresponding events:
%                 
%                - 0x001 Start of major GC cycle. 
%                - 0x002 Minor collection and major GC slice. 
%                - 0x004 Growing and shrinking of the heap. 
%                - 0x008 Resizing of stacks and memory manager tables. 
%                - 0x010 Heap compaction. 
%                - 0x020 Change of GC parameters. 
%                - 0x040 Computation of major GC slice size. 
%                - 0x080 Calling of finalisation functions. 
%                - 0x100 Bytecode executable search at start-up. 
%                - 0x200 Computation of compaction triggering condition. 
%                  Default: 0. 
%  
%   
%<<
%    mutable max_overhead : int ;
%>>
%   
%                Heap compaction is triggered when the estimated amount  of
%               "wasted" memory is more than max_overhead percent of the  amount
%               of live data. If max_overhead is set to 0, heap  compaction is
%               triggered at the end of each major GC cycle  (this setting is
%               intended for testing purposes only).  If max_overhead >=
%               1000000, compaction is never triggered.  Default: 500. 
%   
%<<
%    mutable stack_limit : int ;
%>>
%   
%                The maximum size of the stack (in words). This is only 
%               relevant to the byte'code runtime, as the native code runtime 
%               uses the operating system-s stack. Default: 256k. 
%   
%<<
%  }
%>>
%    
%                The GC parameters are given as a control record.
%  
%<<
%  val stat : unit -> stat
%>>
%    
%                Return the current values of the memory management counters in
%               a  stat record. This function examines every heap block to get
%               the  statistics.
%  
%<<
%  val quick_stat : unit -> stat
%>>
%    
%                Same as stat except that live_words, live_blocks, free_words, 
%               free_blocks, largest_free, and fragments are set to 0. This 
%               function is much faster than stat because it does not need to go
%                through the heap.
%  
%<<
%  val counters : unit -> float * float * float
%>>
%    
%                Return (minor_words, promoted_words, major_words). This
%               function  is as fast at quick_stat.
%  
%<<
%  val get : unit -> control
%>>
%    
%                Return the current values of the GC parameters in a control
%               record.
%  
%<<
%  val set : control -> unit
%>>
%    
%                set r changes the GC parameters according to the control record
%               r.  The normal usage is: Gc.set { (Gc.get()) with Gc.verbose =
%               0x00d }
%  
%<<
%  val minor : unit -> unit
%>>
%    
%                Trigger a minor collection.
%  
%<<
%  val major_slice : int -> int
%>>
%    
%                Do a minor collection and a slice of major collection. The
%               argument  is the size of the slice, 0 to use the
%               automatically'computed  slice size. In all cases, the result is
%               the computed slice size.
%  
%<<
%  val major : unit -> unit
%>>
%    
%                Do a minor collection and finish the current major collection
%               cycle.
%  
%<<
%  val full_major : unit -> unit
%>>
%    
%                Do a minor collection, finish the current major collection
%               cycle,  and perform a complete new cycle. This will collect all
%               currently  unreachable blocks.
%  
%<<
%  val compact : unit -> unit
%>>
%    
%                Perform a full major collection and compact the heap. Note that
%               heap  compaction is a lengthy operation.
%  
%<<
%  val print_stat : Pervasives.out_channel -> unit
%>>
%    
%                Print the current values of the memory management counters (in 
%               human-readable form) into the channel argument.
%  
%<<
%  val allocated_bytes : unit -> float
%>>
%    
%                Return the total number of bytes allocated since the program
%               was  started. It is returned as a float to avoid overflow
%               problems  with int on 32'bit machines.
%  
%<<
%  val finalise : ('a -> unit) -> 'a -> unit
%>>
%    
%                finalise f v registers f as a finalisation function for v.  v
%               must be heap'allocated. f will be called with v as  argument at
%               some point between the first time v becomes unreachable  and the
%               time v is collected by the GC. Several functions can  be
%               registered for the same value, or even several instances of the 
%               same function. Each instance will be called once (or never,  if
%               the program terminates before v becomes unreachable).
%               The GC will call the finalisation functions in the order of 
%               deallocation. When several values become unreachable at the 
%               same time (i.e. during the same GC cycle), the finalisation 
%               functions will be called in the reverse order of the
%               corresponding  calls to finalise. If finalise is called in the
%               same order  as the values are allocated, that means each value
%               is finalised  before the values it depends upon. Of course, this
%               becomes  false if additional dependencies are introduced by
%               assignments.
%               Anything reachable from the closure of finalisation functions 
%               is considered reachable, so the following code will not work  as
%               expected:
%                 
%                -  let v = ... in Gc.finalise (fun x -> ...) v  
%               
%               Instead you should write:
%                 
%                -  let f = fun x -> ... ;; let v = ... in Gc.finalise f v  
%               
%               The f function can use all features of O'caml, including 
%               assignments that make the value reachable again. It can also 
%               loop forever (in this case, the other  finalisation functions
%               will be called during the execution of f).  It can call finalise
%               on v or other values to register other  functions or even
%               itself. It can raise an exception; in this case  the exception
%               will interrupt whatever the program was doing when  the function
%               was called.
%               finalise will raise Invalid_argument if v is not 
%               heap'allocated. Some examples of values that are not 
%               heap'allocated are integers, constant constructors, booleans, 
%               the empty array, the empty list, the unit value. The exact list 
%               of what is heap'allocated or not is implementation-dependent. 
%               Some constant values can be heap'allocated but never deallocated
%                during the lifetime of the program, for example a list of
%               integer  constants; this is also implementation-dependent.  You
%               should also be aware that compiler optimisations may duplicate 
%               some immutable values, for example floating-point numbers when 
%               stored into arrays, so they can be finalised and collected while
%                another copy is still in use by the program.
%               The results of calling String.make[20.33], String.create[20.33],
%                Array.make[20.2], and Pervasives.ref[19.2] are guaranteed to be
%                heap'allocated and non'constant except when the length argument
%               is 0.
%  
%<<
%  val finalise_release : unit -> unit
%>>
%    
%                A finalisation function may call finalise_release to tell the 
%               GC that it can launch the next finalisation function without
%               waiting  for the current one to return.
%  
%<<
%  type alarm 
%>>
%    
%                An alarm is a piece of data that calls a user function at the
%               end of  each major GC cycle. The following functions are
%               provided to create  and delete alarms.
%  
%<<
%  val create_alarm : (unit -> unit) -> alarm
%>>
%    
%                create_alarm f will arrange for f to be called at the end of
%               each  major GC cycle, starting with the current cycle or the
%               next one.  A value of type alarm is returned that you can  use
%               to call delete_alarm.
%  
%<<
%  val delete_alarm : alarm -> unit
%>>
%    
%                delete_alarm a will stop the calls to the function associated 
%               to a. Calling delete_alarm a again has no effect.
%  
%
%
%20.11  Module Genlex : A generic lexical analyzer.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module implements a simple --standard-- lexical analyzer, presented  as
%a function from character streams to token streams. It implements  roughly the
%lexical conventions of Caml, but is parameterized by the  set of keywords of
%your language. 
%  Example: a lexer suitable for a desk calculator is obtained by  
%<<
%       let lexer = make_lexer ["+";"-";"*";"/";"let";"="; "("; ")"]  
%>>
%  
%  The associated parser would be a function from token stream  to, for
%instance, int, and would have rules such as:
%<<
%  
%             let parse_expr = parser
%                    [< -Int n >] -> n
%                  | [< -Kwd "("; n = parse_expr; -Kwd ")" >] -> n
%                  | [< n1 = parse_expr; n2 = parse_remainder n1 >] -> n2
%             and parse_remainder n1 = parser
%                    [< -Kwd "+"; n2 = parse_expr >] -> n1+n2
%                  | ...
%     
%>>
%  
%  0.5cm
%<<
%  type token =
%    | Kwd of string
%    | Ident of string
%    | Int of int
%    | Float of float
%    | String of string
%    | Char of char
%>>
%    
%                The type of tokens. The lexical classes are: Int and Float  for
%               integer and floating-point numbers; String for  string literals,
%               enclosed in double quotes; Char for  character literals,
%               enclosed in single quotes; Ident for  identifiers (either
%               sequences of letters, digits, underscores  and quotes, or
%               sequences of --operator characters-- such as  +, *, etc); and
%               Kwd for keywords (either identifiers or  single --special
%               characters-- such as (, }, etc).
%  
%<<
%  val make_lexer : string list -> char Stream.t -> token Stream.t
%>>
%    
%                Construct the lexer function. The first argument is the list of
%                keywords. An identifier s is returned as Kwd s if s  belongs to
%               this list, and as Ident s otherwise.  A special character s is
%               returned as Kwd s if s  belongs to this list, and cause a
%               lexical error (exception  Parse_error) otherwise. Blanks and
%               newlines are skipped.  Comments delimited by (* and *) are
%               skipped as well,  and can be nested.
%  
%
%
%20.12  Module Hashtbl : Hash tables and hash functions.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  Hash tables are hashed association tables, with in-place modification.
%  0.5cm
%
%Generic interface
%=================
%  
%<<
%  type ('a, 'b) t 
%>>
%    
%                The type of hash tables from type 'a to type 'b.
%  
%<<
%  val create : int -> ('a, 'b) t
%>>
%    
%                Hashtbl.create n creates a new, empty hash table, with  initial
%               size n. For best results, n should be on the  order of the
%               expected number of elements that will be in  the table. The
%               table grows as needed, so n is just an  initial guess.
%  
%<<
%  val clear : ('a, 'b) t -> unit
%>>
%    
%                Empty a hash table.
%  
%<<
%  val add : ('a, 'b) t -> 'a -> 'b -> unit
%>>
%    
%                Hashtbl.add tbl x y adds a binding of x to y in table tbl. 
%               Previous bindings for x are not removed, but simply  hidden.
%               That is, after performing Hashtbl.remove[20.12] tbl x,  the
%               previous binding for x, if any, is restored.  (Same behavior as
%               with association lists.)
%  
%<<
%  val copy : ('a, 'b) t -> ('a, 'b) t
%>>
%    
%                Return a copy of the given hashtable.
%  
%<<
%  val find : ('a, 'b) t -> 'a -> 'b
%>>
%    
%                Hashtbl.find tbl x returns the current binding of x in tbl,  or
%               raises Not_found if no such binding exists.
%  
%<<
%  val find_all : ('a, 'b) t -> 'a -> 'b list
%>>
%    
%                Hashtbl.find_all tbl x returns the list of all data  associated
%               with x in tbl.  The current binding is returned first, then the
%               previous  bindings, in reverse order of introduction in the
%               table.
%  
%<<
%  val mem : ('a, 'b) t -> 'a -> bool
%>>
%    
%                Hashtbl.mem tbl x checks if x is bound in tbl.
%  
%<<
%  val remove : ('a, 'b) t -> 'a -> unit
%>>
%    
%                Hashtbl.remove tbl x removes the current binding of x in tbl, 
%               restoring the previous binding if it exists.  It does nothing if
%               x is not bound in tbl.
%  
%<<
%  val replace : ('a, 'b) t -> 'a -> 'b -> unit
%>>
%    
%                Hashtbl.replace tbl x y replaces the current binding of x  in
%               tbl by a binding of x to y. If x is unbound in tbl,  a binding
%               of x to y is added to tbl.  This is functionally equivalent to
%               Hashtbl.remove[20.12] tbl x  followed by Hashtbl.add[20.12] tbl
%               x y.
%  
%<<
%  val iter : ('a -> 'b -> unit) -> ('a, 'b) t -> unit
%>>
%    
%                Hashtbl.iter f tbl applies f to all bindings in table tbl.  f
%               receives the key as first argument, and the associated value  as
%               second argument. Each binding is presented exactly once to f. 
%               The order in which the bindings are passed to f is unspecified. 
%               However, if the table contains several bindings for the same
%               key,  they are passed to f in reverse order of introduction,
%               that is,  the most recent binding is passed first.
%  
%<<
%  val fold : ('a -> 'b -> 'c -> 'c) -> ('a, 'b) t -> 'c -> 'c
%>>
%    
%                Hashtbl.fold f tbl init computes  (f kN dN ... (f k1 d1
%               init)...),  where k1 ... kN are the keys of all bindings in tbl,
%                and d1 ... dN are the associated values.  Each binding is
%               presented exactly once to f.  The order in which the bindings
%               are passed to f is unspecified.  However, if the table contains
%               several bindings for the same key,  they are passed to f in
%               reverse order of introduction, that is,  the most recent binding
%               is passed first.
%  
%<<
%  val length : ('a, 'b) t -> int
%>>
%    
%                Hashtbl.length tbl returns the number of bindings in tbl. 
%               Multiple bindings are counted multiply, so Hashtbl.length  gives
%               the number of times Hashtbl.iter calls its first argument.
%  
%
%Functorial interface
%====================
%  
%<<
%  module type HashedType = >>
%   
%    sig
% 
%  
%   <<
%     type t 
%   >>
%   
%                   The type of the hashtable keys.
% 
%   <<
%     val equal : t -> t -> bool
%   >>
%   
%                   The equality predicate used to compare keys.
% 
%   <<
%     val hash : t -> int
%   >>
%   
%                   A hashing function on keys. It must be such that if two keys
%                  are  equal according to equal, then they have identical hash
%                  values  as computed by hash.  Examples: suitable (equal,
%                  hash) pairs for arbitrary key  types include  ((=),
%                  Hashtbl.hash[20.12]) for comparing objects by structure, 
%                  ((fun x y -> compare x y = 0), Hashtbl.hash[20.12])  for
%                  comparing objects by structure and handling
%                  Pervasives.nan[19.2]  correctly, and  ((==),
%                  Hashtbl.hash[20.12]) for comparing objects by addresses 
%                  (e.g. for cyclic keys).
% 
%  
%  -  end
%  
%                The input signature of the functor Hashtbl.Make[20.12].
%  
%<<
%  module type S = >>
%   
%    sig
% 
%  
%   <<
%     type key 
%   >>
%  
%   <<
%     type 'a t 
%   >>
%  
%   <<
%     val create : int -> 'a t
%   >>
%  
%   <<
%     val clear : 'a t -> unit
%   >>
%  
%   <<
%     val copy : 'a t -> 'a t
%   >>
%  
%   <<
%     val add : 'a t -> key -> 'a -> unit
%   >>
%  
%   <<
%     val remove : 'a t -> key -> unit
%   >>
%  
%   <<
%     val find : 'a t -> key -> 'a
%   >>
%  
%   <<
%     val find_all : 'a t -> key -> 'a list
%   >>
%  
%   <<
%     val replace : 'a t -> key -> 'a -> unit
%   >>
%  
%   <<
%     val mem : 'a t -> key -> bool
%   >>
%  
%   <<
%     val iter : (key -> 'a -> unit) -> 'a t -> unit
%   >>
%  
%   <<
%     val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
%   >>
%  
%   <<
%     val length : 'a t -> int
%   >>
%   
%  -  end
%  
%                The output signature of the functor Hashtbl.Make[20.12].
%  
%<<
%  module Make : >>
%   
%  functor (H : HashedType) -> S  with type key = H.t
%                Functor building an implementation of the hashtable structure. 
%               The functor Hashtbl.Make returns a structure containing  a type
%               key of keys and a type 'a t of hash tables  associating data of
%               type 'a to keys of type key.  The operations perform similarly
%               to those of the generic  interface, but use the hashing and
%               equality functions  specified in the functor argument H instead
%               of generic  equality and hashing.
%  
%
%The polymorphic hash primitive
%==============================
%  
%<<
%  val hash : 'a -> int
%>>
%    
%                Hashtbl.hash x associates a positive integer to any value of 
%               any type. It is guaranteed that  if x = y or Pervasives.compare
%               x y = 0, then hash x = hash y.  Moreover, hash always
%               terminates, even on cyclic  structures.
%  
%<<
%  val hash_param : int -> int -> 'a -> int
%>>
%    
%                Hashtbl.hash_param n m x computes a hash value for x, with the 
%               same properties as for hash. The two extra parameters n and  m
%               give more precise control over hashing. Hashing performs a 
%               depth-first, right-to-left traversal of the structure x,
%               stopping  after n meaningful nodes were encountered, or m nodes,
%                meaningful or not, were encountered. Meaningful nodes are:
%               integers;  floating-point numbers; strings; characters;
%               booleans; and constant  constructors. Larger values of m and n
%               means that more  nodes are taken into account to compute the
%               final hash  value, and therefore collisions are less likely to
%               happen.  However, hashing takes longer. The parameters m and n 
%               govern the tradeoff between accuracy and speed.
%  
%
%
%20.13  Module Int32 : 32'bit integers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module provides operations on the type int32  of signed 32'bit integers.
%Unlike the built-in int type,  the type int32 is guaranteed to be exactly
%32'bit wide on all  platforms. All arithmetic operations over int32 are taken 
%modulo 2^32.
%  Performance notice: values of type int32 occupy more memory  space than
%values of type int, and arithmetic operations on  int32 are generally slower
%than those on int. Use int32  only when the application requires exact 32'bit
%arithmetic.
%  0.5cm
%<<
%  val zero : int32
%>>
%    
%                The 32'bit integer 0.
%  
%<<
%  val one : int32
%>>
%    
%                The 32'bit integer 1.
%  
%<<
%  val minus_one : int32
%>>
%    
%                The 32'bit integer -1.
%  
%<<
%  val neg : int32 -> int32
%>>
%    
%                Unary negation.
%  
%<<
%  val add : int32 -> int32 -> int32
%>>
%    
%                Addition.
%  
%<<
%  val sub : int32 -> int32 -> int32
%>>
%    
%                Subtraction.
%  
%<<
%  val mul : int32 -> int32 -> int32
%>>
%    
%                Multiplication.
%  
%<<
%  val div : int32 -> int32 -> int32
%>>
%    
%                Integer division. Raise Division_by_zero if the second 
%               argument is zero. This division rounds the real quotient of  its
%               arguments towards zero, as specified for Pervasives.(/)[19.2].
%  
%<<
%  val rem : int32 -> int32 -> int32
%>>
%    
%                Integer remainder. If y is not zero, the result  of Int32.rem x
%               y satisfies the following property:  x = Int32.add (Int32.mul
%               (Int32.div x y) y) (Int32.rem x y).  If y = 0, Int32.rem x y
%               raises Division_by_zero.
%  
%<<
%  val succ : int32 -> int32
%>>
%    
%                Successor. Int32.succ x is Int32.add x Int32.one.
%  
%<<
%  val pred : int32 -> int32
%>>
%    
%                Predecessor. Int32.pred x is Int32.sub x Int32.one.
%  
%<<
%  val abs : int32 -> int32
%>>
%    
%                Return the absolute value of its argument.
%  
%<<
%  val max_int : int32
%>>
%    
%                The greatest representable 32'bit integer, 2^31 - 1.
%  
%<<
%  val min_int : int32
%>>
%    
%                The smallest representable 32'bit integer, -2^31.
%  
%<<
%  val logand : int32 -> int32 -> int32
%>>
%    
%                Bitwise logical and.
%  
%<<
%  val logor : int32 -> int32 -> int32
%>>
%    
%                Bitwise logical or.
%  
%<<
%  val logxor : int32 -> int32 -> int32
%>>
%    
%                Bitwise logical exclusive or.
%  
%<<
%  val lognot : int32 -> int32
%>>
%    
%                Bitwise logical negation
%  
%<<
%  val shift_left : int32 -> int -> int32
%>>
%    
%                Int32.shift_left x y shifts x to the left by y bits.  The
%               result is unspecified if y < 0 or y >= 32.
%  
%<<
%  val shift_right : int32 -> int -> int32
%>>
%    
%                Int32.shift_right x y shifts x to the right by y bits.  This is
%               an arithmetic shift: the sign bit of x is replicated  and
%               inserted in the vacated bits.  The result is unspecified if y <
%               0 or y >= 32.
%  
%<<
%  val shift_right_logical : int32 -> int -> int32
%>>
%    
%                Int32.shift_right_logical x y shifts x to the right by y bits. 
%               This is a logical shift: zeroes are inserted in the vacated bits
%                regardless of the sign of x.  The result is unspecified if y <
%               0 or y >= 32.
%  
%<<
%  val of_int : int -> int32
%>>
%    
%                Convert the given integer (type int) to a 32'bit integer  (type
%               int32).
%  
%<<
%  val to_int : int32 -> int
%>>
%    
%                Convert the given 32'bit integer (type int32) to an  integer
%               (type int). On 32'bit platforms, the 32'bit integer  is taken
%               modulo 2^31, i.e. the high-order bit is lost  during the
%               conversion. On 64'bit platforms, the conversion  is exact.
%  
%<<
%  val of_float : float -> int32
%>>
%    
%                Convert the given floating-point number to a 32'bit integer, 
%               discarding the fractional part (truncate towards 0).  The result
%               of the conversion is undefined if, after truncation,  the number
%               is outside the range [Int32.min_int[20.13],
%               Int32.max_int[20.13]].
%  
%<<
%  val to_float : int32 -> float
%>>
%    
%                Convert the given 32'bit integer to a floating-point number.
%  
%<<
%  val of_string : string -> int32
%>>
%    
%                Convert the given string to a 32'bit integer.  The string is
%               read in decimal (by default) or in hexadecimal,  octal or binary
%               if the string begins with 0x, 0o or 0b  respectively.  Raise
%               Failure "int_of_string" if the given string is not  a valid
%               representation of an integer, or if the integer represented 
%               exceeds the range of integers representable in type int32.
%  
%<<
%  val to_string : int32 -> string
%>>
%    
%                Return the string representation of its argument, in signed
%               decimal.
%  
%<<
%  val bits_of_float : float -> int32
%>>
%    
%                Return the internal representation of the given float according
%                to the IEEE 754 floating-point --single format-- bit layout. 
%               Bit 31 of the result represents the sign of the float;  bits 30
%               to 23 represent the (biased) exponent; bits 22 to 0  represent
%               the mantissa.
%  
%<<
%  val float_of_bits : int32 -> float
%>>
%    
%                Return the floating-point number whose internal representation,
%                according to the IEEE 754 floating-point --single format-- bit
%               layout,  is the given int32.
%  
%<<
%  type t = int32 
%>>
%    
%                An alias for the type of 32'bit integers.
%  
%<<
%  val compare : t -> t -> int
%>>
%    
%                The comparison function for 32'bit integers, with the same
%               specification as  Pervasives.compare[19.2]. Along with the type
%               t, this function compare  allows the module Int32 to be passed
%               as argument to the functors  Set.Make[20.28] and
%               Map.Make[20.18].
%  
%
%
%20.14  Module Int64 : 64'bit integers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module provides operations on the type int64 of  signed 64'bit integers.
%Unlike the built-in int type,  the type int64 is guaranteed to be exactly
%64'bit wide on all  platforms. All arithmetic operations over int64 are taken 
%modulo 2^64
%  Performance notice: values of type int64 occupy more memory  space than
%values of type int, and arithmetic operations on  int64 are generally slower
%than those on int. Use int64  only when the application requires exact 64'bit
%arithmetic.
%  0.5cm
%<<
%  val zero : int64
%>>
%    
%                The 64'bit integer 0.
%  
%<<
%  val one : int64
%>>
%    
%                The 64'bit integer 1.
%  
%<<
%  val minus_one : int64
%>>
%    
%                The 64'bit integer -1.
%  
%<<
%  val neg : int64 -> int64
%>>
%    
%                Unary negation.
%  
%<<
%  val add : int64 -> int64 -> int64
%>>
%    
%                Addition.
%  
%<<
%  val sub : int64 -> int64 -> int64
%>>
%    
%                Subtraction.
%  
%<<
%  val mul : int64 -> int64 -> int64
%>>
%    
%                Multiplication.
%  
%<<
%  val div : int64 -> int64 -> int64
%>>
%    
%                Integer division. Raise Division_by_zero if the second 
%               argument is zero. This division rounds the real quotient of  its
%               arguments towards zero, as specified for Pervasives.(/)[19.2].
%  
%<<
%  val rem : int64 -> int64 -> int64
%>>
%    
%                Integer remainder. If y is not zero, the result  of Int64.rem x
%               y satisfies the following property:  x = Int64.add (Int64.mul
%               (Int64.div x y) y) (Int64.rem x y).  If y = 0, Int64.rem x y
%               raises Division_by_zero.
%  
%<<
%  val succ : int64 -> int64
%>>
%    
%                Successor. Int64.succ x is Int64.add x Int64.one.
%  
%<<
%  val pred : int64 -> int64
%>>
%    
%                Predecessor. Int64.pred x is Int64.sub x Int64.one.
%  
%<<
%  val abs : int64 -> int64
%>>
%    
%                Return the absolute value of its argument.
%  
%<<
%  val max_int : int64
%>>
%    
%                The greatest representable 64'bit integer, 2^63 - 1.
%  
%<<
%  val min_int : int64
%>>
%    
%                The smallest representable 64'bit integer, -2^63.
%  
%<<
%  val logand : int64 -> int64 -> int64
%>>
%    
%                Bitwise logical and.
%  
%<<
%  val logor : int64 -> int64 -> int64
%>>
%    
%                Bitwise logical or.
%  
%<<
%  val logxor : int64 -> int64 -> int64
%>>
%    
%                Bitwise logical exclusive or.
%  
%<<
%  val lognot : int64 -> int64
%>>
%    
%                Bitwise logical negation
%  
%<<
%  val shift_left : int64 -> int -> int64
%>>
%    
%                Int64.shift_left x y shifts x to the left by y bits.  The
%               result is unspecified if y < 0 or y >= 64.
%  
%<<
%  val shift_right : int64 -> int -> int64
%>>
%    
%                Int64.shift_right x y shifts x to the right by y bits.  This is
%               an arithmetic shift: the sign bit of x is replicated  and
%               inserted in the vacated bits.  The result is unspecified if y <
%               0 or y >= 64.
%  
%<<
%  val shift_right_logical : int64 -> int -> int64
%>>
%    
%                Int64.shift_right_logical x y shifts x to the right by y bits. 
%               This is a logical shift: zeroes are inserted in the vacated bits
%                regardless of the sign of x.  The result is unspecified if y <
%               0 or y >= 64.
%  
%<<
%  val of_int : int -> int64
%>>
%    
%                Convert the given integer (type int) to a 64'bit integer  (type
%               int64).
%  
%<<
%  val to_int : int64 -> int
%>>
%    
%                Convert the given 64'bit integer (type int64) to an  integer
%               (type int). On 64'bit platforms, the 64'bit integer  is taken
%               modulo 2^63, i.e. the high-order bit is lost  during the
%               conversion. On 32'bit platforms, the 64'bit integer  is taken
%               modulo 2^31, i.e. the top 33 bits are lost  during the
%               conversion.
%  
%<<
%  val of_float : float -> int64
%>>
%    
%                Convert the given floating-point number to a 64'bit integer, 
%               discarding the fractional part (truncate towards 0).  The result
%               of the conversion is undefined if, after truncation,  the number
%               is outside the range [Int64.min_int[20.14],
%               Int64.max_int[20.14]].
%  
%<<
%  val to_float : int64 -> float
%>>
%    
%                Convert the given 64'bit integer to a floating-point number.
%  
%<<
%  val of_int32 : int32 -> int64
%>>
%    
%                Convert the given 32'bit integer (type int32)  to a 64'bit
%               integer (type int64).
%  
%<<
%  val to_int32 : int64 -> int32
%>>
%    
%                Convert the given 64'bit integer (type int64) to a  32'bit
%               integer (type int32). The 64'bit integer  is taken modulo 2^32,
%               i.e. the top 32 bits are lost  during the conversion.
%  
%<<
%  val of_nativeint : nativeint -> int64
%>>
%    
%                Convert the given native integer (type nativeint)  to a 64'bit
%               integer (type int64).
%  
%<<
%  val to_nativeint : int64 -> nativeint
%>>
%    
%                Convert the given 64'bit integer (type int64) to a  native
%               integer. On 32'bit platforms, the 64'bit integer  is taken
%               modulo 2^32. On 64'bit platforms,  the conversion is exact.
%  
%<<
%  val of_string : string -> int64
%>>
%    
%                Convert the given string to a 64'bit integer.  The string is
%               read in decimal (by default) or in hexadecimal,  octal or binary
%               if the string begins with 0x, 0o or 0b  respectively.  Raise
%               Failure "int_of_string" if the given string is not  a valid
%               representation of an integer, or if the integer represented 
%               exceeds the range of integers representable in type int64.
%  
%<<
%  val to_string : int64 -> string
%>>
%    
%                Return the string representation of its argument, in decimal.
%  
%<<
%  val bits_of_float : float -> int64
%>>
%    
%                Return the internal representation of the given float according
%                to the IEEE 754 floating-point --double format-- bit layout. 
%               Bit 63 of the result represents the sign of the float;  bits 62
%               to 52 represent the (biased) exponent; bits 51 to 0  represent
%               the mantissa.
%  
%<<
%  val float_of_bits : int64 -> float
%>>
%    
%                Return the floating-point number whose internal representation,
%                according to the IEEE 754 floating-point --double format-- bit
%               layout,  is the given int64.
%  
%<<
%  type t = int64 
%>>
%    
%                An alias for the type of 64'bit integers.
%  
%<<
%  val compare : t -> t -> int
%>>
%    
%                The comparison function for 64'bit integers, with the same
%               specification as  Pervasives.compare[19.2]. Along with the type
%               t, this function compare  allows the module Int64 to be passed
%               as argument to the functors  Set.Make[20.28] and
%               Map.Make[20.18].
%  
%
%
%20.15  Module Lazy : Deferred computations.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%<<
%  type 'a t = 'a lazy_t 
%>>
%    
%                A value of type 'a Lazy.t is a deferred computation, called  a
%               suspension, that has a result of type 'a. The special 
%               expression syntax lazy (expr) makes a suspension of the 
%               computation of expr, without computing expr itself yet. 
%               "Forcing" the suspension will then compute expr and return its 
%               result.
%               Note: lazy_t is the built-in type constructor used by the
%               compiler  for the lazy keyword. You should not use it directly.
%               Always use  Lazy.t instead.
%               Note: if the program is compiled with the -rectypes option, 
%               ill-founded recursive definitions of the form let rec x = lazy x
%                or let rec x = lazy(lazy(...(lazy x))) are accepted by the
%               type'checker  and lead, when forced, to ill-formed values that
%               trigger infinite  loops in the garbage collector and other parts
%               of the run-time system.  Without the -rectypes option, such
%               ill-founded recursive definitions  are rejected by the
%               type'checker.
%  
%<<
%  exception Undefined
%>>
%   
%<<
%  val force : 'a t -> 'a
%>>
%    
%                force x forces the suspension x and returns its result.  If x
%               has already been forced, Lazy.force x returns the  same value
%               again without recomputing it. If it raised an exception,  the
%               same exception is raised again.  Raise Undefined if the forcing
%               of x tries to force x itself  recursively.
%  
%<<
%  val force_val : 'a t -> 'a
%>>
%    
%                force_val x forces the suspension x and returns its  result. If
%               x has already been forced, force_val x  returns the same value
%               again without recomputing it.  Raise Undefined if the forcing of
%               x tries to force x itself  recursively.  If the computation of x
%               raises an exception, it is unspecified  whether force_val x
%               raises the same exception or Undefined.
%  
%<<
%  val lazy_from_fun : (unit -> 'a) -> 'a t
%>>
%    
%                lazy_from_fun f is the same as lazy (f ()) but slightly more 
%               efficient.
%  
%<<
%  val lazy_from_val : 'a -> 'a t
%>>
%    
%                lazy_from_val v returns an already-forced suspension of v  This
%               is for special purposes only and should not be confused with 
%               lazy (v).
%  
%<<
%  val lazy_is_val : 'a t -> bool
%>>
%    
%                lazy_is_val x returns true if x has already been forced and 
%               did not raise an exception.
%  
%
%
%20.16  Module Lexing : The run-time library for lexers generated by ocamllex.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%
%Positions
%=========
%  
%<<
%  type position = {
%    pos_fname : string ;
%    pos_lnum : int ;
%    pos_bol : int ;
%    pos_cnum : int ;
%  }
%>>
%    
%                A value of type position describes a point in a source file. 
%               pos_fname is the file name; pos_lnum is the line number; 
%               pos_bol is the offset of the beginning of the line (number  of
%               characters between the beginning of the file and the beginning 
%               of the line); pos_cnum is the offset of the position (number of 
%               characters between the beginning of the file and the position).
%  
%<<
%  val dummy_pos : position
%>>
%    
%                A value of type position, guaranteed to be different from any 
%               valid position.
%  
%
%Lexer buffers
%=============
%  
%<<
%  type lexbuf = {
%    refill_buff : lexbuf -> unit ;
%    mutable lex_buffer : string ;
%    mutable lex_buffer_len : int ;
%    mutable lex_abs_pos : int ;
%    mutable lex_start_pos : int ;
%    mutable lex_curr_pos : int ;
%    mutable lex_last_pos : int ;
%    mutable lex_last_action : int ;
%    mutable lex_eof_reached : bool ;
%    mutable lex_mem : int array ;
%    mutable lex_start_p : position ;
%    mutable lex_curr_p : position ;
%  }
%>>
%    
%                The type of lexer buffers. A lexer buffer is the argument
%               passed  to the scanning functions defined by the generated
%               scanners.  The lexer buffer holds the current state of the
%               scanner, plus  a function to refill the buffer from the input.
%               Note that the lexing engine will only manage the pos_cnum field 
%               of lex_curr_p by updating it with the number of characters read 
%               since the start of the lexbuf. For the other fields to be 
%               accurate, they must be initialised before the first use of the 
%               lexbuf, and updated by the lexer actions.
%  
%<<
%  val from_channel : Pervasives.in_channel -> lexbuf
%>>
%    
%                Create a lexer buffer on the given input channel. 
%               Lexing.from_channel inchan returns a lexer buffer which reads 
%               from the input channel inchan, at the current reading position.
%  
%<<
%  val from_string : string -> lexbuf
%>>
%    
%                Create a lexer buffer which reads from  the given string.
%               Reading starts from the first character in  the string. An
%               end-of-input condition is generated when the  end of the string
%               is reached.
%  
%<<
%  val from_function : (string -> int -> int) -> lexbuf
%>>
%    
%                Create a lexer buffer with the given function as its reading
%               method.  When the scanner needs more characters, it will call
%               the given  function, giving it a character string s and a
%               character  count n. The function should put n characters or less
%               in s,  starting at character number 0, and return the number of
%               characters  provided. A return value of 0 means end of input.
%  
%
%Functions for lexer semantic actions
%====================================
%  
%  The following functions can be called from the semantic actions  of lexer
%definitions (the ML code enclosed in braces that  computes the value returned
%by lexing functions). They give  access to the character string matched by the
%regular expression  associated with the semantic action. These functions must
%be  applied to the argument lexbuf, which, in the code generated by  ocamllex,
%is bound to the lexer buffer passed to the parsing  function.
%<<
%  val lexeme : lexbuf -> string
%>>
%    
%                Lexing.lexeme lexbuf returns the string matched by  the regular
%               expression.
%  
%<<
%  val lexeme_char : lexbuf -> int -> char
%>>
%    
%                Lexing.lexeme_char lexbuf i returns character number i in  the
%               matched string.
%  
%<<
%  val lexeme_start : lexbuf -> int
%>>
%    
%                Lexing.lexeme_start lexbuf returns the offset in the  input
%               stream of the first character of the matched string.  The first
%               character of the stream has offset 0.
%  
%<<
%  val lexeme_end : lexbuf -> int
%>>
%    
%                Lexing.lexeme_end lexbuf returns the offset in the input stream
%                of the character following the last character of the matched 
%               string. The first character of the stream has offset 0.
%  
%<<
%  val lexeme_start_p : lexbuf -> position
%>>
%    
%                Like lexeme_start, but return a complete position instead  of
%               an offset.
%  
%<<
%  val lexeme_end_p : lexbuf -> position
%>>
%    
%                Like lexeme_end, but return a complete position instead  of an
%               offset.
%  
%
%Miscellaneous functions
%=======================
%  
%<<
%  val flush_input : lexbuf -> unit
%>>
%    
%                Discard the contents of the buffer and reset the current 
%               position to 0. The next use of the lexbuf will trigger a 
%               refill.
%  
%
%
%20.17  Module List : List operations.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  Some functions are flagged as not tail-recursive. A tail-recursive  function
%uses constant stack space, while a non-tail-recursive function  uses stack
%space proportional to the length of its list argument, which  can be a problem
%with very long lists. When the function takes several  list arguments, an
%approximate formula giving stack usage (in some  unspecified constant unit) is
%shown in parentheses.
%  The above considerations can usually be ignored if your lists are not  longer
%than about 10000 elements.
%  0.5cm
%<<
%  val length : 'a list -> int
%>>
%    
%                Return the length (number of elements) of the given list.
%  
%<<
%  val hd : 'a list -> 'a
%>>
%    
%                Return the first element of the given list. Raise  Failure "hd"
%               if the list is empty.
%  
%<<
%  val tl : 'a list -> 'a list
%>>
%    
%                Return the given list without its first element. Raise  Failure
%               "tl" if the list is empty.
%  
%<<
%  val nth : 'a list -> int -> 'a
%>>
%    
%                Return the n-th element of the given list.  The first element
%               (head of the list) is at position 0.  Raise Failure "nth" if the
%               list is too short.
%  
%<<
%  val rev : 'a list -> 'a list
%>>
%    
%                List reversal.
%  
%<<
%  val append : 'a list -> 'a list -> 'a list
%>>
%    
%                Catenate two lists. Same function as the infix operator @.  Not
%               tail-recursive (length of the first argument). The @  operator
%               is not tail-recursive either.
%  
%<<
%  val rev_append : 'a list -> 'a list -> 'a list
%>>
%    
%                List.rev_append l1 l2 reverses l1 and concatenates it to l2. 
%               This is equivalent to List.rev[20.17] l1 @ l2, but rev_append is
%                tail-recursive and more efficient.
%  
%<<
%  val concat : 'a list list -> 'a list
%>>
%    
%                Concatenate a list of lists. The elements of the argument are
%               all  concatenated together (in the same order) to give the
%               result.  Not tail-recursive  (length of the argument + length of
%               the longest sub-list).
%  
%<<
%  val flatten : 'a list list -> 'a list
%>>
%    
%                Same as concat. Not tail-recursive  (length of the argument +
%               length of the longest sub-list).
%  
%
%Iterators
%=========
%  
%<<
%  val iter : ('a -> unit) -> 'a list -> unit
%>>
%    
%                List.iter f [a1; ...; an] applies function f in turn to  a1;
%               ...; an. It is equivalent to  begin f a1; f a2; ...; f an; ()
%               end.
%  
%<<
%  val map : ('a -> 'b) -> 'a list -> 'b list
%>>
%    
%                List.map f [a1; ...; an] applies function f to a1, ..., an, 
%               and builds the list [f a1; ...; f an]  with the results returned
%               by f. Not tail-recursive.
%  
%<<
%  val rev_map : ('a -> 'b) -> 'a list -> 'b list
%>>
%    
%                List.rev_map f l gives the same result as  List.rev[20.17]
%               (List.map[20.17] f l), but is tail-recursive and  more
%               efficient.
%  
%<<
%  val fold_left : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a
%>>
%    
%                List.fold_left f a [b1; ...; bn] is  f (... (f (f a b1) b2)
%               ...) bn.
%  
%<<
%  val fold_right : ('a -> 'b -> 'b) -> 'a list -> 'b -> 'b
%>>
%    
%                List.fold_right f [a1; ...; an] b is  f a1 (f a2 (... (f an b)
%               ...)). Not tail-recursive.
%  
%
%Iterators on two lists
%======================
%  
%<<
%  val iter2 : ('a -> 'b -> unit) -> 'a list -> 'b list -> unit
%>>
%    
%                List.iter2 f [a1; ...; an] [b1; ...; bn] calls in turn  f a1
%               b1; ...; f an bn.  Raise Invalid_argument if the two lists have 
%               different lengths.
%  
%<<
%  val map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
%>>
%    
%                List.map2 f [a1; ...; an] [b1; ...; bn] is  [f a1 b1; ...; f an
%               bn].  Raise Invalid_argument if the two lists have  different
%               lengths. Not tail-recursive.
%  
%<<
%  val rev_map2 : ('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
%>>
%    
%                List.rev_map2 f l1 l2 gives the same result as  List.rev[20.17]
%               (List.map2[20.17] f l1 l2), but is tail-recursive and  more
%               efficient.
%  
%<<
%  val fold_left2 : ('a -> 'b -> 'c -> 'a) -> 'a -> 'b list -> 'c list -> 'a
%>>
%    
%                List.fold_left2 f a [b1; ...; bn] [c1; ...; cn] is  f (... (f
%               (f a b1 c1) b2 c2) ...) bn cn.  Raise Invalid_argument if the
%               two lists have  different lengths.
%  
%<<
%  val fold_right2 : ('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> 'c -> 'c
%>>
%    
%                List.fold_right2 f [a1; ...; an] [b1; ...; bn] c is  f a1 b1 (f
%               a2 b2 (... (f an bn c) ...)).  Raise Invalid_argument if the two
%               lists have  different lengths. Not tail-recursive.
%  
%
%List scanning
%=============
%  
%<<
%  val for_all : ('a -> bool) -> 'a list -> bool
%>>
%    
%                for_all p [a1; ...; an] checks if all elements of the list 
%               satisfy the predicate p. That is, it returns  (p a1) && (p a2)
%               && ... && (p an).
%  
%<<
%  val exists : ('a -> bool) -> 'a list -> bool
%>>
%    
%                exists p [a1; ...; an] checks if at least one element of  the
%               list satisfies the predicate p. That is, it returns  (p a1) ||
%               (p a2) || ... || (p an).
%  
%<<
%  val for_all2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool
%>>
%    
%                Same as List.for_all[20.17], but for a two'argument predicate. 
%               Raise Invalid_argument if the two lists have  different lengths.
%  
%<<
%  val exists2 : ('a -> 'b -> bool) -> 'a list -> 'b list -> bool
%>>
%    
%                Same as List.exists[20.17], but for a two'argument predicate. 
%               Raise Invalid_argument if the two lists have  different lengths.
%  
%<<
%  val mem : 'a -> 'a list -> bool
%>>
%    
%                mem a l is true if and only if a is equal  to an element of l.
%  
%<<
%  val memq : 'a -> 'a list -> bool
%>>
%    
%                Same as List.mem[20.17], but uses physical equality instead of
%               structural  equality to compare list elements.
%  
%
%List searching
%==============
%  
%<<
%  val find : ('a -> bool) -> 'a list -> 'a
%>>
%    
%                find p l returns the first element of the list l  that
%               satisfies the predicate p.  Raise Not_found if there is no value
%               that satisfies p in the  list l.
%  
%<<
%  val filter : ('a -> bool) -> 'a list -> 'a list
%>>
%    
%                filter p l returns all the elements of the list l  that satisfy
%               the predicate p. The order of the elements  in the input list is
%               preserved.
%  
%<<
%  val find_all : ('a -> bool) -> 'a list -> 'a list
%>>
%    
%                find_all is another name for List.filter[20.17].
%  
%<<
%  val partition : ('a -> bool) -> 'a list -> 'a list * 'a list
%>>
%    
%                partition p l returns a pair of lists (l1, l2), where  l1 is
%               the list of all the elements of l that  satisfy the predicate p,
%               and l2 is the list of all the  elements of l that do not satisfy
%               p.  The order of the elements in the input list is preserved.
%  
%
%Association lists
%=================
%  
%<<
%  val assoc : 'a -> ('a * 'b) list -> 'b
%>>
%    
%                assoc a l returns the value associated with key a in the list
%               of  pairs l. That is,  assoc a [ ...; (a,b); ...] = b  if (a,b)
%               is the leftmost binding of a in list l.  Raise Not_found if
%               there is no value associated with a in the  list l.
%  
%<<
%  val assq : 'a -> ('a * 'b) list -> 'b
%>>
%    
%                Same as List.assoc[20.17], but uses physical equality instead
%               of structural  equality to compare keys.
%  
%<<
%  val mem_assoc : 'a -> ('a * 'b) list -> bool
%>>
%    
%                Same as List.assoc[20.17], but simply return true if a binding
%               exists,  and false if no bindings exist for the given key.
%  
%<<
%  val mem_assq : 'a -> ('a * 'b) list -> bool
%>>
%    
%                Same as List.mem_assoc[20.17], but uses physical equality
%               instead of  structural equality to compare keys.
%  
%<<
%  val remove_assoc : 'a -> ('a * 'b) list -> ('a * 'b) list
%>>
%    
%                remove_assoc a l returns the list of  pairs l without the first
%               pair with key a, if any.  Not tail-recursive.
%  
%<<
%  val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list
%>>
%    
%                Same as List.remove_assoc[20.17], but uses physical equality
%               instead  of structural equality to compare keys. Not
%               tail-recursive.
%  
%
%Lists of pairs
%==============
%  
%<<
%  val split : ('a * 'b) list -> 'a list * 'b list
%>>
%    
%                Transform a list of pairs into a pair of lists:  split
%               [(a1,b1); ...; (an,bn)] is ([a1; ...; an], [b1; ...; bn]).  Not
%               tail-recursive.
%  
%<<
%  val combine : 'a list -> 'b list -> ('a * 'b) list
%>>
%    
%                Transform a pair of lists into a list of pairs:  combine [a1;
%               ...; an] [b1; ...; bn] is  [(a1,b1); ...; (an,bn)].  Raise
%               Invalid_argument if the two lists  have different lengths. Not
%               tail-recursive.
%  
%
%Sorting
%=======
%  
%<<
%  val sort : ('a -> 'a -> int) -> 'a list -> 'a list
%>>
%    
%                Sort a list in increasing order according to a comparison 
%               function. The comparison function must return 0 if its arguments
%                compare as equal, a positive integer if the first is greater, 
%               and a negative integer if the first is smaller (see Array.sort
%               for  a complete specification). For example, 
%               Pervasives.compare[19.2] is a suitable comparison function.  The
%               resulting list is sorted in increasing order.  List.sort is
%               guaranteed to run in constant heap space  (in addition to the
%               size of the result list) and logarithmic  stack space.
%               The current implementation uses Merge Sort. It runs in constant 
%               heap space and logarithmic stack space.
%  
%<<
%  val stable_sort : ('a -> 'a -> int) -> 'a list -> 'a list
%>>
%    
%                Same as List.sort[20.17], but the sorting algorithm is
%               guaranteed to  be stable (i.e. elements that compare equal are
%               kept in their  original order) .
%               The current implementation uses Merge Sort. It runs in constant 
%               heap space and logarithmic stack space.
%  
%<<
%  val fast_sort : ('a -> 'a -> int) -> 'a list -> 'a list
%>>
%    
%                Same as List.sort[20.17] or List.stable_sort[20.17], whichever
%               is faster  on typical input.
%  
%<<
%  val merge : ('a -> 'a -> int) -> 'a list -> 'a list -> 'a list
%>>
%    
%                Merge two lists:  Assuming that l1 and l2 are sorted according
%               to the  comparison function cmp, merge cmp l1 l2 will return a 
%               sorted list containting all the elements of l1 and l2.  If
%               several elements compare equal, the elements of l1 will be 
%               before the elements of l2.  Not tail-recursive (sum of the
%               lengths of the arguments).
%  
%
%
%20.18  Module Map : Association tables over ordered types.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module implements applicative association tables, also known as  finite
%maps or dictionaries, given a total ordering function  over the keys.  All
%operations over maps are purely applicative (no side-effects).  The
%implementation uses balanced binary trees, and therefore searching  and
%insertion take time logarithmic in the size of the map.
%  0.5cm
%<<
%  module type OrderedType = >>
%   
%    sig
% 
%  
%   <<
%     type t 
%   >>
%   
%                   The type of the map keys.
% 
%   <<
%     val compare : t -> t -> int
%   >>
%   
%                   A total ordering function over the keys.  This is a
%                  two'argument function f such that  f e1 e2 is zero if the
%                  keys e1 and e2 are equal,  f e1 e2 is strictly negative if e1
%                  is smaller than e2,  and f e1 e2 is strictly positive if e1
%                  is greater than e2.  Example: a suitable ordering function is
%                  the generic structural  comparison function
%                  Pervasives.compare[19.2].
% 
%  
%  -  end
%  
%                Input signature of the functor Map.Make[20.18].
%  
%<<
%  module type S = >>
%   
%    sig
% 
%  
%   <<
%     type key 
%   >>
%   
%                   The type of the map keys.
% 
%   <<
%     type +'a t 
%   >>
%   
%                   The type of maps from type key to type 'a.
% 
%   <<
%     val empty : 'a t
%   >>
%   
%                   The empty map.
% 
%   <<
%     val is_empty : 'a t -> bool
%   >>
%   
%                   Test whether a map is empty or not.
% 
%   <<
%     val add : key -> 'a -> 'a t -> 'a t
%   >>
%   
%                   add x y m returns a map containing the same bindings as  m,
%                  plus a binding of x to y. If x was already bound  in m, its
%                  previous binding disappears.
% 
%   <<
%     val find : key -> 'a t -> 'a
%   >>
%   
%                   find x m returns the current binding of x in m,  or raises
%                  Not_found if no such binding exists.
% 
%   <<
%     val remove : key -> 'a t -> 'a t
%   >>
%   
%                   remove x m returns a map containing the same bindings as  m,
%                  except for x which is unbound in the returned map.
% 
%   <<
%     val mem : key -> 'a t -> bool
%   >>
%   
%                   mem x m returns true if m contains a binding for x,  and
%                  false otherwise.
% 
%   <<
%     val iter : (key -> 'a -> unit) -> 'a t -> unit
%   >>
%   
%                   iter f m applies f to all bindings in map m.  f receives the
%                  key as first argument, and the associated value  as second
%                  argument. The bindings are passed to f in increasing  order
%                  with respect to the ordering over the type of the keys.  Only
%                  current bindings are presented to f:  bindings hidden by more
%                  recent bindings are not passed to f.
% 
%   <<
%     val map : ('a -> 'b) -> 'a t -> 'b t
%   >>
%   
%                   map f m returns a map with same domain as m, where the 
%                  associated value a of all bindings of m has been  replaced by
%                  the result of the application of f to a.  The bindings are
%                  passed to f in increasing order  with respect to the ordering
%                  over the type of the keys.
% 
%   <<
%     val mapi : (key -> 'a -> 'b) -> 'a t -> 'b t
%   >>
%   
%                   Same as Map.S.map[20.18], but the function receives as
%                  arguments both the  key and the associated value for each
%                  binding of the map.
% 
%   <<
%     val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
%   >>
%   
%                   fold f m a computes (f kN dN ... (f k1 d1 a)...),  where k1
%                  ... kN are the keys of all bindings in m  (in increasing
%                  order), and d1 ... dN are the associated data.
% 
%   <<
%     val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
%   >>
%   
%                   Total ordering between maps. The first argument is a total
%                  ordering  used to compare data associated with equal keys in
%                  the two maps.
% 
%   <<
%     val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
%   >>
%   
%                   equal cmp m1 m2 tests whether the maps m1 and m2 are  equal,
%                  that is, contain equal keys and associate them with  equal
%                  data. cmp is the equality predicate used to compare  the data
%                  associated with the keys.
% 
%  
%  -  end
%  
%                Output signature of the functor Map.Make[20.18].
%  
%<<
%  module Make : >>
%   
%  functor (Ord : OrderedType) -> S  with type key = Ord.t
%                Functor building an implementation of the map structure  given
%               a totally ordered type.
%  
%
%
%20.19  Module Marshal : Marshaling of data structures.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module provides functions to encode arbitrary data structures  as
%sequences of bytes, which can then be written on a file or  sent over a pipe or
%network connection. The bytes can then  be read back later, possibly in another
%process, and decoded back  into a data structure. The format for the byte
%sequences  is compatible across all machines for a given version of Objective
%Caml.
%  Warning: marshaling is currently not type-safe. The type  of marshaled data
%is not transmitted along the value of the data,  making it impossible to check
%that the data read back possesses the  type expected by the context. In
%particular, the result type of  the Marshal.from_* functions is given as 'a,
%but this is  misleading: the returned Caml value does not possess type 'a  for
%all 'a; it has one, unique type which cannot be determined  at compile-type.
%The programmer should explicitly give the expected  type of the returned value,
%using the following syntax:
%  
% - (Marshal.from_channel chan : type).  Anything can happen at run-time if the
%   object in the file does not  belong to the given type. 
%  
%  The representation of marshaled values is not human-readable,  and uses bytes
%that are not printable characters. Therefore,  input and output channels used
%in conjunction with Marshal.to_channel  and Marshal.from_channel must be opened
%in binary mode, using e.g.  open_out_bin or open_in_bin; channels opened in
%text mode will  cause unmarshaling errors on platforms where text channels
%behave  differently than binary channels, e.g. Windows.
%  0.5cm
%<<
%  type extern_flags =
%    | No_sharing
%>>
%   
%                Don-t preserve sharing 
%   
%<<
%    | Closures
%>>
%   
%                Send function closures 
%    
%                The flags to the Marshal.to_* functions below.
%  
%<<
%  val to_channel : Pervasives.out_channel -> 'a -> extern_flags list -> unit
%>>
%    
%                Marshal.to_channel chan v flags writes the representation  of v
%               on channel chan. The flags argument is a  possibly empty list of
%               flags that governs the marshaling  behavior with respect to
%               sharing and functional values.
%               If flags does not contain Marshal.No_sharing, circularities  
%               and sharing inside the value v are detected and preserved  in
%               the sequence of bytes produced. In particular, this  guarantees
%               that marshaling always terminates. Sharing  between values
%               marshaled by successive calls to  Marshal.to_channel is not
%               detected, though.  If flags contains Marshal.No_sharing, sharing
%               is ignored.  This results in faster marshaling if v contains no
%               shared  substructures, but may cause slower marshaling and
%               larger  byte representations if v actually contains sharing,  or
%               even non-termination if v contains cycles.
%               If flags does not contain Marshal.Closures,  marshaling fails
%               when it encounters a functional value  inside v: only --pure--
%               data structures, containing neither  functions nor objects, can
%               safely be transmitted between  different programs. If flags
%               contains Marshal.Closures,  functional values will be marshaled
%               as a position in the code  of the program. In this case, the
%               output of marshaling can  only be read back in processes that
%               run exactly the same program,  with exactly the same compiled
%               code. (This is checked  at un-marshaling time, using an MD5
%               digest of the code  transmitted along with the code position.)
%  
%<<
%  val to_string : 'a -> extern_flags list -> string
%>>
%    
%                Marshal.to_string v flags returns a string containing  the
%               representation of v as a sequence of bytes.  The flags argument
%               has the same meaning as for  Marshal.to_channel[20.19].
%  
%<<
%  val to_buffer : string -> int -> int -> 'a -> extern_flags list -> int
%>>
%    
%                Marshal.to_buffer buff ofs len v flags marshals the value v, 
%               storing its byte representation in the string buff,  starting at
%               character number ofs, and writing at most  len characters. It
%               returns the number of characters  actually written to the
%               string. If the byte representation  of v does not fit in len
%               characters, the exception Failure  is raised.
%  
%<<
%  val from_channel : Pervasives.in_channel -> 'a
%>>
%    
%                Marshal.from_channel chan reads from channel chan the  byte
%               representation of a structured value, as produced by  one of the
%               Marshal.to_* functions, and reconstructs and  returns the
%               corresponding value.
%  
%<<
%  val from_string : string -> int -> 'a
%>>
%    
%                Marshal.from_string buff ofs unmarshals a structured value 
%               like Marshal.from_channel[20.19] does, except that the byte 
%               representation is not read from a channel, but taken from  the
%               string buff, starting at position ofs.
%  
%<<
%  val header_size : int
%>>
%    
%                The bytes representing a marshaled value are composed of  a
%               fixed-size header and a variable-sized data part,  whose size
%               can be determined from the header.  Marshal.header_size[20.19]
%               is the size, in characters, of the header. 
%               Marshal.data_size[20.19] buff ofs is the size, in characters, 
%               of the data part, assuming a valid header is stored in  buff
%               starting at position ofs.  Finally, Marshal.total_size[20.19]
%               buff ofs is the total size,  in characters, of the marshaled
%               value.  Both Marshal.data_size[20.19] and
%               Marshal.total_size[20.19] raise Failure  if buff, ofs does not
%               contain a valid header.
%               To read the byte representation of a marshaled value into  a
%               string buffer, the program needs to read first 
%               Marshal.header_size[20.19] characters into the buffer,  then
%               determine the length of the remainder of the  representation
%               using Marshal.data_size[20.19],  make sure the buffer is large
%               enough to hold the remaining  data, then read it, and finally
%               call Marshal.from_string[20.19]  to unmarshal the value.
%  
%<<
%  val data_size : string -> int -> int
%>>
%    
%                See Marshal.header_size[20.19].
%  
%<<
%  val total_size : string -> int -> int
%>>
%    
%                See Marshal.header_size[20.19].
%  
%
%
%20.20  Module Nativeint : Processor-native integers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module provides operations on the type nativeint of  signed 32'bit
%integers (on 32'bit platforms) or  signed 64'bit integers (on 64'bit
%platforms).  This integer type has exactly the same width as that of a long 
%integer type in the C compiler. All arithmetic operations over  nativeint are
%taken modulo 2^32 or 2^64 depending  on the word size of the architecture.
%  Performance notice: values of type nativeint occupy more memory  space than
%values of type int, and arithmetic operations on  nativeint are generally
%slower than those on int. Use nativeint  only when the application requires the
%extra bit of precision  over the int type.
%  0.5cm
%<<
%  val zero : nativeint
%>>
%    
%                The native integer 0.
%  
%<<
%  val one : nativeint
%>>
%    
%                The native integer 1.
%  
%<<
%  val minus_one : nativeint
%>>
%    
%                The native integer -1.
%  
%<<
%  val neg : nativeint -> nativeint
%>>
%    
%                Unary negation.
%  
%<<
%  val add : nativeint -> nativeint -> nativeint
%>>
%    
%                Addition.
%  
%<<
%  val sub : nativeint -> nativeint -> nativeint
%>>
%    
%                Subtraction.
%  
%<<
%  val mul : nativeint -> nativeint -> nativeint
%>>
%    
%                Multiplication.
%  
%<<
%  val div : nativeint -> nativeint -> nativeint
%>>
%    
%                Integer division. Raise Division_by_zero if the second  
%               argument is zero. This division rounds the real quotient of  its
%               arguments towards zero, as specified for Pervasives.(/)[19.2].
%  
%<<
%  val rem : nativeint -> nativeint -> nativeint
%>>
%    
%                Integer remainder. If y is not zero, the result  of
%               Nativeint.rem x y satisfies the following properties: 
%               Nativeint.zero <= Nativeint.rem x y < Nativeint.abs y and  x =
%               Nativeint.add (Nativeint.mul (Nativeint.div x y) y)
%               (Nativeint.rem x y).  If y = 0, Nativeint.rem x y raises
%               Division_by_zero.
%  
%<<
%  val succ : nativeint -> nativeint
%>>
%    
%                Successor.  Nativeint.succ x is Nativeint.add x Nativeint.one.
%  
%<<
%  val pred : nativeint -> nativeint
%>>
%    
%                Predecessor.  Nativeint.pred x is Nativeint.sub x
%               Nativeint.one.
%  
%<<
%  val abs : nativeint -> nativeint
%>>
%    
%                Return the absolute value of its argument.
%  
%<<
%  val size : int
%>>
%    
%                The size in bits of a native integer. This is equal to 32  on a
%               32'bit platform and to 64 on a 64'bit platform.
%  
%<<
%  val max_int : nativeint
%>>
%    
%                The greatest representable native integer,  either 2^31 - 1 on
%               a 32'bit platform,  or 2^63 - 1 on a 64'bit platform.
%  
%<<
%  val min_int : nativeint
%>>
%    
%                The greatest representable native integer,  either -2^31 on a
%               32'bit platform,  or -2^63 on a 64'bit platform.
%  
%<<
%  val logand : nativeint -> nativeint -> nativeint
%>>
%    
%                Bitwise logical and.
%  
%<<
%  val logor : nativeint -> nativeint -> nativeint
%>>
%    
%                Bitwise logical or.
%  
%<<
%  val logxor : nativeint -> nativeint -> nativeint
%>>
%    
%                Bitwise logical exclusive or.
%  
%<<
%  val lognot : nativeint -> nativeint
%>>
%    
%                Bitwise logical negation
%  
%<<
%  val shift_left : nativeint -> int -> nativeint
%>>
%    
%                Nativeint.shift_left x y shifts x to the left by y bits.  The
%               result is unspecified if y < 0 or y >= bitsize,  where bitsize
%               is 32 on a 32'bit platform and  64 on a 64'bit platform.
%  
%<<
%  val shift_right : nativeint -> int -> nativeint
%>>
%    
%                Nativeint.shift_right x y shifts x to the right by y bits. 
%               This is an arithmetic shift: the sign bit of x is replicated 
%               and inserted in the vacated bits.  The result is unspecified if
%               y < 0 or y >= bitsize.
%  
%<<
%  val shift_right_logical : nativeint -> int -> nativeint
%>>
%    
%                Nativeint.shift_right_logical x y shifts x to the right  by y
%               bits.  This is a logical shift: zeroes are inserted in the
%               vacated bits  regardless of the sign of x.  The result is
%               unspecified if y < 0 or y >= bitsize.
%  
%<<
%  val of_int : int -> nativeint
%>>
%    
%                Convert the given integer (type int) to a native integer  (type
%               nativeint).
%  
%<<
%  val to_int : nativeint -> int
%>>
%    
%                Convert the given native integer (type nativeint) to an 
%               integer (type int). The high-order bit is lost during  the
%               conversion.
%  
%<<
%  val of_float : float -> nativeint
%>>
%    
%                Convert the given floating-point number to a native integer, 
%               discarding the fractional part (truncate towards 0).  The result
%               of the conversion is undefined if, after truncation,  the number
%               is outside the range  [Nativeint.min_int[20.20],
%               Nativeint.max_int[20.20]].
%  
%<<
%  val to_float : nativeint -> float
%>>
%    
%                Convert the given native integer to a floating-point number.
%  
%<<
%  val of_int32 : int32 -> nativeint
%>>
%    
%                Convert the given 32'bit integer (type int32)  to a native
%               integer.
%  
%<<
%  val to_int32 : nativeint -> int32
%>>
%    
%                Convert the given native integer to a  32'bit integer (type
%               int32). On 64'bit platforms,  the 64'bit native integer is taken
%               modulo 2^32,  i.e. the top 32 bits are lost. On 32'bit
%               platforms,  the conversion is exact.
%  
%<<
%  val of_string : string -> nativeint
%>>
%    
%                Convert the given string to a native integer.  The string is
%               read in decimal (by default) or in hexadecimal,  octal or binary
%               if the string begins with 0x, 0o or 0b  respectively.  Raise
%               Failure "int_of_string" if the given string is not  a valid
%               representation of an integer, or if the integer represented 
%               exceeds the range of integers representable in type nativeint.
%  
%<<
%  val to_string : nativeint -> string
%>>
%    
%                Return the string representation of its argument, in decimal.
%  
%<<
%  type t = nativeint 
%>>
%    
%                An alias for the type of native integers.
%  
%<<
%  val compare : t -> t -> int
%>>
%    
%                The comparison function for native integers, with the same
%               specification as  Pervasives.compare[19.2]. Along with the type
%               t, this function compare  allows the module Nativeint to be
%               passed as argument to the functors  Set.Make[20.28] and
%               Map.Make[20.18].
%  
%
%
%20.21  Module Oo : Operations on objects
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  val copy : (< .. > as 'a) -> 'a
%>>
%    
%                Oo.copy o returns a copy of object o, that is a fresh  object
%               with the same methods and instance variables as o
%  
%<<
%  val id : < .. > -> int
%>>
%    
%                Return an integer identifying this object, unique for  the
%               current execution of the program.
%  
%
%
%20.22  Module Parsing : The run-time library for parsers generated by
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%ocamlyacc.
%*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  val symbol_start : unit -> int
%>>
%    
%                symbol_start and Parsing.symbol_end[20.22] are to be called in
%               the  action part of a grammar rule only. They return the offset
%               of the  string that matches the left-hand side of the rule:
%               symbol_start()  returns the offset of the first character;
%               symbol_end() returns the  offset after the last character. The
%               first character in a file is at  offset 0.
%  
%<<
%  val symbol_end : unit -> int
%>>
%    
%                See Parsing.symbol_start[20.22].
%  
%<<
%  val rhs_start : int -> int
%>>
%    
%                Same as Parsing.symbol_start[20.22] and
%               Parsing.symbol_end[20.22], but  return the offset of the string
%               matching the nth item on the  right-hand side of the rule, where
%               n is the integer parameter  to rhs_start and rhs_end. n is 1 for
%               the leftmost item.
%  
%<<
%  val rhs_end : int -> int
%>>
%    
%                See Parsing.rhs_start[20.22].
%  
%<<
%  val symbol_start_pos : unit -> Lexing.position
%>>
%    
%                Same as symbol_start, but return a position instead of an
%               offset.
%  
%<<
%  val symbol_end_pos : unit -> Lexing.position
%>>
%    
%                Same as symbol_end, but return a position instead of an offset.
%  
%<<
%  val rhs_start_pos : int -> Lexing.position
%>>
%    
%                Same as rhs_start, but return a position instead of an offset.
%  
%<<
%  val rhs_end_pos : int -> Lexing.position
%>>
%    
%                Same as rhs_end, but return a position instead of an offset.
%  
%<<
%  val clear_parser : unit -> unit
%>>
%    
%                Empty the parser stack. Call it just after a parsing function 
%               has returned, to remove all pointers from the parser stack  to
%               structures that were built by semantic actions during parsing. 
%               This is optional, but lowers the memory requirements of the 
%               programs.
%  
%<<
%  exception Parse_error
%>>
%    
%                Raised when a parser encounters a syntax error.  Can also be
%               raised from the action part of a grammar rule,  to initiate
%               error recovery.
%  
%
%
%20.23  Module Printexc : Facilities for printing exceptions.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  val to_string : exn -> string
%>>
%    
%                Printexc.to_string e returns a string representation of  the
%               exception e.
%  
%<<
%  val print : ('a -> 'b) -> 'a -> 'b
%>>
%    
%                Printexc.print fn x applies fn to x and returns the result.  If
%               the evaluation of fn x raises any exception, the  name of the
%               exception is printed on standard error output,  and the
%               exception is raised again.  The typical use is to catch and
%               report exceptions that  escape a function application.
%  
%<<
%  val catch : ('a -> 'b) -> 'a -> 'b
%>>
%    
%                Printexc.catch fn x is similar to Printexc.print[20.23], but 
%               aborts the program with exit code 2 after printing the  uncaught
%               exception. This function is deprecated: the runtime  system is
%               now able to print uncaught exceptions as precisely  as
%               Printexc.catch does. Moreover, calling Printexc.catch  makes it
%               harder to track the location of the exception  using the
%               debugger or the stack backtrace facility.  So, do not use
%               Printexc.catch in new code.
%  
%
%
%20.24  Module Printf : Formatted output functions.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  val fprintf :
%    Pervasives.out_channel ->
%    ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a
%>>
%    
%                fprintf outchan format arg1 ... argN formats the arguments 
%               arg1 to argN according to the format string format,  and outputs
%               the resulting string on the channel outchan.
%               The format is a character string which contains two types of 
%               objects: plain characters, which are simply copied to the 
%               output channel, and conversion specifications, each of which 
%               causes conversion and printing of one argument.
%               Conversion specifications consist in the % character, followed 
%               by optional flags and field widths, followed by one or two
%               conversion  character. The conversion characters and their
%               meanings are:
%                 
%                - d, i, n, or N: convert an integer argument to signed decimal.
%                  
%                - u: convert an integer argument to unsigned decimal. 
%                - x: convert an integer argument to unsigned hexadecimal, 
%                  using lowercase letters. 
%                - X: convert an integer argument to unsigned hexadecimal, 
%                  using uppercase letters. 
%                - o: convert an integer argument to unsigned octal. 
%                - s: insert a string argument. 
%                - S: insert a string argument in Caml syntax (double quotes,
%                  escapes). 
%                - c: insert a character argument. 
%                - C: insert a character argument in Caml syntax (single quotes,
%                  escapes). 
%                - f: convert a floating-point argument to decimal notation,  in
%                  the style dddd.ddd. 
%                - F: convert a floating-point argument in Caml syntax (dddd.ddd
%                   with a mandatory .). 
%                - e or E: convert a floating-point argument to decimal
%                  notation,  in the style d.ddd e+-dd (mantissa and exponent). 
%                - g or G: convert a floating-point argument to decimal
%                  notation,  in style f or e, E (whichever is more compact). 
%                - B: convert a boolean argument to the string true or false 
%                - b: convert a boolean argument (for backward compatibility; do
%                  not  use in new programs). 
%                - ld, li, lu, lx, lX, lo: convert an int32 argument to  the
%                  format specified by the second letter (decimal, hexadecimal,
%                  etc). 
%                - nd, ni, nu, nx, nX, no: convert a nativeint argument to  the
%                  format specified by the second letter. 
%                - Ld, Li, Lu, Lx, LX, Lo: convert an int64 argument to  the
%                  format specified by the second letter. 
%                - a: user-defined printer. Takes two arguments and apply the
%                  first  one to outchan (the current output channel) and to the
%                  second  argument. The first argument must therefore have type
%                   out_channel -> 'b -> unit and the second 'b.  The output
%                  produced by the function is therefore inserted  in the output
%                  of fprintf at the current point. 
%                - t: same as %a, but takes only one argument (with type 
%                  out_channel -> unit) and apply it to outchan. 
%                - !: take no argument and flush the output. 
%                - %: take no argument and output one % character. 
%               
%               The optional flags include:
%                 
%                - -: left-justify the output (default is right justification). 
%                - 0: for numerical conversions, pad with zeroes instead of
%                  spaces. 
%                - +: for numerical conversions, prefix number with a + sign if
%                  positive. 
%                - space: for numerical conversions, prefix number with a space
%                  if positive. 
%                - `#': request an alternate formatting style for numbers. 
%               
%               The field widths are composed of an optional integer literal 
%               indicating the minimal width of the result, possibly followed by
%                a dot . and another integer literal indicating how many digits 
%               follow the decimal point in the %f, %e, and %E conversions.  For
%               instance, %6d prints an integer, prefixing it with spaces to 
%               fill at least 6 characters; and %.4f prints a float with 4 
%               fractional digits. Each or both of the integer literals can also
%               be  specified as a *, in which case an extra integer argument is
%               taken  to specify the corresponding width or precision.
%               Warning: if too few arguments are provided,  for instance
%               because the printf function is partially  applied, the format is
%               immediately printed up to  the conversion of the first missing
%               argument; printing  will then resume when the missing arguments
%               are provided.  For example, List.iter (printf "x=%d y=%d " 1)
%               [2;3]  prints x=1 y=2 3 instead of the expected  x=1 y=2 x=1
%               y=3. To get the expected behavior, do  List.iter (fun y ->
%               printf "x=%d y=%d " 1 y) [2;3].
%  
%<<
%  val printf : ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a
%>>
%    
%                Same as Printf.fprintf[20.24], but output on stdout.
%  
%<<
%  val eprintf : ('a, Pervasives.out_channel, unit) Pervasives.format -> 'a
%>>
%    
%                Same as Printf.fprintf[20.24], but output on stderr.
%  
%<<
%  val sprintf : ('a, unit, string) Pervasives.format -> 'a
%>>
%    
%                Same as Printf.fprintf[20.24], but instead of printing on an
%               output channel,  return a string containing the result of
%               formatting  the arguments.
%  
%<<
%  val bprintf : Buffer.t -> ('a, Buffer.t, unit) Pervasives.format -> 'a
%>>
%    
%                Same as Printf.fprintf[20.24], but instead of printing on an
%               output channel,  append the formatted arguments to the given
%               extensible buffer  (see module Buffer[20.3]).
%  
%<<
%  val kprintf : (string -> 'a) -> ('b, unit, string, 'a) format4 -> 'b
%>>
%    
%                kprintf k format arguments is the same as sprintf format
%               arguments,  except that the resulting string is passed as
%               argument to k; the  result of k is then returned as the result
%               of kprintf.
%  
%
%
%20.25  Module Queue : First-in first-out queues.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module implements queues (FIFOs), with in-place modification.
%  0.5cm
%<<
%  type 'a t 
%>>
%    
%                The type of queues containing elements of type 'a.
%  
%<<
%  exception Empty
%>>
%    
%                Raised when Queue.take[20.25] or Queue.peek[20.25] is applied
%               to an empty queue.
%  
%<<
%  val create : unit -> 'a t
%>>
%    
%                Return a new queue, initially empty.
%  
%<<
%  val add : 'a -> 'a t -> unit
%>>
%    
%                add x q adds the element x at the end of the queue q.
%  
%<<
%  val push : 'a -> 'a t -> unit
%>>
%    
%                push is a synonym for add.
%  
%<<
%  val take : 'a t -> 'a
%>>
%    
%                take q removes and returns the first element in queue q,  or
%               raises Empty if the queue is empty.
%  
%<<
%  val pop : 'a t -> 'a
%>>
%    
%                pop is a synonym for take.
%  
%<<
%  val peek : 'a t -> 'a
%>>
%    
%                peek q returns the first element in queue q, without removing 
%               it from the queue, or raises Empty if the queue is empty.
%  
%<<
%  val top : 'a t -> 'a
%>>
%    
%                top is a synonym for peek.
%  
%<<
%  val clear : 'a t -> unit
%>>
%    
%                Discard all elements from a queue.
%  
%<<
%  val copy : 'a t -> 'a t
%>>
%    
%                Return a copy of the given queue.
%  
%<<
%  val is_empty : 'a t -> bool
%>>
%    
%                Return true if the given queue is empty, false otherwise.
%  
%<<
%  val length : 'a t -> int
%>>
%    
%                Return the number of elements in a queue.
%  
%<<
%  val iter : ('a -> unit) -> 'a t -> unit
%>>
%    
%                iter f q applies f in turn to all elements of q,  from the
%               least recently entered to the most recently entered.  The queue
%               itself is unchanged.
%  
%<<
%  val fold : ('a -> 'b -> 'a) -> 'a -> 'b t -> 'a
%>>
%    
%                fold f accu q is equivalent to List.fold_left f accu l,  where
%               l is the list of q-s elements. The queue remains  unchanged.
%  
%<<
%  val transfer : 'a t -> 'a t -> unit
%>>
%    
%                transfer q1 q2 adds all of q1-s elements at the end of  the
%               queue q2, then clears q1. It is equivalent to the  sequence iter
%               (fun x -> add x q2) q1; clear q1, but runs  in constant time.
%  
%
%
%20.26  Module Random : Pseudo-random number generators (PRNG).
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%
%Basic functions
%===============
%  
%<<
%  val init : int -> unit
%>>
%    
%                Initialize the generator, using the argument as a seed.  The
%               same seed will always yield the same sequence of numbers.
%  
%<<
%  val full_init : int array -> unit
%>>
%    
%                Same as Random.init[20.26] but takes more data as seed.
%  
%<<
%  val self_init : unit -> unit
%>>
%    
%                Initialize the generator with a more-or-less random seed chosen
%                in a system-dependent way.
%  
%<<
%  val bits : unit -> int
%>>
%    
%                Return 30 random bits in a nonnegative integer.
%  
%<<
%  val int : int -> int
%>>
%    
%                Random.int bound returns a random integer between 0 (inclusive)
%                and bound (exclusive). bound must be more than 0 and less  than
%               2^30.
%  
%<<
%  val int32 : Int32.t -> Int32.t
%>>
%    
%                Random.int32 bound returns a random integer between 0
%               (inclusive)  and bound (exclusive). bound must be greater than
%               0.
%  
%<<
%  val nativeint : Nativeint.t -> Nativeint.t
%>>
%    
%                Random.nativeint bound returns a random integer between 0
%               (inclusive)  and bound (exclusive). bound must be greater than
%               0.
%  
%<<
%  val int64 : Int64.t -> Int64.t
%>>
%    
%                Random.int64 bound returns a random integer between 0
%               (inclusive)  and bound (exclusive). bound must be greater than
%               0.
%  
%<<
%  val float : float -> float
%>>
%    
%                Random.float bound returns a random floating-point number 
%               between 0 (inclusive) and bound (exclusive). If bound is 
%               negative, the result is negative or zero. If bound is 0,  the
%               result is 0.
%  
%<<
%  val bool : unit -> bool
%>>
%    
%                Random.bool () returns true or false with probability 0.5 each.
%  
%
%Advanced functions
%==================
%  
%  The functions from module State manipulate the current state  of the random
%generator explicitely.  This allows using one or several deterministic PRNGs, 
%even in a multi-threaded program, without interference from  other parts of the
%program.
%<<
%  module State : >>
%   
%    sig
% 
%  
%   <<
%     type t 
%   >>
%   
%                   The type of PRNG states.
% 
%   <<
%     val make : int array -> t
%   >>
%   
%                   Create a new state and initialize it with the given seed.
% 
%   <<
%     val make_self_init : unit -> t
%   >>
%   
%                   Create a new state and initialize it with a system-dependent
%                   low-entropy seed.
% 
%   <<
%     val copy : t -> t
%   >>
%   
%                   Return a copy of the given state.
% 
%   <<
%     val bits : t -> int
%   >>
%  
%   <<
%     val int : t -> int -> int
%   >>
%  
%   <<
%     val int32 : t -> Int32.t -> Int32.t
%   >>
%  
%   <<
%     val nativeint : t -> Nativeint.t -> Nativeint.t
%   >>
%  
%   <<
%     val int64 : t -> Int64.t -> Int64.t
%   >>
%  
%   <<
%     val float : t -> float -> float
%   >>
%  
%   <<
%     val bool : t -> bool
%   >>
%   
%                   These functions are the same as the basic functions, except
%                  that they  use (and update) the given PRNG state instead of
%                  the default one.
% 
%  
%  -  end
%  
%<<
%  val get_state : unit -> State.t
%>>
%    
%                Return the current state of the generator used by the basic
%               functions.
%  
%<<
%  val set_state : State.t -> unit
%>>
%    
%                Set the state of the generator used by the basic functions.
%  
%
%
%20.27  Module Scanf : Formatted input functions.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  module Scanning : >>
%   
%    sig
% 
%  
%   <<
%     type scanbuf 
%   >>
%   
%                   The type of scanning buffers. A scanning buffer is the
%                  argument passed  to the scanning functions used by the scanf
%                  family of functions.  The scanning buffer holds the current
%                  state of the scan, plus  a function to get the next char from
%                  the input, and a token buffer  to store the string matched so
%                  far.
% 
%   <<
%     val stdib : scanbuf
%   >>
%   
%                   The scanning buffer reading from stdin.  stdib is equivalent
%                  to Scanning.from_channel stdin.
% 
%   <<
%     val from_string : string -> scanbuf
%   >>
%   
%                   Scanning.from_string s returns a scanning buffer which reads
%                   from the given string.  Reading starts from the first
%                  character in the string.  The end-of-input condition is set
%                  when the end of the string is reached.
% 
%   <<
%     val from_file : string -> scanbuf
%   >>
%   
%                   Bufferized file reading in text mode. The efficient and
%                  usual  way to scan text mode files (in effect, from_file
%                  returns a  buffer that reads characters in large chunks,
%                  rather than one  character at a time as buffers returned by
%                  from_channel do).  Scanning.from_file fname returns a
%                  scanning buffer which reads  from the given file fname in
%                  text mode.
% 
%   <<
%     val from_file_bin : string -> scanbuf
%   >>
%   
%                   Bufferized file reading in binary mode.
% 
%   <<
%     val from_function : (unit -> char) -> scanbuf
%   >>
%   
%                   Scanning.from_function f returns a scanning buffer with  the
%                  given function as its reading method.  When scanning needs
%                  one more character, the given function is called.  When the
%                  function has no more character to provide, it must signal  an
%                  end-of-input condition by raising the exception End_of_file.
% 
%   <<
%     val from_channel : Pervasives.in_channel -> scanbuf
%   >>
%   
%                   Scanning.from_channel inchan returns a scanning buffer which
%                  reads  one character at a time from the input channel inchan,
%                  starting at the  current reading position.
% 
%   <<
%     val end_of_input : scanbuf -> bool
%   >>
%   
%                   Scanning.end_of_input scanbuf tests the end of input
%                  condition  of the given buffer.
% 
%   <<
%     val beginning_of_input : scanbuf -> bool
%   >>
%   
%                   Scanning.beginning_of_input scanbuf tests the beginning of
%                  input  condition of the given buffer.
% 
%  
%  -  end
%  
%                Scanning buffers.
%  
%<<
%  exception Scan_failure of string
%>>
%    
%                The exception that formatted input functions raise when the
%               input  cannot be read according to the given format.
%  
%<<
%  val bscanf :
%    Scanning.scanbuf ->
%    ('a, Scanning.scanbuf, 'b) Pervasives.format -> 'a -> 'b
%>>
%    
%                bscanf ib format f reads tokens from the scanning buffer ib
%               according  to the format string format, converts these tokens to
%               values, and  applies the function f to these values.  The result
%               of this application of f is the result of the whole construct.
%               For instance, if p is the function fun s i -> i + 1, then 
%               Scanf.sscanf "x = 1" "%s = %i" p returns 2.
%               Raise Scanf.Scan_failure if the given input does not match the
%               format.
%               Raise Failure if a conversion to a number is not possible.
%               Raise End_of_file if the end of input is encountered while
%               scanning  and the input matches the given format so far.
%               The format is a character string which contains three types of 
%               objects:
%                 
%                - plain characters, which are simply matched with the 
%                  characters of the input, 
%                - conversion specifications, each of which causes reading and 
%                  conversion of one argument for f, 
%                - scanning indications to specify boundaries of tokens. 
%               
%               Among plain characters the space character (ASCII code 32) has a
%                special meaning: it matches --whitespace--, that is any number
%               of tab,  space, newline and carriage return characters. Hence, a
%               space in the format  matches any amount of whitespace in the
%               input.
%               Conversion specifications consist in the % character, followed
%               by  an optional flag, an optional field width, and followed by
%               one or  two conversion characters. The conversion characters and
%               their  meanings are:
%               
%                 
%                - d: reads an optionally signed decimal integer. 
%                - i: reads an optionally signed integer  (usual input formats
%                  for hexadecimal (0x[d]+ and 0X[d]+),  octal (0o[d]+), and
%                  binary 0b[d]+ notations are understood). 
%                - u: reads an unsigned decimal integer. 
%                - x or X: reads an unsigned hexadecimal integer. 
%                - o: reads an unsigned octal integer. 
%                - s: reads a string argument (by default strings end with a
%                  space). 
%                - S: reads a delimited string argument (delimiters and special 
%                  escaped characters follow the lexical conventions of Caml). 
%                - c: reads a single character. To test the current input
%                  character  without reading it, specify a null field width,
%                  i.e. use  specification %0c. Raise Invalid_argument, if the
%                  field width  specification is greater than 1. 
%                - C: reads a single delimited character (delimiters and special
%                   escaped characters follow the lexical conventions of Caml). 
%                - f, e, E, g, G: reads an optionally signed  floating-point
%                  number in decimal notation, in the style dddd.ddd  e/E+-dd. 
%                - F: reads a floating point number according to the lexical 
%                  conventions of Caml (hence the decimal point is mandatory if
%                  the  exponent part is not mentioned). 
%                - B: reads a boolean argument (true or false). 
%                - b: reads a boolean argument (for backward compatibility; do
%                  not use  in new programs). 
%                - ld, li, lu, lx, lX, lo: reads an int32 argument to  the
%                  format specified by the second letter (decimal, hexadecimal,
%                  etc). 
%                - nd, ni, nu, nx, nX, no: reads a nativeint argument to  the
%                  format specified by the second letter. 
%                - Ld, Li, Lu, Lx, LX, Lo: reads an int64 argument to  the
%                  format specified by the second letter. 
%                - [ range ]: reads characters that matches one of the
%                  characters  mentioned in the range of characters range (or
%                  not mentioned in  it, if the range starts with ^). Returns a
%                  string that can be  empty, if no character in the input
%                  matches the range. Hence,  [0-9] returns a string
%                  representing a decimal number or an empty  string if no
%                  decimal digit is found.  If a closing bracket appears in a
%                  range, it must occur as the  first character of the range (or
%                  just after the ^ in case of  range negation); hence []]
%                  matches a ] character and  [^]] matches any character that is
%                  not ]. 
%                - l: applies f to the number of lines read so far. 
%                - n: applies f to the number of characters read so far. 
%                - N: applies f to the number of tokens read so far. 
%                - !: matches the end of input condition. 
%                - %: matches one % character in the input. 
%               
%               Following the % character introducing a conversion, there may be
%                the special flag _: the conversion that follows occurs as
%               usual,  but the resulting value is discarded.
%               The field widths are composed of an optional integer literal 
%               indicating the maximal width of the token to read.  For
%               instance, %6d reads an integer, having at most 6 decimal digits;
%                and %4f reads a float with at most 4 characters.
%               Scanning indications appear just after the string conversions s
%               and  [ range ] to delimit the end of the token. A scanning 
%               indication is introduced by a @ character, followed by some 
%               constant character c. It means that the string token should end 
%               just before the next matching c (which is skipped). If no c 
%               character is encountered, the string token spreads as much as 
%               possible. For instance, "%s@\t" reads a string up to the next 
%               tabulation character. If a scanning indication @c does not 
%               follow a string conversion, it is ignored and treated as a plain
%                c character.
%               Notes:
%               
%                 
%                - the scanning indications introduce slight differences in the 
%                  syntax of Scanf format strings compared to those used by the 
%                  Printf module. However, scanning indications are similar to
%                  those  of the Format module; hence, when producing formatted
%                  text to be  scanned by !Scanf.bscanf, it is wise to use
%                  printing functions  from Format (or, if you need to use
%                  functions from Printf,  banish or carefully double check the
%                  format strings that contain  -@- characters). 
%                
%                 
%                - in addition to relevant digits, -_- characters may appear 
%                  inside numbers (this is reminiscent to the usual Caml 
%                  conventions). If stricter scanning is desired, use the range 
%                  conversion facility instead of the number conversions. 
%                
%                 
%                - the scanf facility is not intended for heavy duty lexical 
%                  analysis and parsing. If it appears not expressive enough for
%                  your  needs, several alternative exists: regular expressions
%                  (module  Str), stream parsers, ocamllex-generated lexers, 
%                  ocamlyacc-generated parsers. 
%  
%<<
%  val fscanf :
%    Pervasives.in_channel ->
%    ('a, Scanning.scanbuf, 'b) Pervasives.format -> 'a -> 'b
%>>
%    
%                Same as Scanf.bscanf[20.27], but inputs from the given channel.
%               Warning: since all scanning functions operate from a scanning 
%               buffer, be aware that each fscanf invocation must allocate a new
%                fresh scanning buffer (unless careful use of partial evaluation
%               in  the program). Hence, there are chances that some characters
%               seem  to be skipped (in fact they are pending in the previously
%               used  buffer). This happens in particular when calling fscanf
%               again  after a scan involving a format that necessitates some
%               look ahead  (such as a format that ends by skipping whitespace
%               in the input).
%               To avoid confusion, consider using bscanf with an explicitly 
%               created scanning buffer. Use for instance Scanning.from_file f 
%               to allocate the scanning buffer reading from file f.
%               This method is not only clearer it is also faster, since
%               scanning  buffers to files are optimized for fast bufferized
%               reading.
%  
%<<
%  val sscanf :
%    string -> ('a, Scanning.scanbuf, 'b) Pervasives.format -> 'a -> 'b
%>>
%    
%                Same as Scanf.bscanf[20.27], but inputs from the given string.
%  
%<<
%  val scanf : ('a, Scanning.scanbuf, 'b) Pervasives.format -> 'a -> 'b
%>>
%    
%                Same as Scanf.bscanf[20.27], but reads from the predefined
%               scanning  buffer Scanf.Scanning.stdib[20.27] that is connected
%               to stdin.
%  
%<<
%  val kscanf :
%    Scanning.scanbuf ->
%    (Scanning.scanbuf -> exn -> 'a) ->
%    ('b, Scanning.scanbuf, 'a) Pervasives.format -> 'b -> 'a
%>>
%    
%                Same as Scanf.bscanf[20.27], but takes an additional function
%               argument  ef that is called in case of error: if the scanning
%               process or  some conversion fails, the scanning function aborts
%               and applies the  error handling function ef to the scanning
%               buffer and the  exception that aborted the scanning process.
%  
%
%
%20.28  Module Set : Sets over ordered types.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  This module implements the set data structure, given a total ordering 
%function over the set elements. All operations over sets  are purely
%applicative (no side-effects).  The implementation uses balanced binary trees,
%and is therefore  reasonably efficient: insertion and membership take time 
%logarithmic in the size of the set, for instance.
%  0.5cm
%<<
%  module type OrderedType = >>
%   
%    sig
% 
%  
%   <<
%     type t 
%   >>
%   
%                   The type of the set elements.
% 
%   <<
%     val compare : t -> t -> int
%   >>
%   
%                   A total ordering function over the set elements.  This is a
%                  two'argument function f such that  f e1 e2 is zero if the
%                  elements e1 and e2 are equal,  f e1 e2 is strictly negative
%                  if e1 is smaller than e2,  and f e1 e2 is strictly positive
%                  if e1 is greater than e2.  Example: a suitable ordering
%                  function is the generic structural  comparison function
%                  Pervasives.compare[19.2].
% 
%  
%  -  end
%  
%                Input signature of the functor Set.Make[20.28].
%  
%<<
%  module type S = >>
%   
%    sig
% 
%  
%   <<
%     type elt 
%   >>
%   
%                   The type of the set elements.
% 
%   <<
%     type t 
%   >>
%   
%                   The type of sets.
% 
%   <<
%     val empty : t
%   >>
%   
%                   The empty set.
% 
%   <<
%     val is_empty : t -> bool
%   >>
%   
%                   Test whether a set is empty or not.
% 
%   <<
%     val mem : elt -> t -> bool
%   >>
%   
%                   mem x s tests whether x belongs to the set s.
% 
%   <<
%     val add : elt -> t -> t
%   >>
%   
%                   add x s returns a set containing all elements of s,  plus x.
%                  If x was already in s, s is returned unchanged.
% 
%   <<
%     val singleton : elt -> t
%   >>
%   
%                   singleton x returns the one-element set containing only x.
% 
%   <<
%     val remove : elt -> t -> t
%   >>
%   
%                   remove x s returns a set containing all elements of s, 
%                  except x. If x was not in s, s is returned unchanged.
% 
%   <<
%     val union : t -> t -> t
%   >>
%   
%                   Set union.
% 
%   <<
%     val inter : t -> t -> t
%   >>
%   
%                   Set intersection.
% 
%   <<
%     val diff : t -> t -> t
%   >>
%   
%                   Set difference.
% 
%   <<
%     val compare : t -> t -> int
%   >>
%   
%                   Total ordering between sets. Can be used as the ordering
%                  function  for doing sets of sets.
% 
%   <<
%     val equal : t -> t -> bool
%   >>
%   
%                   equal s1 s2 tests whether the sets s1 and s2 are  equal,
%                  that is, contain equal elements.
% 
%   <<
%     val subset : t -> t -> bool
%   >>
%   
%                   subset s1 s2 tests whether the set s1 is a subset of  the
%                  set s2.
% 
%   <<
%     val iter : (elt -> unit) -> t -> unit
%   >>
%   
%                   iter f s applies f in turn to all elements of s.  The
%                  elements of s are presented to f in increasing order  with
%                  respect to the ordering over the type of the elements.
% 
%   <<
%     val fold : (elt -> 'a -> 'a) -> t -> 'a -> 'a
%   >>
%   
%                   fold f s a computes (f xN ... (f x2 (f x1 a))...),  where x1
%                  ... xN are the elements of s, in increasing order.
% 
%   <<
%     val for_all : (elt -> bool) -> t -> bool
%   >>
%   
%                   for_all p s checks if all elements of the set  satisfy the
%                  predicate p.
% 
%   <<
%     val exists : (elt -> bool) -> t -> bool
%   >>
%   
%                   exists p s checks if at least one element of  the set
%                  satisfies the predicate p.
% 
%   <<
%     val filter : (elt -> bool) -> t -> t
%   >>
%   
%                   filter p s returns the set of all elements in s  that
%                  satisfy predicate p.
% 
%   <<
%     val partition : (elt -> bool) -> t -> t * t
%   >>
%   
%                   partition p s returns a pair of sets (s1, s2), where  s1 is
%                  the set of all the elements of s that satisfy the  predicate
%                  p, and s2 is the set of all the elements of  s that do not
%                  satisfy p.
% 
%   <<
%     val cardinal : t -> int
%   >>
%   
%                   Return the number of elements of a set.
% 
%   <<
%     val elements : t -> elt list
%   >>
%   
%                   Return the list of all elements of the given set.  The
%                  returned list is sorted in increasing order with respect  to
%                  the ordering Ord.compare, where Ord is the argument  given to
%                  Set.Make[20.28].
% 
%   <<
%     val min_elt : t -> elt
%   >>
%   
%                   Return the smallest element of the given set  (with respect
%                  to the Ord.compare ordering), or raise  Not_found if the set
%                  is empty.
% 
%   <<
%     val max_elt : t -> elt
%   >>
%   
%                   Same as Set.S.min_elt[20.28], but returns the largest
%                  element of the  given set.
% 
%   <<
%     val choose : t -> elt
%   >>
%   
%                   Return one element of the given set, or raise Not_found if 
%                  the set is empty. Which element is chosen is unspecified, 
%                  but equal elements will be chosen for equal sets.
% 
%   <<
%     val split : elt -> t -> t * bool * t
%   >>
%   
%                   split x s returns a triple (l, present, r), where  l is the
%                  set of elements of s that are  strictly less than x;  r is
%                  the set of elements of s that are  strictly greater than x; 
%                  present is false if s contains no element equal to x,  or
%                  true if s contains an element equal to x.
% 
%  
%  -  end
%  
%                Output signature of the functor Set.Make[20.28].
%  
%<<
%  module Make : >>
%   
%  functor (Ord : OrderedType) -> S  with type elt = Ord.t
%                Functor building an implementation of the set structure  given
%               a totally ordered type.
%  
%
%
%20.29  Module Sort : Sorting and merging lists.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%    This module is obsolete and exists only for backward  compatibility.  The
%sorting functions in Array[20.2] and List[20.17] should be used instead.  The
%new functions are faster and use less memory.Sorting and merging lists.
%  0.5cm
%<<
%  val list : ('a -> 'a -> bool) -> 'a list -> 'a list
%>>
%    
%                Sort a list in increasing order according to an ordering
%               predicate.  The predicate should return true if its first
%               argument is  less than or equal to its second argument.
%  
%<<
%  val array : ('a -> 'a -> bool) -> 'a array -> unit
%>>
%    
%                Sort an array in increasing order according to an  ordering
%               predicate.  The predicate should return true if its first
%               argument is  less than or equal to its second argument.  The
%               array is sorted in place.
%  
%<<
%  val merge : ('a -> 'a -> bool) -> 'a list -> 'a list -> 'a list
%>>
%    
%                Merge two lists according to the given predicate.  Assuming the
%               two argument lists are sorted according to the  predicate, merge
%               returns a sorted list containing the elements  from the two
%               lists. The behavior is undefined if the two  argument lists were
%               not sorted.
%  
%
%
%20.30  Module Stack : Last-in first-out stacks.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  This module implements stacks (LIFOs), with in-place modification.
%  0.5cm
%<<
%  type 'a t 
%>>
%    
%                The type of stacks containing elements of type 'a.
%  
%<<
%  exception Empty
%>>
%    
%                Raised when Stack.pop[20.30] or Stack.top[20.30] is applied to
%               an empty stack.
%  
%<<
%  val create : unit -> 'a t
%>>
%    
%                Return a new stack, initially empty.
%  
%<<
%  val push : 'a -> 'a t -> unit
%>>
%    
%                push x s adds the element x at the top of stack s.
%  
%<<
%  val pop : 'a t -> 'a
%>>
%    
%                pop s removes and returns the topmost element in stack s,  or
%               raises Empty if the stack is empty.
%  
%<<
%  val top : 'a t -> 'a
%>>
%    
%                top s returns the topmost element in stack s,  or raises Empty
%               if the stack is empty.
%  
%<<
%  val clear : 'a t -> unit
%>>
%    
%                Discard all elements from a stack.
%  
%<<
%  val copy : 'a t -> 'a t
%>>
%    
%                Return a copy of the given stack.
%  
%<<
%  val is_empty : 'a t -> bool
%>>
%    
%                Return true if the given stack is empty, false otherwise.
%  
%<<
%  val length : 'a t -> int
%>>
%    
%                Return the number of elements in a stack.
%  
%<<
%  val iter : ('a -> unit) -> 'a t -> unit
%>>
%    
%                iter f s applies f in turn to all elements of s,  from the
%               element at the top of the stack to the element at the  bottom of
%               the stack. The stack itself is unchanged.
%  
%
%
%20.31  Module StdLabels : Standard labeled libraries.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  This meta-module provides labelized version of the Array[20.2],  List[20.17]
%and String[20.33] modules.
%  They only differ by their labels. Detailed interfaces can be found  in
%arrayLabels.mli, listLabels.mli and stringLabels.mli.
%  0.5cm
%<<
%  module Array : >>
%   
%    sig
% 
%  
%   <<
%     val length : 'a array -> int
%   >>
%  
%   <<
%     val get : 'a array -> int -> 'a
%   >>
%  
%   <<
%     val set : 'a array -> int -> 'a -> unit
%   >>
%  
%   <<
%     val make : int -> 'a -> 'a array
%   >>
%  
%   <<
%     val create : int -> 'a -> 'a array
%   >>
%  
%   <<
%     val init : int -> f:(int -> 'a) -> 'a array
%   >>
%  
%   <<
%     val make_matrix : dimx:int -> dimy:int -> 'a -> 'a array array
%   >>
%  
%   <<
%     val create_matrix : dimx:int -> dimy:int -> 'a -> 'a array array
%   >>
%  
%   <<
%     val append : 'a array -> 'a array -> 'a array
%   >>
%  
%   <<
%     val concat : 'a array list -> 'a array
%   >>
%  
%   <<
%     val sub : 'a array -> pos:int -> len:int -> 'a array
%   >>
%  
%   <<
%     val copy : 'a array -> 'a array
%   >>
%  
%   <<
%     val fill : 'a array -> pos:int -> len:int -> 'a -> unit
%   >>
%  
%   <<
%     val blit :
%       src:'a array -> src_pos:int -> dst:'a array -> dst_pos:int -> len:int ->
%   unit
%   >>
%  
%   <<
%     val to_list : 'a array -> 'a list
%   >>
%  
%   <<
%     val of_list : 'a list -> 'a array
%   >>
%  
%   <<
%     val iter : f:('a -> unit) -> 'a array -> unit
%   >>
%  
%   <<
%     val map : f:('a -> 'b) -> 'a array -> 'b array
%   >>
%  
%   <<
%     val iteri : f:(int -> 'a -> unit) -> 'a array -> unit
%   >>
%  
%   <<
%     val mapi : f:(int -> 'a -> 'b) -> 'a array -> 'b array
%   >>
%  
%   <<
%     val fold_left : f:('a -> 'b -> 'a) -> init:'a -> 'b array -> 'a
%   >>
%  
%   <<
%     val fold_right : f:('a -> 'b -> 'b) -> 'a array -> init:'b -> 'b
%   >>
%  
%   <<
%     val sort : cmp:('a -> 'a -> int) -> 'a array -> unit
%   >>
%  
%   <<
%     val stable_sort : cmp:('a -> 'a -> int) -> 'a array -> unit
%   >>
%  
%   <<
%     val fast_sort : cmp:('a -> 'a -> int) -> 'a array -> unit
%   >>
%  
%   <<
%     val unsafe_get : 'a array -> int -> 'a
%   >>
%  
%   <<
%     val unsafe_set : 'a array -> int -> 'a -> unit
%   >>
%   
%  -  end
%  
%<<
%  module List : >>
%   
%    sig
% 
%  
%   <<
%     val length : 'a list -> int
%   >>
%  
%   <<
%     val hd : 'a list -> 'a
%   >>
%  
%   <<
%     val tl : 'a list -> 'a list
%   >>
%  
%   <<
%     val nth : 'a list -> int -> 'a
%   >>
%  
%   <<
%     val rev : 'a list -> 'a list
%   >>
%  
%   <<
%     val append : 'a list -> 'a list -> 'a list
%   >>
%  
%   <<
%     val rev_append : 'a list -> 'a list -> 'a list
%   >>
%  
%   <<
%     val concat : 'a list list -> 'a list
%   >>
%  
%   <<
%     val flatten : 'a list list -> 'a list
%   >>
%  
%   <<
%     val iter : f:('a -> unit) -> 'a list -> unit
%   >>
%  
%   <<
%     val map : f:('a -> 'b) -> 'a list -> 'b list
%   >>
%  
%   <<
%     val rev_map : f:('a -> 'b) -> 'a list -> 'b list
%   >>
%  
%   <<
%     val fold_left : f:('a -> 'b -> 'a) -> init:'a -> 'b list -> 'a
%   >>
%  
%   <<
%     val fold_right : f:('a -> 'b -> 'b) -> 'a list -> init:'b -> 'b
%   >>
%  
%   <<
%     val iter2 : f:('a -> 'b -> unit) -> 'a list -> 'b list -> unit
%   >>
%  
%   <<
%     val map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
%   >>
%  
%   <<
%     val rev_map2 : f:('a -> 'b -> 'c) -> 'a list -> 'b list -> 'c list
%   >>
%  
%   <<
%     val fold_left2 :
%       f:('a -> 'b -> 'c -> 'a) -> init:'a -> 'b list -> 'c list -> 'a
%   >>
%  
%   <<
%     val fold_right2 :
%       f:('a -> 'b -> 'c -> 'c) -> 'a list -> 'b list -> init:'c -> 'c
%   >>
%  
%   <<
%     val for_all : f:('a -> bool) -> 'a list -> bool
%   >>
%  
%   <<
%     val exists : f:('a -> bool) -> 'a list -> bool
%   >>
%  
%   <<
%     val for_all2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
%   >>
%  
%   <<
%     val exists2 : f:('a -> 'b -> bool) -> 'a list -> 'b list -> bool
%   >>
%  
%   <<
%     val mem : 'a -> set:'a list -> bool
%   >>
%  
%   <<
%     val memq : 'a -> set:'a list -> bool
%   >>
%  
%   <<
%     val find : f:('a -> bool) -> 'a list -> 'a
%   >>
%  
%   <<
%     val filter : f:('a -> bool) -> 'a list -> 'a list
%   >>
%  
%   <<
%     val find_all : f:('a -> bool) -> 'a list -> 'a list
%   >>
%  
%   <<
%     val partition : f:('a -> bool) -> 'a list -> 'a list * 'a list
%   >>
%  
%   <<
%     val assoc : 'a -> ('a * 'b) list -> 'b
%   >>
%  
%   <<
%     val assq : 'a -> ('a * 'b) list -> 'b
%   >>
%  
%   <<
%     val mem_assoc : 'a -> map:('a * 'b) list -> bool
%   >>
%  
%   <<
%     val mem_assq : 'a -> map:('a * 'b) list -> bool
%   >>
%  
%   <<
%     val remove_assoc : 'a -> ('a * 'b) list -> ('a * 'b) list
%   >>
%  
%   <<
%     val remove_assq : 'a -> ('a * 'b) list -> ('a * 'b) list
%   >>
%  
%   <<
%     val split : ('a * 'b) list -> 'a list * 'b list
%   >>
%  
%   <<
%     val combine : 'a list -> 'b list -> ('a * 'b) list
%   >>
%  
%   <<
%     val sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
%   >>
%  
%   <<
%     val stable_sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
%   >>
%  
%   <<
%     val fast_sort : cmp:('a -> 'a -> int) -> 'a list -> 'a list
%   >>
%  
%   <<
%     val merge : cmp:('a -> 'a -> int) -> 'a list -> 'a list -> 'a list
%   >>
%   
%  -  end
%  
%<<
%  module String : >>
%   
%    sig
% 
%  
%   <<
%     val length : string -> int
%   >>
%  
%   <<
%     val get : string -> int -> char
%   >>
%  
%   <<
%     val set : string -> int -> char -> unit
%   >>
%  
%   <<
%     val create : int -> string
%   >>
%  
%   <<
%     val make : int -> char -> string
%   >>
%  
%   <<
%     val copy : string -> string
%   >>
%  
%   <<
%     val sub : string -> pos:int -> len:int -> string
%   >>
%  
%   <<
%     val fill : string -> pos:int -> len:int -> char -> unit
%   >>
%  
%   <<
%     val blit :
%       src:string -> src_pos:int -> dst:string -> dst_pos:int -> len:int ->
%   unit
%   >>
%  
%   <<
%     val concat : sep:string -> string list -> string
%   >>
%  
%   <<
%     val iter : f:(char -> unit) -> string -> unit
%   >>
%  
%   <<
%     val escaped : string -> string
%   >>
%  
%   <<
%     val index : string -> char -> int
%   >>
%  
%   <<
%     val rindex : string -> char -> int
%   >>
%  
%   <<
%     val index_from : string -> int -> char -> int
%   >>
%  
%   <<
%     val rindex_from : string -> int -> char -> int
%   >>
%  
%   <<
%     val contains : string -> char -> bool
%   >>
%  
%   <<
%     val contains_from : string -> int -> char -> bool
%   >>
%  
%   <<
%     val rcontains_from : string -> int -> char -> bool
%   >>
%  
%   <<
%     val uppercase : string -> string
%   >>
%  
%   <<
%     val lowercase : string -> string
%   >>
%  
%   <<
%     val capitalize : string -> string
%   >>
%  
%   <<
%     val uncapitalize : string -> string
%   >>
%  
%   <<
%     type t = string 
%   >>
%  
%   <<
%     val compare : t -> t -> int
%   >>
%  
%   <<
%     val unsafe_get : string -> int -> char
%   >>
%  
%   <<
%     val unsafe_set : string -> int -> char -> unit
%   >>
%  
%   <<
%     val unsafe_blit :
%       src:string -> src_pos:int -> dst:string -> dst_pos:int -> len:int ->
%   unit
%   >>
%  
%   <<
%     val unsafe_fill : string -> pos:int -> len:int -> char -> unit
%   >>
%   
%  -  end
%  
%
%
%20.32  Module Stream : Streams and parsers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%<<
%  type 'a t 
%>>
%    
%                The type of streams holding values of type 'a.
%  
%<<
%  exception Failure
%>>
%    
%                Raised by parsers when none of the first components of the
%               stream  patterns is accepted.
%  
%<<
%  exception Error of string
%>>
%    
%                Raised by parsers when the first component of a stream pattern
%               is  accepted, but one of the following components is rejected.
%  
%
%Stream builders
%===============
%  
%  Warning: these functions create streams with fast access; it is illegal  to
%mix them with streams built with [< >]; would raise Failure  when accessing
%such mixed streams.
%<<
%  val from : (int -> 'a option) -> 'a t
%>>
%    
%                Stream.from f returns a stream built from the function f.  To
%               create a new stream element, the function f is called with  the
%               current stream count. The user function f must return either 
%               Some <value> for a value or None to specify the end of the 
%               stream.
%  
%<<
%  val of_list : 'a list -> 'a t
%>>
%    
%                Return the stream holding the elements of the list in the same 
%               order.
%  
%<<
%  val of_string : string -> char t
%>>
%    
%                Return the stream of the characters of the string parameter.
%  
%<<
%  val of_channel : Pervasives.in_channel -> char t
%>>
%    
%                Return the stream of the characters read from the input
%               channel.
%  
%
%Stream iterator
%===============
%  
%<<
%  val iter : ('a -> unit) -> 'a t -> unit
%>>
%    
%                Stream.iter f s scans the whole stream s, applying function f 
%               in turn to each stream element encountered.
%  
%
%Predefined parsers
%==================
%  
%<<
%  val next : 'a t -> 'a
%>>
%    
%                Return the first element of the stream and remove it from the 
%               stream. Raise Stream.Failure if the stream is empty.
%  
%<<
%  val empty : 'a t -> unit
%>>
%    
%                Return () if the stream is empty, else raise Stream.Failure.
%  
%
%Useful functions
%================
%  
%<<
%  val peek : 'a t -> 'a option
%>>
%    
%                Return Some of "the first element" of the stream, or None if 
%               the stream is empty.
%  
%<<
%  val junk : 'a t -> unit
%>>
%    
%                Remove the first element of the stream, possibly unfreezing  it
%               before.
%  
%<<
%  val count : 'a t -> int
%>>
%    
%                Return the current count of the stream elements, i.e. the
%               number  of the stream elements discarded.
%  
%<<
%  val npeek : int -> 'a t -> 'a list
%>>
%    
%                npeek n returns the list of the n first elements of  the
%               stream, or all its remaining elements if less than n  elements
%               are available.
%  
%
%
%20.33  Module String : String operations.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%<<
%  val length : string -> int
%>>
%    
%                Return the length (number of characters) of the given string.
%  
%<<
%  val get : string -> int -> char
%>>
%    
%                String.get s n returns character number n in string s.  The
%               first character is character number 0.  The last character is
%               character number String.length s - 1.  You can also write s.[n]
%               instead of String.get s n.
%               Raise Invalid_argument "index out of bounds"  if n is outside
%               the range 0 to (String.length s - 1).
%  
%<<
%  val set : string -> int -> char -> unit
%>>
%    
%                String.set s n c modifies string s in place,  replacing the
%               character number n by c.  You can also write s.[n] <- c instead
%               of String.set s n c.  Raise Invalid_argument "index out of
%               bounds"  if n is outside the range 0 to (String.length s - 1).
%  
%<<
%  val create : int -> string
%>>
%    
%                String.create n returns a fresh string of length n.  The string
%               initially contains arbitrary characters.  Raise Invalid_argument
%               if n < 0 or n > Sys.max_string_length.
%  
%<<
%  val make : int -> char -> string
%>>
%    
%                String.make n c returns a fresh string of length n,  filled
%               with the character c.  Raise Invalid_argument if n < 0 or n >
%               Sys.max_string_length[20.34].
%  
%<<
%  val copy : string -> string
%>>
%    
%                Return a copy of the given string.
%  
%<<
%  val sub : string -> int -> int -> string
%>>
%    
%                String.sub s start len returns a fresh string of length len, 
%               containing the characters number start to start + len - 1  of
%               string s.  Raise Invalid_argument if start and len do not 
%               designate a valid substring of s; that is, if start < 0,  or len
%               < 0, or start + len > String.length[20.33] s.
%  
%<<
%  val fill : string -> int -> int -> char -> unit
%>>
%    
%                String.fill s start len c modifies string s in place, 
%               replacing the characters number start to start + len - 1  by c. 
%               Raise Invalid_argument if start and len do not  designate a
%               valid substring of s.
%  
%<<
%  val blit : string -> int -> string -> int -> int -> unit
%>>
%    
%                String.blit src srcoff dst dstoff len copies len characters 
%               from string src, starting at character number srcoff, to  string
%               dst, starting at character number dstoff. It works  correctly
%               even if src and dst are the same string,  and the source and
%               destination chunks overlap.  Raise Invalid_argument if srcoff
%               and len do not  designate a valid substring of src, or if dstoff
%               and len  do not designate a valid substring of dst.
%  
%<<
%  val concat : string -> string list -> string
%>>
%    
%                String.concat sep sl concatenates the list of strings sl, 
%               inserting the separator string sep between each.
%  
%<<
%  val iter : (char -> unit) -> string -> unit
%>>
%    
%                String.iter f s applies function f in turn to all  the
%               characters of s. It is equivalent to  f s.[0]; f s.[1]; ...; f
%               s.[String.length s - 1]; ().
%  
%<<
%  val escaped : string -> string
%>>
%    
%                Return a copy of the argument, with special characters 
%               represented by escape sequences, following the lexical 
%               conventions of Objective Caml. If there is no special  character
%               in the argument, return the original string itself,  not a copy.
%  
%<<
%  val index : string -> char -> int
%>>
%    
%                String.index s c returns the position of the leftmost 
%               occurrence of character c in string s.  Raise Not_found if c
%               does not occur in s.
%  
%<<
%  val rindex : string -> char -> int
%>>
%    
%                String.rindex s c returns the position of the rightmost 
%               occurrence of character c in string s.  Raise Not_found if c
%               does not occur in s.
%  
%<<
%  val index_from : string -> int -> char -> int
%>>
%    
%                Same as String.index[20.33], but start  searching at the
%               character position given as second argument.  String.index s c
%               is equivalent to String.index_from s 0 c.
%  
%<<
%  val rindex_from : string -> int -> char -> int
%>>
%    
%                Same as String.rindex[20.33], but start  searching at the
%               character position given as second argument.  String.rindex s c
%               is equivalent to  String.rindex_from s (String.length s - 1) c.
%  
%<<
%  val contains : string -> char -> bool
%>>
%    
%                String.contains s c tests if character c  appears in the string
%               s.
%  
%<<
%  val contains_from : string -> int -> char -> bool
%>>
%    
%                String.contains_from s start c tests if character c  appears in
%               the substring of s starting from start to the end  of s.  Raise
%               Invalid_argument if start is not a valid index of s.
%  
%<<
%  val rcontains_from : string -> int -> char -> bool
%>>
%    
%                String.rcontains_from s stop c tests if character c  appears in
%               the substring of s starting from the beginning  of s to index
%               stop.  Raise Invalid_argument if stop is not a valid index of s.
%  
%<<
%  val uppercase : string -> string
%>>
%    
%                Return a copy of the argument, with all lowercase letters 
%               translated to uppercase, including accented letters of the ISO 
%               Latin-1 (8859-1) character set.
%  
%<<
%  val lowercase : string -> string
%>>
%    
%                Return a copy of the argument, with all uppercase letters 
%               translated to lowercase, including accented letters of the ISO 
%               Latin-1 (8859-1) character set.
%  
%<<
%  val capitalize : string -> string
%>>
%    
%                Return a copy of the argument, with the first character set to
%               uppercase.
%  
%<<
%  val uncapitalize : string -> string
%>>
%    
%                Return a copy of the argument, with the first character set to
%               lowercase.
%  
%<<
%  type t = string 
%>>
%    
%                An alias for the type of strings.
%  
%<<
%  val compare : t -> t -> int
%>>
%    
%                The comparison function for strings, with the same
%               specification as  Pervasives.compare[19.2]. Along with the type
%               t, this function compare  allows the module String to be passed
%               as argument to the functors  Set.Make[20.28] and
%               Map.Make[20.18].
%  
%
%
%20.34  Module Sys : System interface.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%<<
%  val argv : string array
%>>
%    
%                The command line arguments given to the process.  The first
%               element is the command name used to invoke the program.  The
%               following elements are the command-line arguments  given to the
%               program.
%  
%<<
%  val executable_name : string
%>>
%    
%                The name of the file containing the executable currently
%               running.
%  
%<<
%  val file_exists : string -> bool
%>>
%    
%                Test if a file with the given name exists.
%  
%<<
%  val remove : string -> unit
%>>
%    
%                Remove the given file name from the file system.
%  
%<<
%  val rename : string -> string -> unit
%>>
%    
%                Rename a file. The first argument is the old name and the 
%               second is the new name. If there is already another file  under
%               the new name, rename may replace it, or raise an  exception,
%               depending on your operating system.
%  
%<<
%  val getenv : string -> string
%>>
%    
%                Return the value associated to a variable in the process 
%               environment. Raise Not_found if the variable is unbound.
%  
%<<
%  val command : string -> int
%>>
%    
%                Execute the given shell command and return its exit code.
%  
%<<
%  val time : unit -> float
%>>
%    
%                Return the processor time, in seconds, used by the program 
%               since the beginning of execution.
%  
%<<
%  val chdir : string -> unit
%>>
%    
%                Change the current working directory of the process.
%  
%<<
%  val getcwd : unit -> string
%>>
%    
%                Return the current working directory of the process.
%  
%<<
%  val readdir : string -> string array
%>>
%    
%                Return the names of all files present in the given directory. 
%               Names denoting the current directory and the parent directory 
%               ("." and ".." in Unix) are not returned. Each string in the 
%               result is a file name rather than a complete path. There is no 
%               guarantee that the name strings in the resulting array will
%               appear  in any specific order; they are not, in particular,
%               guaranteed to  appear in alphabetical order.
%  
%<<
%  val interactive : bool Pervasives.ref
%>>
%    
%                This reference is initially set to false in standalone 
%               programs and to true if the code is being executed under  the
%               interactive toplevel system ocaml.
%  
%<<
%  val os_type : string
%>>
%    
%                Operating system currently executing the Caml program. One of
%                 
%                - "Unix" (for all Unix versions, including Linux and Mac OS X),
%                  
%                - "Win32" (for MS-Windows, OCaml compiled with MSVC++ or
%                  Mingw), 
%                - "Cygwin" (for MS-Windows, OCaml compiled with Cygwin). 
%  
%<<
%  val word_size : int
%>>
%    
%                Size of one word on the machine currently executing the Caml 
%               program, in bits: 32 or 64.
%  
%<<
%  val max_string_length : int
%>>
%    
%                Maximum length of a string.
%  
%<<
%  val max_array_length : int
%>>
%    
%                Maximum length of a normal array. The maximum length of a float
%                array is max_array_length/2 on 32'bit machines and 
%               max_array_length on 64'bit machines.
%  
%
%Signal handling
%===============
%  
%<<
%  type signal_behavior =
%    | Signal_default
%    | Signal_ignore
%    | Signal_handle of (int -> unit)
%>>
%   
%                What to do when receiving a signal:
%                 
%                - Signal_default: take the default behavior  (usually: abort
%                  the program) 
%                - Signal_ignore: ignore the signal 
%                - Signal_handle f: call function f, giving it the signal 
%                  number as argument. 
%  
%   
%<<
%  val signal : int -> signal_behavior -> signal_behavior
%>>
%    
%                Set the behavior of the system on receipt of a given signal.
%               The  first argument is the signal number. Return the behavior 
%               previously associated with the signal. If the signal number is 
%               invalid (or not available on your system), an Invalid_argument 
%               exception is raised.
%  
%<<
%  val set_signal : int -> signal_behavior -> unit
%>>
%    
%                Same as Sys.signal[20.34] but return value is ignored.
%  
%
%Signal numbers for the standard POSIX signals.
%----------------------------------------------
%  
%<<
%  val sigabrt : int
%>>
%    
%                Abnormal termination
%  
%<<
%  val sigalrm : int
%>>
%    
%                Timeout
%  
%<<
%  val sigfpe : int
%>>
%    
%                Arithmetic exception
%  
%<<
%  val sighup : int
%>>
%    
%                Hangup on controlling terminal
%  
%<<
%  val sigill : int
%>>
%    
%                Invalid hardware instruction
%  
%<<
%  val sigint : int
%>>
%    
%                Interactive interrupt (ctrl'c)
%  
%<<
%  val sigkill : int
%>>
%    
%                Termination (cannot be ignored)
%  
%<<
%  val sigpipe : int
%>>
%    
%                Broken pipe
%  
%<<
%  val sigquit : int
%>>
%    
%                Interactive termination
%  
%<<
%  val sigsegv : int
%>>
%    
%                Invalid memory reference
%  
%<<
%  val sigterm : int
%>>
%    
%                Termination
%  
%<<
%  val sigusr1 : int
%>>
%    
%                Application-defined signal 1
%  
%<<
%  val sigusr2 : int
%>>
%    
%                Application-defined signal 2
%  
%<<
%  val sigchld : int
%>>
%    
%                Child process terminated
%  
%<<
%  val sigcont : int
%>>
%    
%                Continue
%  
%<<
%  val sigstop : int
%>>
%    
%                Stop
%  
%<<
%  val sigtstp : int
%>>
%    
%                Interactive stop
%  
%<<
%  val sigttin : int
%>>
%    
%                Terminal read from background process
%  
%<<
%  val sigttou : int
%>>
%    
%                Terminal write from background process
%  
%<<
%  val sigvtalrm : int
%>>
%    
%                Timeout in virtual time
%  
%<<
%  val sigprof : int
%>>
%    
%                Profiling interrupt
%  
%<<
%  exception Break
%>>
%    
%                Exception raised on interactive interrupt if
%               Sys.catch_break[20.34]  is on.
%  
%<<
%  val catch_break : bool -> unit
%>>
%    
%                catch_break governs whether interactive interrupt (ctrl'c) 
%               terminates the program or raises the Break exception.   Call
%               catch_break true to enable raising Break,  and catch_break false
%               to let the system  terminate the program on user interrupt.
%  
%<<
%  val ocaml_version : string
%>>
%    
%                ocaml_version is the version of Objective Caml.  It is a string
%               of the form "major.minor[.patchlevel][+additional-info]"  Where
%               major, minor, and patchlevel are integers, and  additional-info
%               is an arbitrary string. The [.patchlevel] and 
%               [+additional-info] parts may be absent.
%  
%
%
%20.35  Module Weak : Arrays of weak pointers and hash tables of weak pointers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%
%Low-level functions
%===================
%  
%<<
%  type 'a t 
%>>
%    
%                The type of arrays of weak pointers (weak arrays). A weak 
%               pointer is a value that the garbage collector may erase at  any
%               time.  A weak pointer is said to be full if it points to a
%               value,  empty if the value was erased by the GC.  Note that weak
%               arrays cannot be marshaled using  Pervasives.output_value[19.2]
%               or the functions of the Marshal[20.19]  module.
%  
%<<
%  val create : int -> 'a t
%>>
%    
%                Weak.create n returns a new weak array of length n.  All the
%               pointers are initially empty. Raise Invalid_argument  if n is
%               negative or greater than Sys.max_array_length[20.34]-1.
%  
%<<
%  val length : 'a t -> int
%>>
%    
%                Weak.length ar returns the length (number of elements) of  ar.
%  
%<<
%  val set : 'a t -> int -> 'a option -> unit
%>>
%    
%                Weak.set ar n (Some el) sets the nth cell of ar to be a  (full)
%               pointer to el; Weak.set ar n None sets the nth  cell of ar to
%               empty.  Raise Invalid_argument "Weak.set" if n is not in the
%               range  0 to Weak.length[20.35] a - 1.
%  
%<<
%  val get : 'a t -> int -> 'a option
%>>
%    
%                Weak.get ar n returns None if the nth cell of ar is  empty,
%               Some x (where x is the value) if it is full.  Raise
%               Invalid_argument "Weak.get" if n is not in the range  0 to
%               Weak.length[20.35] a - 1.
%  
%<<
%  val get_copy : 'a t -> int -> 'a option
%>>
%    
%                Weak.get_copy ar n returns None if the nth cell of ar is 
%               empty, Some x (where x is a (shallow) copy of the value) if  it
%               is full.  In addition to pitfalls with mutable values, the
%               interesting  difference with get is that get_copy does not
%               prevent  the incremental GC from erasing the value in its
%               current cycle  (get may delay the erasure to the next GC cycle).
%                Raise Invalid_argument "Weak.get" if n is not in the range  0
%               to Weak.length[20.35] a - 1.
%  
%<<
%  val check : 'a t -> int -> bool
%>>
%    
%                Weak.check ar n returns true if the nth cell of ar is  full,
%               false if it is empty. Note that even if Weak.check ar n  returns
%               true, a subsequent Weak.get[20.35] ar n can return None.
%  
%<<
%  val fill : 'a t -> int -> int -> 'a option -> unit
%>>
%    
%                Weak.fill ar ofs len el sets to el all pointers of ar from  ofs
%               to ofs + len - 1. Raise Invalid_argument "Weak.fill"  if ofs and
%               len do not designate a valid subarray of a.
%  
%<<
%  val blit : 'a t -> int -> 'a t -> int -> int -> unit
%>>
%    
%                Weak.blit ar1 off1 ar2 off2 len copies len weak pointers  from
%               ar1 (starting at off1) to ar2 (starting at off2).  It works
%               correctly even if ar1 and ar2 are the same.  Raise
%               Invalid_argument "Weak.blit" if off1 and len do  not designate a
%               valid subarray of ar1, or if off2 and len  do not designate a
%               valid subarray of ar2.
%  
%
%Weak hash tables
%================
%  
%  A weak hash table is a hashed set of values. Each value may  magically
%disappear from the set when it is not used by the  rest of the program any
%more. This is normally used to share  data structures without inducing memory
%leaks.  Weak hash tables are defined on values from a Hashtbl.HashedType[20.12]
% module; the equal relation and hash function are taken from that  module. We
%will say that v is an instance of x if equal x v  is true.
%  The equal relation must be able to work on a shallow copy of  the values and
%give the same result as with the values themselves.
%<<
%  module type S = >>
%   
%    sig
% 
%  
%   <<
%     type data 
%   >>
%   
%                   The type of the elements stored in the table.
% 
%   <<
%     type t 
%   >>
%   
%                   The type of tables that contain elements of type data.  Note
%                  that weak hash tables cannot be marshaled using 
%                  Pervasives.output_value[19.2] or the functions of the
%                  Marshal[20.19]  module.
% 
%   <<
%     val create : int -> t
%   >>
%   
%                   create n creates a new empty weak hash table, of initial 
%                  size n. The table will grow as needed.
% 
%   <<
%     val clear : t -> unit
%   >>
%   
%                   Remove all elements from the table.
% 
%   <<
%     val merge : t -> data -> data
%   >>
%   
%                   merge t x returns an instance of x found in t if any,  or
%                  else adds x to t and return x.
% 
%   <<
%     val add : t -> data -> unit
%   >>
%   
%                   add t x adds x to t. If there is already an instance  of x
%                  in t, it is unspecified which one will be  returned by
%                  subsequent calls to find and merge.
% 
%   <<
%     val remove : t -> data -> unit
%   >>
%   
%                   remove t x removes from t one instance of x. Does  nothing
%                  if there is no instance of x in t.
% 
%   <<
%     val find : t -> data -> data
%   >>
%   
%                   find t x returns an instance of x found in t.  Raise
%                  Not_found if there is no such element.
% 
%   <<
%     val find_all : t -> data -> data list
%   >>
%   
%                   find_all t x returns a list of all the instances of x  found
%                  in t.
% 
%   <<
%     val mem : t -> data -> bool
%   >>
%   
%                   mem t x returns true if there is at least one instance  of x
%                  in t, false otherwise.
% 
%   <<
%     val iter : (data -> unit) -> t -> unit
%   >>
%   
%                   iter f t calls f on each element of t, in some unspecified 
%                  order. It is not specified what happens if f tries to change 
%                  t itself.
% 
%   <<
%     val fold : (data -> 'a -> 'a) -> t -> 'a -> 'a
%   >>
%   
%                   fold f t init computes (f d1 (... (f dN init))) where  d1
%                  ... dN are the elements of t in some unspecified order.  It
%                  is not specified what happens if f tries to change t  itself.
% 
%   <<
%     val count : t -> int
%   >>
%   
%                   Count the number of elements in the table. count t gives the
%                   same result as fold (fun _ n -> n+1) t 0 but does not delay
%                  the  deallocation of the dead elements.
% 
%   <<
%     val stats : t -> int * int * int * int * int * int
%   >>
%   
%                   Return statistics on the table. The numbers are, in order: 
%                  table length, number of entries, sum of bucket lengths, 
%                  smallest bucket length, median bucket length, biggest bucket
%                  length.
% 
%  
%  -  end
%  
%                The output signature of the functor Weak.Make[20.35].
%  
%<<
%  module Make : >>
%   
%  functor (H : Hashtbl.HashedType) -> S  with type data = H.t
%                Functor building an implementation of the weak hash table
%               structure.
%  
%    
%  
%
%Chapter 21    The unix library: Unix system calls
%*************************************************
%   
%  The unix library makes many Unix system calls and system-related library
%functions available to Objective Caml programs. This chapter describes briefly
%the functions provided. Refer to sections 2 and 3 of the Unix manual for more
%details on the behavior of these functions.
%  Not all functions are provided by all Unix variants. If some functions are
%not available, they will raise Invalid_arg when called.
%  Programs that use the unix library must be linked as follows: 
%<<
%          ocamlc other options unix.cma other files
%          ocamlopt other options unix.cmxa other files
%>>
%   For interactive use of the unix library, do: 
%<<
%          ocamlmktop -o mytop unix.cma
%          ./mytop
%>>
%   or (if dynamic linking of C libraries is supported on your platform), start
%ocaml and type #load "unix.cma";;.
%     Windows: 
%                A fairly complete emulation of the Unix system calls is
%               provided in the Windows version of Objective Caml. The end of
%               this chapter gives more information on the functions that are
%               not supported under Windows. 
%  
%  
%
%21.1  Module Unix : Interface to the Unix system
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%
%Error report
%============
%  
%<<
%  type error =
%    | E2BIG
%>>
%   
%                Argument list too long 
%   
%<<
%    | EACCES
%>>
%   
%                Permission denied 
%   
%<<
%    | EAGAIN
%>>
%   
%                Resource temporarily unavailable; try again 
%   
%<<
%    | EBADF
%>>
%   
%                Bad file descriptor 
%   
%<<
%    | EBUSY
%>>
%   
%                Resource unavailable 
%   
%<<
%    | ECHILD
%>>
%   
%                No child process 
%   
%<<
%    | EDEADLK
%>>
%   
%                Resource deadlock would occur 
%   
%<<
%    | EDOM
%>>
%   
%                Domain error for math functions, etc. 
%   
%<<
%    | EEXIST
%>>
%   
%                File exists 
%   
%<<
%    | EFAULT
%>>
%   
%                Bad address 
%   
%<<
%    | EFBIG
%>>
%   
%                File too large 
%   
%<<
%    | EINTR
%>>
%   
%                Function interrupted by signal 
%   
%<<
%    | EINVAL
%>>
%   
%                Invalid argument 
%   
%<<
%    | EIO
%>>
%   
%                Hardware I/O error 
%   
%<<
%    | EISDIR
%>>
%   
%                Is a directory 
%   
%<<
%    | EMFILE
%>>
%   
%                Too many open files by the process 
%   
%<<
%    | EMLINK
%>>
%   
%                Too many links 
%   
%<<
%    | ENAMETOOLONG
%>>
%   
%                Filename too long 
%   
%<<
%    | ENFILE
%>>
%   
%                Too many open files in the system 
%   
%<<
%    | ENODEV
%>>
%   
%                No such device 
%   
%<<
%    | ENOENT
%>>
%   
%                No such file or directory 
%   
%<<
%    | ENOEXEC
%>>
%   
%                Not an executable file 
%   
%<<
%    | ENOLCK
%>>
%   
%                No locks available 
%   
%<<
%    | ENOMEM
%>>
%   
%                Not enough memory 
%   
%<<
%    | ENOSPC
%>>
%   
%                No space left on device 
%   
%<<
%    | ENOSYS
%>>
%   
%                Function not supported 
%   
%<<
%    | ENOTDIR
%>>
%   
%                Not a directory 
%   
%<<
%    | ENOTEMPTY
%>>
%   
%                Directory not empty 
%   
%<<
%    | ENOTTY
%>>
%   
%                Inappropriate I/O control operation 
%   
%<<
%    | ENXIO
%>>
%   
%                No such device or address 
%   
%<<
%    | EPERM
%>>
%   
%                Operation not permitted 
%   
%<<
%    | EPIPE
%>>
%   
%                Broken pipe 
%   
%<<
%    | ERANGE
%>>
%   
%                Result too large 
%   
%<<
%    | EROFS
%>>
%   
%                Read-only file system 
%   
%<<
%    | ESPIPE
%>>
%   
%                Invalid seek e.g. on a pipe 
%   
%<<
%    | ESRCH
%>>
%   
%                No such process 
%   
%<<
%    | EXDEV
%>>
%   
%                Invalid link 
%   
%<<
%    | EWOULDBLOCK
%>>
%   
%                Operation would block 
%   
%<<
%    | EINPROGRESS
%>>
%   
%                Operation now in progress 
%   
%<<
%    | EALREADY
%>>
%   
%                Operation already in progress 
%   
%<<
%    | ENOTSOCK
%>>
%   
%                Socket operation on non-socket 
%   
%<<
%    | EDESTADDRREQ
%>>
%   
%                Destination address required 
%   
%<<
%    | EMSGSIZE
%>>
%   
%                Message too long 
%   
%<<
%    | EPROTOTYPE
%>>
%   
%                Protocol wrong type for socket 
%   
%<<
%    | ENOPROTOOPT
%>>
%   
%                Protocol not available 
%   
%<<
%    | EPROTONOSUPPORT
%>>
%   
%                Protocol not supported 
%   
%<<
%    | ESOCKTNOSUPPORT
%>>
%   
%                Socket type not supported 
%   
%<<
%    | EOPNOTSUPP
%>>
%   
%                Operation not supported on socket 
%   
%<<
%    | EPFNOSUPPORT
%>>
%   
%                Protocol family not supported 
%   
%<<
%    | EAFNOSUPPORT
%>>
%   
%                Address family not supported by protocol family 
%   
%<<
%    | EADDRINUSE
%>>
%   
%                Address already in use 
%   
%<<
%    | EADDRNOTAVAIL
%>>
%   
%                Can-t assign requested address 
%   
%<<
%    | ENETDOWN
%>>
%   
%                Network is down 
%   
%<<
%    | ENETUNREACH
%>>
%   
%                Network is unreachable 
%   
%<<
%    | ENETRESET
%>>
%   
%                Network dropped connection on reset 
%   
%<<
%    | ECONNABORTED
%>>
%   
%                Software caused connection abort 
%   
%<<
%    | ECONNRESET
%>>
%   
%                Connection reset by peer 
%   
%<<
%    | ENOBUFS
%>>
%   
%                No buffer space available 
%   
%<<
%    | EISCONN
%>>
%   
%                Socket is already connected 
%   
%<<
%    | ENOTCONN
%>>
%   
%                Socket is not connected 
%   
%<<
%    | ESHUTDOWN
%>>
%   
%                Can-t send after socket shutdown 
%   
%<<
%    | ETOOMANYREFS
%>>
%   
%                Too many references: can-t splice 
%   
%<<
%    | ETIMEDOUT
%>>
%   
%                Connection timed out 
%   
%<<
%    | ECONNREFUSED
%>>
%   
%                Connection refused 
%   
%<<
%    | EHOSTDOWN
%>>
%   
%                Host is down 
%   
%<<
%    | EHOSTUNREACH
%>>
%   
%                No route to host 
%   
%<<
%    | ELOOP
%>>
%   
%                Too many levels of symbolic links 
%   
%<<
%    | EOVERFLOW
%>>
%   
%                File size or position not representable 
%   
%<<
%    | EUNKNOWNERR of int
%>>
%   
%                Unknown error 
%    
%                The type of error codes.   Errors defined in the POSIX standard
%                and additional errors from UNIX98 and BSD.  All other errors
%               are mapped to EUNKNOWNERR.
%  
%<<
%  exception Unix_error of error * string * string
%>>
%    
%                Raised by the system calls below when an error is encountered. 
%               The first component is the error code; the second component  is
%               the function name; the third component is the string parameter 
%               to the function, if it has one, or the empty string otherwise.
%  
%<<
%  val error_message : error -> string
%>>
%    
%                Return a string describing the given error code.
%  
%<<
%  val handle_unix_error : ('a -> 'b) -> 'a -> 'b
%>>
%    
%                handle_unix_error f x applies f to x and returns the result. 
%               If the exception Unix_error is raised, it prints a message 
%               describing the error and exits with code 2.
%  
%
%Access to the process environment
%=================================
%  
%<<
%  val environment : unit -> string array
%>>
%    
%                Return the process environment, as an array of strings  with
%               the format --variable=value--.
%  
%<<
%  val getenv : string -> string
%>>
%    
%                Return the value associated to a variable in the process 
%               environment. Raise Not_found if the variable is unbound.  (This
%               function is identical to Sys.getenv.)
%  
%<<
%  val putenv : string -> string -> unit
%>>
%    
%                Unix.putenv name value sets the value associated to a  variable
%               in the process environment.  name is the name of the environment
%               variable,  and value its new associated value.
%  
%
%Process handling
%================
%  
%<<
%  type process_status =
%    | WEXITED of int
%>>
%   
%                The process terminated normally by exit;   the argument is the
%               return code. 
%   
%<<
%    | WSIGNALED of int
%>>
%   
%                The process was killed by a signal;  the argument is the signal
%               number. 
%   
%<<
%    | WSTOPPED of int
%>>
%   
%                The process was stopped by a signal; the argument is the 
%               signal number. 
%    
%                The termination status of a process.
%  
%<<
%  type wait_flag =
%    | WNOHANG
%>>
%   
%                do not block if no child has  died yet, but immediately return
%               with a pid equal to 0. 
%   
%<<
%    | WUNTRACED
%>>
%   
%                report also the children that receive stop signals. 
%    
%                Flags for Unix.waitpid[21.1].
%  
%<<
%  val execv : string -> string array -> 'a
%>>
%    
%                execv prog args execute the program in file prog, with  the
%               arguments args, and the current process environment.   These
%               execv* functions never return: on success, the current   program
%               is replaced by the new one;   on failure, a
%               Unix.Unix_error[21.1] exception is raised.
%  
%<<
%  val execve : string -> string array -> string array -> 'a
%>>
%    
%                Same as Unix.execv[21.1], except that the third argument
%               provides the  environment to the program executed.
%  
%<<
%  val execvp : string -> string array -> 'a
%>>
%    
%                Same as Unix.execv[21.1] respectively, except that  the program
%               is searched in the path.
%  
%<<
%  val execvpe : string -> string array -> string array -> 'a
%>>
%    
%                Same as Unix.execvp[21.1] respectively, except that  the
%               program is searched in the path.
%  
%<<
%  val fork : unit -> int
%>>
%    
%                Fork a new process. The returned integer is 0 for the child 
%               process, the pid of the child process for the parent process.
%  
%<<
%  val wait : unit -> int * process_status
%>>
%    
%                Wait until one of the children processes die, and return its
%               pid  and termination status.
%  
%<<
%  val waitpid : wait_flag list -> int -> int * process_status
%>>
%    
%                Same as Unix.wait[21.1], but waits for the child process whose
%               pid is given.  A pid of -1 means wait for any child.  A pid of 0
%               means wait for any child in the same process group  as the
%               current process.  Negative pid arguments represent process
%               groups.  The list of options indicates whether waitpid should
%               return  immediately without waiting, or also report stopped
%               children.
%  
%<<
%  val system : string -> process_status
%>>
%    
%                Execute the given command, wait until it terminates, and return
%                its termination status. The string is interpreted by the shell 
%               /bin/sh and therefore can contain redirections, quotes,
%               variables,  etc. The result WEXITED 127 indicates that the shell
%               couldn-t  be executed.
%  
%<<
%  val getpid : unit -> int
%>>
%    
%                Return the pid of the process.
%  
%<<
%  val getppid : unit -> int
%>>
%    
%                Return the pid of the parent process.
%  
%<<
%  val nice : int -> int
%>>
%    
%                Change the process priority. The integer argument is added to
%               the  --nice-- value. (Higher values of the --nice-- value mean 
%               lower priorities.) Return the new nice value.
%  
%
%Basic file input/output
%=======================
%  
%<<
%  type file_descr 
%>>
%    
%                The abstract type of file descriptors.
%  
%<<
%  val stdin : file_descr
%>>
%    
%                File descriptor for standard input.
%  
%<<
%  val stdout : file_descr
%>>
%    
%                File descriptor for standard output.
%  
%<<
%  val stderr : file_descr
%>>
%    
%                File descriptor for standard error.
%  
%<<
%  type open_flag =
%    | O_RDONLY
%>>
%   
%                Open for reading 
%   
%<<
%    | O_WRONLY
%>>
%   
%                Open for writing 
%   
%<<
%    | O_RDWR
%>>
%   
%                Open for reading and writing 
%   
%<<
%    | O_NONBLOCK
%>>
%   
%                Open in non'blocking mode 
%   
%<<
%    | O_APPEND
%>>
%   
%                Open for append 
%   
%<<
%    | O_CREAT
%>>
%   
%                Create if nonexistent 
%   
%<<
%    | O_TRUNC
%>>
%   
%                Truncate to 0 length if existing 
%   
%<<
%    | O_EXCL
%>>
%   
%                Fail if existing 
%   
%<<
%    | O_NOCTTY
%>>
%   
%                Don-t make this dev a controlling tty 
%   
%<<
%    | O_DSYNC
%>>
%   
%                Writes complete as -Synchronised I/O data integrity completion-
%               
%   
%<<
%    | O_SYNC
%>>
%   
%                Writes complete as -Synchronised I/O file integrity completion-
%               
%   
%<<
%    | O_RSYNC
%>>
%   
%                Reads complete as writes (depending on O_SYNC/O_DSYNC) 
%    
%                The flags to Unix.openfile[21.1].
%  
%<<
%  type file_perm = int 
%>>
%    
%                The type of file access rights, e.g. 0o640 is read and write
%               for user,   read for group, none for others
%  
%<<
%  val openfile : string -> open_flag list -> file_perm -> file_descr
%>>
%    
%                Open the named file with the given flags. Third argument is 
%               the permissions to give to the file if it is created. Return  a
%               file descriptor on the named file.
%  
%<<
%  val close : file_descr -> unit
%>>
%    
%                Close a file descriptor.
%  
%<<
%  val read : file_descr -> string -> int -> int -> int
%>>
%    
%                read fd buff ofs len reads len characters from descriptor  fd,
%               storing them in string buff, starting at position ofs  in string
%               buff. Return the number of characters actually read.
%  
%<<
%  val write : file_descr -> string -> int -> int -> int
%>>
%    
%                write fd buff ofs len writes len characters to descriptor  fd,
%               taking them from string buff, starting at position ofs  in
%               string buff. Return the number of characters actually  written.
%               write repeats the writing operation until all characters  have
%               been written or an error occurs.
%  
%<<
%  val single_write : file_descr -> string -> int -> int -> int
%>>
%    
%                Same as write, but attempts to write only once.  Thus, if an
%               error occurs, single_write guarantees that no data  has been
%               written.
%  
%
%Interfacing with the standard input/output library
%==================================================
%  
%<<
%  val in_channel_of_descr : file_descr -> Pervasives.in_channel
%>>
%    
%                Create an input channel reading from the given descriptor.  The
%               channel is initially in binary mode; use  set_binary_mode_in ic
%               false if text mode is desired.
%  
%<<
%  val out_channel_of_descr : file_descr -> Pervasives.out_channel
%>>
%    
%                Create an output channel writing on the given descriptor.  The
%               channel is initially in binary mode; use  set_binary_mode_out oc
%               false if text mode is desired.
%  
%<<
%  val descr_of_in_channel : Pervasives.in_channel -> file_descr
%>>
%    
%                Return the descriptor corresponding to an input channel.
%  
%<<
%  val descr_of_out_channel : Pervasives.out_channel -> file_descr
%>>
%    
%                Return the descriptor corresponding to an output channel.
%  
%
%Seeking and truncating
%======================
%  
%<<
%  type seek_command =
%    | SEEK_SET
%>>
%   
%                indicates positions relative to the beginning of the file 
%   
%<<
%    | SEEK_CUR
%>>
%   
%                indicates positions relative to the current position 
%   
%<<
%    | SEEK_END
%>>
%   
%                indicates positions relative to the end of the file 
%    
%                Positioning modes for Unix.lseek[21.1].
%  
%<<
%  val lseek : file_descr -> int -> seek_command -> int
%>>
%    
%                Set the current position for a file descriptor
%  
%<<
%  val truncate : string -> int -> unit
%>>
%    
%                Truncates the named file to the given size.
%  
%<<
%  val ftruncate : file_descr -> int -> unit
%>>
%    
%                Truncates the file corresponding to the given descriptor  to
%               the given size.
%  
%
%File statistics
%===============
%  
%<<
%  type file_kind =
%    | S_REG
%>>
%   
%                Regular file 
%   
%<<
%    | S_DIR
%>>
%   
%                Directory 
%   
%<<
%    | S_CHR
%>>
%   
%                Character device 
%   
%<<
%    | S_BLK
%>>
%   
%                Block device 
%   
%<<
%    | S_LNK
%>>
%   
%                Symbolic link 
%   
%<<
%    | S_FIFO
%>>
%   
%                Named pipe 
%   
%<<
%    | S_SOCK
%>>
%   
%                Socket 
%   
%<<
%  type stats = {
%    st_dev : int ;
%>>
%   
%                Device number 
%   
%<<
%    st_ino : int ;
%>>
%   
%                Inode number 
%   
%<<
%    st_kind : file_kind ;
%>>
%   
%                Kind of the file 
%   
%<<
%    st_perm : file_perm ;
%>>
%   
%                Access rights 
%   
%<<
%    st_nlink : int ;
%>>
%   
%                Number of links 
%   
%<<
%    st_uid : int ;
%>>
%   
%                User id of the owner 
%   
%<<
%    st_gid : int ;
%>>
%   
%                Group ID of the file-s group 
%   
%<<
%    st_rdev : int ;
%>>
%   
%                Device minor number 
%   
%<<
%    st_size : int ;
%>>
%   
%                Size in bytes 
%   
%<<
%    st_atime : float ;
%>>
%   
%                Last access time 
%   
%<<
%    st_mtime : float ;
%>>
%   
%                Last modification time 
%   
%<<
%    st_ctime : float ;
%>>
%   
%                Last status change time 
%   
%<<
%  }
%>>
%    
%                The information returned by the Unix.stat[21.1] calls.
%  
%<<
%  val stat : string -> stats
%>>
%    
%                Return the information for the named file.
%  
%<<
%  val lstat : string -> stats
%>>
%    
%                Same as Unix.stat[21.1], but in case the file is a symbolic
%               link,  return the information for the link itself.
%  
%<<
%  val fstat : file_descr -> stats
%>>
%    
%                Return the information for the file associated with the given 
%               descriptor.
%  
%
%File operations on large files
%==============================
%  
%<<
%  module LargeFile : >>
%   
%    sig
% 
%  
%   <<
%     val lseek : Unix.file_descr -> int64 -> Unix.seek_command -> int64
%   >>
%  
%   <<
%     val truncate : string -> int64 -> unit
%   >>
%  
%   <<
%     val ftruncate : Unix.file_descr -> int64 -> unit
%   >>
%  
%   <<
%     type stats = {
%       st_dev : int ;
%   >>
%  
%                   Device number 
%  
%   <<
%       st_ino : int ;
%   >>
%  
%                   Inode number 
%  
%   <<
%       st_kind : Unix.file_kind ;
%   >>
%  
%                   Kind of the file 
%  
%   <<
%       st_perm : Unix.file_perm ;
%   >>
%  
%                   Access rights 
%  
%   <<
%       st_nlink : int ;
%   >>
%  
%                   Number of links 
%  
%   <<
%       st_uid : int ;
%   >>
%  
%                   User id of the owner 
%  
%   <<
%       st_gid : int ;
%   >>
%  
%                   Group ID of the file-s group 
%  
%   <<
%       st_rdev : int ;
%   >>
%  
%                   Device minor number 
%  
%   <<
%       st_size : int64 ;
%   >>
%  
%                   Size in bytes 
%  
%   <<
%       st_atime : float ;
%   >>
%  
%                   Last access time 
%  
%   <<
%       st_mtime : float ;
%   >>
%  
%                   Last modification time 
%  
%   <<
%       st_ctime : float ;
%   >>
%  
%                   Last status change time 
%  
%   <<
%     }
%   >>
%  
%   <<
%     val stat : string -> stats
%   >>
%  
%   <<
%     val lstat : string -> stats
%   >>
%  
%   <<
%     val fstat : Unix.file_descr -> stats
%   >>
%   
%  -  end
%  
%                File operations on large files.  This sub-module provides
%               64'bit variants of the functions  Unix.lseek[21.1] (for
%               positioning a file descriptor),  Unix.truncate[21.1] and
%               Unix.ftruncate[21.1] (for changing the size of a file),  and
%               Unix.stat[21.1], Unix.lstat[21.1] and Unix.fstat[21.1] (for
%               obtaining  information on files). These alternate functions
%               represent  positions and sizes by 64'bit integers (type int64)
%               instead of  regular integers (type int), thus allowing operating
%               on files  whose sizes are greater than max_int.
%  
%
%Operations on file names
%========================
%  
%<<
%  val unlink : string -> unit
%>>
%    
%                Removes the named file
%  
%<<
%  val rename : string -> string -> unit
%>>
%    
%                rename old new changes the name of a file from old to new.
%  
%<<
%  val link : string -> string -> unit
%>>
%    
%                link source dest creates a hard link named dest to the file 
%               named source.
%  
%
%File permissions and ownership
%==============================
%  
%<<
%  type access_permission =
%    | R_OK
%>>
%   
%                Read permission 
%   
%<<
%    | W_OK
%>>
%   
%                Write permission 
%   
%<<
%    | X_OK
%>>
%   
%                Execution permission 
%   
%<<
%    | F_OK
%>>
%   
%                File exists 
%    
%                Flags for the Unix.access[21.1] call.
%  
%<<
%  val chmod : string -> file_perm -> unit
%>>
%    
%                Change the permissions of the named file.
%  
%<<
%  val fchmod : file_descr -> file_perm -> unit
%>>
%    
%                Change the permissions of an opened file.
%  
%<<
%  val chown : string -> int -> int -> unit
%>>
%    
%                Change the owner uid and owner gid of the named file.
%  
%<<
%  val fchown : file_descr -> int -> int -> unit
%>>
%    
%                Change the owner uid and owner gid of an opened file.
%  
%<<
%  val umask : int -> int
%>>
%    
%                Set the process-s file mode creation mask, and return the
%               previous  mask.
%  
%<<
%  val access : string -> access_permission list -> unit
%>>
%    
%                Check that the process has the given permissions over the named
%                file. Raise Unix_error otherwise.
%  
%
%Operations on file descriptors
%==============================
%  
%<<
%  val dup : file_descr -> file_descr
%>>
%    
%                Return a new file descriptor referencing the same file as  the
%               given descriptor.
%  
%<<
%  val dup2 : file_descr -> file_descr -> unit
%>>
%    
%                dup2 fd1 fd2 duplicates fd1 to fd2, closing fd2 if already 
%               opened.
%  
%<<
%  val set_nonblock : file_descr -> unit
%>>
%    
%                Set the --non'blocking-- flag on the given descriptor.  When
%               the non'blocking flag is set, reading on a descriptor  on which
%               there is temporarily no data available raises the  EAGAIN or
%               EWOULDBLOCK error instead of blocking;  writing on a descriptor
%               on which there is temporarily no room  for writing also raises
%               EAGAIN or EWOULDBLOCK.
%  
%<<
%  val clear_nonblock : file_descr -> unit
%>>
%    
%                Clear the --non'blocking-- flag on the given descriptor.  See
%               Unix.set_nonblock[21.1].
%  
%<<
%  val set_close_on_exec : file_descr -> unit
%>>
%    
%                Set the -'close-on-exec-- flag on the given descriptor.  A
%               descriptor with the close-on-exec flag is automatically  closed
%               when the current process starts another program with  one of the
%               exec functions.
%  
%<<
%  val clear_close_on_exec : file_descr -> unit
%>>
%    
%                Clear the -'close-on-exec-- flag on the given descriptor.  See
%               Unix.set_close_on_exec[21.1].
%  
%
%Directories
%===========
%  
%<<
%  val mkdir : string -> file_perm -> unit
%>>
%    
%                Create a directory with the given permissions.
%  
%<<
%  val rmdir : string -> unit
%>>
%    
%                Remove an empty directory.
%  
%<<
%  val chdir : string -> unit
%>>
%    
%                Change the process working directory.
%  
%<<
%  val getcwd : unit -> string
%>>
%    
%                Return the name of the current working directory.
%  
%<<
%  val chroot : string -> unit
%>>
%    
%                Change the process root directory.
%  
%<<
%  type dir_handle 
%>>
%    
%                The type of descriptors over opened directories.
%  
%<<
%  val opendir : string -> dir_handle
%>>
%    
%                Open a descriptor on a directory
%  
%<<
%  val readdir : dir_handle -> string
%>>
%    
%                Return the next entry in a directory.
%               Raises End_of_file when the end of the directory has been
%               reached.
%  
%<<
%  val rewinddir : dir_handle -> unit
%>>
%    
%                Reposition the descriptor to the beginning of the directory
%  
%<<
%  val closedir : dir_handle -> unit
%>>
%    
%                Close a directory descriptor.
%  
%
%Pipes and redirections
%======================
%  
%<<
%  val pipe : unit -> file_descr * file_descr
%>>
%    
%                Create a pipe. The first component of the result is opened  for
%               reading, that-s the exit to the pipe. The second component is 
%               opened for writing, that-s the entrance to the pipe.
%  
%<<
%  val mkfifo : string -> file_perm -> unit
%>>
%    
%                Create a named pipe with the given permissions.
%  
%
%High-level process and redirection management
%=============================================
%  
%<<
%  val create_process :
%    string ->
%    string array -> file_descr -> file_descr -> file_descr -> int
%>>
%    
%                create_process prog args new_stdin new_stdout new_stderr  forks
%               a new process that executes the program  in file prog, with
%               arguments args. The pid of the new  process is returned
%               immediately; the new process executes  concurrently with the
%               current process.  The standard input and outputs of the new
%               process are connected  to the descriptors new_stdin, new_stdout
%               and new_stderr.  Passing e.g. stdout for new_stdout prevents the
%               redirection  and causes the new process to have the same
%               standard output  as the current process.  The executable file
%               prog is searched in the path.  The new process has the same
%               environment as the current process.
%  
%<<
%  val create_process_env :
%    string ->
%    string array ->
%    string array -> file_descr -> file_descr -> file_descr -> int
%>>
%    
%                create_process_env prog args env new_stdin new_stdout
%               new_stderr  works as Unix.create_process[21.1], except that the
%               extra argument  env specifies the environment passed to the
%               program.
%  
%<<
%  val open_process_in : string -> Pervasives.in_channel
%>>
%    
%                High-level pipe and process management. This function  runs the
%               given command in parallel with the program.  The standard output
%               of the command is redirected to a pipe,  which can be read via
%               the returned input channel.  The command is interpreted by the
%               shell /bin/sh (cf. system).
%  
%<<
%  val open_process_out : string -> Pervasives.out_channel
%>>
%    
%                Same as Unix.open_process_in[21.1], but redirect the standard
%               input of  the command to a pipe. Data written to the returned
%               output channel  is sent to the standard input of the command. 
%               Warning: writes on output channels are buffered, hence be
%               careful  to call Pervasives.flush[19.2] at the right times to
%               ensure  correct synchronization.
%  
%<<
%  val open_process : string -> Pervasives.in_channel * Pervasives.out_channel
%>>
%    
%                Same as Unix.open_process_out[21.1], but redirects both the
%               standard input  and standard output of the command to pipes
%               connected to the two  returned channels. The input channel is
%               connected to the output  of the command, and the output channel
%               to the input of the command.
%  
%<<
%  val open_process_full :
%    string ->
%    string array ->
%    Pervasives.in_channel * Pervasives.out_channel * Pervasives.in_channel
%>>
%    
%                Similar to Unix.open_process[21.1], but the second argument
%               specifies  the environment passed to the command. The result is
%               a triple  of channels connected respectively to the standard
%               output, standard input,  and standard error of the command.
%  
%<<
%  val close_process_in : Pervasives.in_channel -> process_status
%>>
%    
%                Close channels opened by Unix.open_process_in[21.1],   wait for
%               the associated command to terminate,  and return its termination
%               status.
%  
%<<
%  val close_process_out : Pervasives.out_channel -> process_status
%>>
%    
%                Close channels opened by Unix.open_process_out[21.1],   wait
%               for the associated command to terminate,  and return its
%               termination status.
%  
%<<
%  val close_process :
%    Pervasives.in_channel * Pervasives.out_channel -> process_status
%>>
%    
%                Close channels opened by Unix.open_process[21.1],   wait for
%               the associated command to terminate,  and return its termination
%               status.
%  
%<<
%  val close_process_full :
%    Pervasives.in_channel * Pervasives.out_channel * Pervasives.in_channel ->
%    process_status
%>>
%    
%                Close channels opened by Unix.open_process_full[21.1],   wait
%               for the associated command to terminate,  and return its
%               termination status.
%  
%
%Symbolic links
%==============
%  
%<<
%  val symlink : string -> string -> unit
%>>
%    
%                symlink source dest creates the file dest as a symbolic link 
%               to the file source.
%  
%<<
%  val readlink : string -> string
%>>
%    
%                Read the contents of a link.
%  
%
%Polling
%=======
%  
%<<
%  val select :
%    file_descr list ->
%    file_descr list ->
%    file_descr list ->
%    float -> file_descr list * file_descr list * file_descr list
%>>
%    
%                Wait until some input/output operations become possible on 
%               some channels. The three list arguments are, respectively, a set
%                of descriptors to check for reading (first argument), for
%               writing  (second argument), or for exceptional conditions (third
%               argument).  The fourth argument is the maximal timeout, in
%               seconds; a  negative fourth argument means no timeout (unbounded
%               wait).  The result is composed of three sets of descriptors:
%               those ready  for reading (first component), ready for writing
%               (second component),  and over which an exceptional condition is
%               pending (third  component).
%  
%
%Locking
%=======
%  
%<<
%  type lock_command =
%    | F_ULOCK
%>>
%   
%                Unlock a region 
%   
%<<
%    | F_LOCK
%>>
%   
%                Lock a region for writing, and block if already locked 
%   
%<<
%    | F_TLOCK
%>>
%   
%                Lock a region for writing, or fail if already locked 
%   
%<<
%    | F_TEST
%>>
%   
%                Test a region for other process locks 
%   
%<<
%    | F_RLOCK
%>>
%   
%                Lock a region for reading, and block if already locked 
%   
%<<
%    | F_TRLOCK
%>>
%   
%                Lock a region for reading, or fail if already locked 
%    
%                Commands for Unix.lockf[21.1].
%  
%<<
%  val lockf : file_descr -> lock_command -> int -> unit
%>>
%    
%                lockf fd cmd size puts a lock on a region of the file opened 
%               as fd. The region starts at the current read/write position for 
%               fd (as set by Unix.lseek[21.1]), and extends size bytes forward
%               if  size is positive, size bytes backwards if size is negative, 
%               or to the end of the file if size is zero.  A write lock
%               prevents any other  process from acquiring a read or write lock
%               on the region.  A read lock prevents any other  process from
%               acquiring a write lock on the region, but lets  other processes
%               acquire read locks on it.
%               The F_LOCK and F_TLOCK commands attempts to put a write lock  on
%               the specified region.  The F_RLOCK and F_TRLOCK commands
%               attempts to put a read lock  on the specified region.  If one or
%               several locks put by another process prevent the current process
%                from acquiring the lock, F_LOCK and F_RLOCK block until these
%               locks  are removed, while F_TLOCK and F_TRLOCK fail immediately
%               with an  exception.  The F_ULOCK removes whatever locks the
%               current process has on  the specified region.  Finally, the
%               F_TEST command tests whether a write lock can be  acquired on
%               the specified region, without actually putting a lock.  It
%               returns immediately if successful, or fails otherwise.
%  
%
%Signals
%=======
%  
%  Note: installation of signal handlers is performed via  the functions
%Sys.signal[20.34] and Sys.set_signal[20.34].
%<<
%  val kill : int -> int -> unit
%>>
%    
%                kill pid sig sends signal number sig to the process  with id
%               pid.
%  
%<<
%  type sigprocmask_command =
%    | SIG_SETMASK
%    | SIG_BLOCK
%    | SIG_UNBLOCK
%>>
%   
%<<
%  val sigprocmask : sigprocmask_command -> int list -> int list
%>>
%    
%                sigprocmask cmd sigs changes the set of blocked signals.  If
%               cmd is SIG_SETMASK, blocked signals are set to those in  the
%               list sigs.  If cmd is SIG_BLOCK, the signals in sigs are added
%               to  the set of blocked signals.  If cmd is SIG_UNBLOCK, the
%               signals in sigs are removed  from the set of blocked signals. 
%               sigprocmask returns the set of previously blocked signals.
%  
%<<
%  val sigpending : unit -> int list
%>>
%    
%                Return the set of blocked signals that are currently pending.
%  
%<<
%  val sigsuspend : int list -> unit
%>>
%    
%                sigsuspend sigs atomically sets the blocked signals to sigs 
%               and waits for a non-ignored, non'blocked signal to be delivered.
%                On return, the blocked signals are reset to their initial
%               value.
%  
%<<
%  val pause : unit -> unit
%>>
%    
%                Wait until a non-ignored, non'blocked signal is delivered.
%  
%
%Time functions
%==============
%  
%<<
%  type process_times = {
%    tms_utime : float ;
%>>
%   
%                User time for the process 
%   
%<<
%    tms_stime : float ;
%>>
%   
%                System time for the process 
%   
%<<
%    tms_cutime : float ;
%>>
%   
%                User time for the children processes 
%   
%<<
%    tms_cstime : float ;
%>>
%   
%                System time for the children processes 
%   
%<<
%  }
%>>
%    
%                The execution times (CPU times) of a process.
%  
%<<
%  type tm = {
%    tm_sec : int ;
%>>
%   
%                Seconds 0..60 
%   
%<<
%    tm_min : int ;
%>>
%   
%                Minutes 0..59 
%   
%<<
%    tm_hour : int ;
%>>
%   
%                Hours 0..23 
%   
%<<
%    tm_mday : int ;
%>>
%   
%                Day of month 1..31 
%   
%<<
%    tm_mon : int ;
%>>
%   
%                Month of year 0..11 
%   
%<<
%    tm_year : int ;
%>>
%   
%                Year - 1900 
%   
%<<
%    tm_wday : int ;
%>>
%   
%                Day of week (Sunday is 0) 
%   
%<<
%    tm_yday : int ;
%>>
%   
%                Day of year 0..365 
%   
%<<
%    tm_isdst : bool ;
%>>
%   
%                Daylight time savings in effect 
%   
%<<
%  }
%>>
%    
%                The type representing wallclock time and calendar date.
%  
%<<
%  val time : unit -> float
%>>
%    
%                Return the current time since 00:00:00 GMT, Jan. 1, 1970,  in
%               seconds.
%  
%<<
%  val gettimeofday : unit -> float
%>>
%    
%                Same as Unix.time[21.1], but with resolution better than 1
%               second.
%  
%<<
%  val gmtime : float -> tm
%>>
%    
%                Convert a time in seconds, as returned by Unix.time[21.1], into
%               a date and  a time. Assumes UTC (Coordinated Universal Time),
%               also known as GMT.
%  
%<<
%  val localtime : float -> tm
%>>
%    
%                Convert a time in seconds, as returned by Unix.time[21.1], into
%               a date and  a time. Assumes the local time zone.
%  
%<<
%  val mktime : tm -> float * tm
%>>
%    
%                Convert a date and time, specified by the tm argument, into  a
%               time in seconds, as returned by Unix.time[21.1]. The tm_isdst, 
%               tm_wday and tm_yday fields of tm are ignored. Also return a 
%               normalized copy of the given tm record, with the tm_wday, 
%               tm_yday, and tm_isdst fields recomputed from the other fields, 
%               and the other fields normalized (so that, e.g., 40 October is 
%               changed into 9 November). The tm argument is interpreted in the 
%               local time zone.
%  
%<<
%  val alarm : int -> int
%>>
%    
%                Schedule a SIGALRM signal after the given number of seconds.
%  
%<<
%  val sleep : int -> unit
%>>
%    
%                Stop execution for the given number of seconds.
%  
%<<
%  val times : unit -> process_times
%>>
%    
%                Return the execution times of the process.
%  
%<<
%  val utimes : string -> float -> float -> unit
%>>
%    
%                Set the last access time (second arg) and last modification
%               time  (third arg) for a file. Times are expressed in seconds
%               from  00:00:00 GMT, Jan. 1, 1970.
%  
%<<
%  type interval_timer =
%    | ITIMER_REAL
%>>
%   
%                decrements in real time, and sends the signal SIGALRM when
%               expired. 
%   
%<<
%    | ITIMER_VIRTUAL
%>>
%   
%                decrements in process virtual time, and sends SIGVTALRM when
%               expired. 
%   
%<<
%    | ITIMER_PROF
%>>
%   
%                (for profiling) decrements both when the process  is running
%               and when the system is running on behalf of the  process; it
%               sends SIGPROF when expired. 
%    
%                The three kinds of interval timers.
%  
%<<
%  type interval_timer_status = {
%    it_interval : float ;
%>>
%   
%                Period 
%   
%<<
%    it_value : float ;
%>>
%   
%                Current value of the timer 
%   
%<<
%  }
%>>
%    
%                The type describing the status of an interval timer
%  
%<<
%  val getitimer : interval_timer -> interval_timer_status
%>>
%    
%                Return the current status of the given interval timer.
%  
%<<
%  val setitimer :
%    interval_timer ->
%    interval_timer_status -> interval_timer_status
%>>
%    
%                setitimer t s sets the interval timer t and returns  its
%               previous status. The s argument is interpreted as follows: 
%               s.it_value, if nonzero, is the time to the next timer
%               expiration;  s.it_interval, if nonzero, specifies a value to  be
%               used in reloading it_value when the timer expires.  Setting
%               s.it_value to zero disable the timer.  Setting s.it_interval to
%               zero causes the timer to be disabled  after its next expiration.
%  
%
%User id, group id
%=================
%  
%<<
%  val getuid : unit -> int
%>>
%    
%                Return the user id of the user executing the process.
%  
%<<
%  val geteuid : unit -> int
%>>
%    
%                Return the effective user id under which the process runs.
%  
%<<
%  val setuid : int -> unit
%>>
%    
%                Set the real user id and effective user id for the process.
%  
%<<
%  val getgid : unit -> int
%>>
%    
%                Return the group id of the user executing the process.
%  
%<<
%  val getegid : unit -> int
%>>
%    
%                Return the effective group id under which the process runs.
%  
%<<
%  val setgid : int -> unit
%>>
%    
%                Set the real group id and effective group id for the process.
%  
%<<
%  val getgroups : unit -> int array
%>>
%    
%                Return the list of groups to which the user executing the
%               process  belongs.
%  
%<<
%  type passwd_entry = {
%    pw_name : string ;
%    pw_passwd : string ;
%    pw_uid : int ;
%    pw_gid : int ;
%    pw_gecos : string ;
%    pw_dir : string ;
%    pw_shell : string ;
%  }
%>>
%    
%                Structure of entries in the passwd database.
%  
%<<
%  type group_entry = {
%    gr_name : string ;
%    gr_passwd : string ;
%    gr_gid : int ;
%    gr_mem : string array ;
%  }
%>>
%    
%                Structure of entries in the groups database.
%  
%<<
%  val getlogin : unit -> string
%>>
%    
%                Return the login name of the user executing the process.
%  
%<<
%  val getpwnam : string -> passwd_entry
%>>
%    
%                Find an entry in passwd with the given name, or raise 
%               Not_found.
%  
%<<
%  val getgrnam : string -> group_entry
%>>
%    
%                Find an entry in group with the given name, or raise 
%               Not_found.
%  
%<<
%  val getpwuid : int -> passwd_entry
%>>
%    
%                Find an entry in passwd with the given user id, or raise 
%               Not_found.
%  
%<<
%  val getgrgid : int -> group_entry
%>>
%    
%                Find an entry in group with the given group id, or raise 
%               Not_found.
%  
%
%Internet addresses
%==================
%  
%<<
%  type inet_addr 
%>>
%    
%                The abstract type of Internet addresses.
%  
%<<
%  val inet_addr_of_string : string -> inet_addr
%>>
%    
%                Conversion from the printable representation of an Internet 
%               address to its internal representation. The argument string 
%               consists of 4 numbers separated by periods (XXX.YYY.ZZZ.TTT) 
%               for IPv4 addresses, and up to 8 numbers separated by colons  for
%               IPv6 addresses. Raise Failure when given a string that  does not
%               match these formats.
%  
%<<
%  val string_of_inet_addr : inet_addr -> string
%>>
%    
%                Return the printable representation of the given Internet
%               address.  See Unix.inet_addr_of_string[21.1] for a description
%               of the  printable representation.
%  
%<<
%  val inet_addr_any : inet_addr
%>>
%    
%                A special IPv4 address, for use only with bind, representing 
%               all the Internet addresses that the host machine possesses.
%  
%<<
%  val inet_addr_loopback : inet_addr
%>>
%    
%                A special IPv4 address representing the host machine
%               (127.0.0.1).
%  
%<<
%  val inet6_addr_any : inet_addr
%>>
%    
%                A special IPv6 address, for use only with bind, representing 
%               all the Internet addresses that the host machine possesses.
%  
%<<
%  val inet6_addr_loopback : inet_addr
%>>
%    
%                A special IPv6 address representing the host machine (::1).
%  
%
%Sockets
%=======
%  
%<<
%  type socket_domain =
%    | PF_UNIX
%>>
%   
%                Unix domain 
%   
%<<
%    | PF_INET
%>>
%   
%                Internet domain (IPv4) 
%   
%<<
%    | PF_INET6
%>>
%   
%                Internet domain (IPv6) 
%    
%                The type of socket domains.
%  
%<<
%  type socket_type =
%    | SOCK_STREAM
%>>
%   
%                Stream socket 
%   
%<<
%    | SOCK_DGRAM
%>>
%   
%                Datagram socket 
%   
%<<
%    | SOCK_RAW
%>>
%   
%                Raw socket 
%   
%<<
%    | SOCK_SEQPACKET
%>>
%   
%                Sequenced packets socket 
%    
%                The type of socket kinds, specifying the semantics of 
%               communications.
%  
%<<
%  type sockaddr =
%    | ADDR_UNIX of string
%    | ADDR_INET of inet_addr * int
%>>
%   
%                The type of socket addresses. ADDR_UNIX name is a socket 
%               address in the Unix domain; name is a file name in the file 
%               system. ADDR_INET(addr,port) is a socket address in the Internet
%                domain; addr is the Internet address of the machine, and  port
%               is the port number. 
%   
%<<
%  val socket : socket_domain -> socket_type -> int -> file_descr
%>>
%    
%                Create a new socket in the given domain, and with the  given
%               kind. The third argument is the protocol type; 0 selects  the
%               default protocol for that kind of sockets.
%  
%<<
%  val domain_of_sockaddr : sockaddr -> socket_domain
%>>
%    
%                Return the socket domain adequate for the given socket address.
%  
%<<
%  val socketpair :
%    socket_domain ->
%    socket_type -> int -> file_descr * file_descr
%>>
%    
%                Create a pair of unnamed sockets, connected together.
%  
%<<
%  val accept : file_descr -> file_descr * sockaddr
%>>
%    
%                Accept connections on the given socket. The returned descriptor
%                is a socket connected to the client; the returned address is 
%               the address of the connecting client.
%  
%<<
%  val bind : file_descr -> sockaddr -> unit
%>>
%    
%                Bind a socket to an address.
%  
%<<
%  val connect : file_descr -> sockaddr -> unit
%>>
%    
%                Connect a socket to an address.
%  
%<<
%  val listen : file_descr -> int -> unit
%>>
%    
%                Set up a socket for receiving connection requests. The integer 
%               argument is the maximal number of pending requests.
%  
%<<
%  type shutdown_command =
%    | SHUTDOWN_RECEIVE
%>>
%   
%                Close for receiving 
%   
%<<
%    | SHUTDOWN_SEND
%>>
%   
%                Close for sending 
%   
%<<
%    | SHUTDOWN_ALL
%>>
%   
%                Close both 
%    
%                The type of commands for shutdown.
%  
%<<
%  val shutdown : file_descr -> shutdown_command -> unit
%>>
%    
%                Shutdown a socket connection. SHUTDOWN_SEND as second argument 
%               causes reads on the other end of the connection to return  an
%               end-of-file condition.  SHUTDOWN_RECEIVE causes writes on the
%               other end of the connection  to return a closed pipe condition
%               (SIGPIPE signal).
%  
%<<
%  val getsockname : file_descr -> sockaddr
%>>
%    
%                Return the address of the given socket.
%  
%<<
%  val getpeername : file_descr -> sockaddr
%>>
%    
%                Return the address of the host connected to the given socket.
%  
%<<
%  type msg_flag =
%    | MSG_OOB
%    | MSG_DONTROUTE
%    | MSG_PEEK
%>>
%   
%                The flags for Unix.recv[21.1], Unix.recvfrom[21.1],  
%               Unix.send[21.1] and Unix.sendto[21.1]. 
%   
%<<
%  val recv : file_descr -> string -> int -> int -> msg_flag list -> int
%>>
%    
%                Receive data from a connected socket.
%  
%<<
%  val recvfrom :
%    file_descr ->
%    string -> int -> int -> msg_flag list -> int * sockaddr
%>>
%    
%                Receive data from an unconnected socket.
%  
%<<
%  val send : file_descr -> string -> int -> int -> msg_flag list -> int
%>>
%    
%                Send data over a connected socket.
%  
%<<
%  val sendto :
%    file_descr ->
%    string -> int -> int -> msg_flag list -> sockaddr -> int
%>>
%    
%                Send data over an unconnected socket.
%  
%
%Socket options
%==============
%  
%<<
%  type socket_bool_option =
%    | SO_DEBUG
%>>
%   
%                Record debugging information 
%   
%<<
%    | SO_BROADCAST
%>>
%   
%                Permit sending of broadcast messages 
%   
%<<
%    | SO_REUSEADDR
%>>
%   
%                Allow reuse of local addresses for bind 
%   
%<<
%    | SO_KEEPALIVE
%>>
%   
%                Keep connection active 
%   
%<<
%    | SO_DONTROUTE
%>>
%   
%                Bypass the standard routing algorithms 
%   
%<<
%    | SO_OOBINLINE
%>>
%   
%                Leave out-of'band data in line 
%   
%<<
%    | SO_ACCEPTCONN
%>>
%   
%                Report whether socket listening is enabled 
%    
%                The socket options that can be consulted with
%               Unix.getsockopt[21.1]  and modified with Unix.setsockopt[21.1].
%               These options have a boolean  (true/false) value.
%  
%<<
%  type socket_int_option =
%    | SO_SNDBUF
%>>
%   
%                Size of send buffer 
%   
%<<
%    | SO_RCVBUF
%>>
%   
%                Size of received buffer 
%   
%<<
%    | SO_ERROR
%>>
%   
%                Report the error status and clear it 
%   
%<<
%    | SO_TYPE
%>>
%   
%                Report the socket type 
%   
%<<
%    | SO_RCVLOWAT
%>>
%   
%                Minimum number of bytes to process for input operations 
%   
%<<
%    | SO_SNDLOWAT
%>>
%   
%                Minimum number of bytes to process for output operations 
%    
%                The socket options that can be consulted with
%               Unix.getsockopt_int[21.1]  and modified with
%               Unix.setsockopt_int[21.1]. These options have an  integer value.
%  
%<<
%  type socket_optint_option =
%    | SO_LINGER
%>>
%   
%                Whether to linger on closed connections  that have data
%               present, and for how long  (in seconds) 
%    
%                The socket options that can be consulted with
%               Unix.getsockopt_optint[21.1]  and modified with
%               Unix.setsockopt_optint[21.1]. These options have a  value of
%               type int option, with None meaning --disabled--.
%  
%<<
%  type socket_float_option =
%    | SO_RCVTIMEO
%>>
%   
%                Timeout for input operations 
%   
%<<
%    | SO_SNDTIMEO
%>>
%   
%                Timeout for output operations 
%    
%                The socket options that can be consulted with
%               Unix.getsockopt_float[21.1]  and modified with
%               Unix.setsockopt_float[21.1]. These options have a 
%               floating-point value representing a time in seconds.  The value
%               0 means infinite timeout.
%  
%<<
%  val getsockopt : file_descr -> socket_bool_option -> bool
%>>
%    
%                Return the current status of a boolean-valued option  in the
%               given socket.
%  
%<<
%  val setsockopt : file_descr -> socket_bool_option -> bool -> unit
%>>
%    
%                Set or clear a boolean-valued option in the given socket.
%  
%<<
%  val getsockopt_int : file_descr -> socket_int_option -> int
%>>
%    
%                Same as Unix.getsockopt[21.1] for an integer-valued socket
%               option.
%  
%<<
%  val setsockopt_int : file_descr -> socket_int_option -> int -> unit
%>>
%    
%                Same as Unix.setsockopt[21.1] for an integer-valued socket
%               option.
%  
%<<
%  val getsockopt_optint : file_descr -> socket_optint_option -> int option
%>>
%    
%                Same as Unix.getsockopt[21.1] for a socket option whose value
%               is an int option.
%  
%<<
%  val setsockopt_optint :
%    file_descr -> socket_optint_option -> int option -> unit
%>>
%    
%                Same as Unix.setsockopt[21.1] for a socket option whose value
%               is an int option.
%  
%<<
%  val getsockopt_float : file_descr -> socket_float_option -> float
%>>
%    
%                Same as Unix.getsockopt[21.1] for a socket option whose value
%               is a floating-point number.
%  
%<<
%  val setsockopt_float : file_descr -> socket_float_option -> float -> unit
%>>
%    
%                Same as Unix.setsockopt[21.1] for a socket option whose value
%               is a floating-point number.
%  
%
%High-level network connection functions
%=======================================
%  
%<<
%  val open_connection :
%    sockaddr -> Pervasives.in_channel * Pervasives.out_channel
%>>
%    
%                Connect to a server at the given address.  Return a pair of
%               buffered channels connected to the server.  Remember to call
%               Pervasives.flush[19.2] on the output channel at the right  times
%               to ensure correct synchronization.
%  
%<<
%  val shutdown_connection : Pervasives.in_channel -> unit
%>>
%    
%                --Shut down-- a connection established with
%               Unix.open_connection[21.1];  that is, transmit an end-of-file
%               condition to the server reading  on the other side of the
%               connection.
%  
%<<
%  val establish_server :
%    (Pervasives.in_channel -> Pervasives.out_channel -> unit) ->
%    sockaddr -> unit
%>>
%    
%                Establish a server on the given address.  The function given as
%               first argument is called for each connection  with two buffered
%               channels connected to the client. A new process  is created for
%               each connection. The function Unix.establish_server[21.1]  never
%               returns normally.
%  
%
%Host and protocol databases
%===========================
%  
%<<
%  type host_entry = {
%    h_name : string ;
%    h_aliases : string array ;
%    h_addrtype : socket_domain ;
%    h_addr_list : inet_addr array ;
%  }
%>>
%    
%                Structure of entries in the hosts database.
%  
%<<
%  type protocol_entry = {
%    p_name : string ;
%    p_aliases : string array ;
%    p_proto : int ;
%  }
%>>
%    
%                Structure of entries in the protocols database.
%  
%<<
%  type service_entry = {
%    s_name : string ;
%    s_aliases : string array ;
%    s_port : int ;
%    s_proto : string ;
%  }
%>>
%    
%                Structure of entries in the services database.
%  
%<<
%  val gethostname : unit -> string
%>>
%    
%                Return the name of the local host.
%  
%<<
%  val gethostbyname : string -> host_entry
%>>
%    
%                Find an entry in hosts with the given name, or raise 
%               Not_found.
%  
%<<
%  val gethostbyaddr : inet_addr -> host_entry
%>>
%    
%                Find an entry in hosts with the given address, or raise 
%               Not_found.
%  
%<<
%  val getprotobyname : string -> protocol_entry
%>>
%    
%                Find an entry in protocols with the given name, or raise 
%               Not_found.
%  
%<<
%  val getprotobynumber : int -> protocol_entry
%>>
%    
%                Find an entry in protocols with the given protocol number,  or
%               raise Not_found.
%  
%<<
%  val getservbyname : string -> string -> service_entry
%>>
%    
%                Find an entry in services with the given name, or raise 
%               Not_found.
%  
%<<
%  val getservbyport : int -> string -> service_entry
%>>
%    
%                Find an entry in services with the given service number,  or
%               raise Not_found.
%  
%<<
%  type addr_info = {
%    ai_family : socket_domain ;
%>>
%   
%                Socket domain 
%   
%<<
%    ai_socktype : socket_type ;
%>>
%   
%                Socket type 
%   
%<<
%    ai_protocol : int ;
%>>
%   
%                Socket protocol number 
%   
%<<
%    ai_addr : sockaddr ;
%>>
%   
%                Address 
%   
%<<
%    ai_canonname : string ;
%>>
%   
%                Canonical host name 
%   
%<<
%  }
%>>
%    
%                Address information returned by Unix.getaddrinfo[21.1].
%  
%<<
%  type getaddrinfo_option =
%    | AI_FAMILY of socket_domain
%>>
%   
%                Impose the given socket domain 
%   
%<<
%    | AI_SOCKTYPE of socket_type
%>>
%   
%                Impose the given socket type 
%   
%<<
%    | AI_PROTOCOL of int
%>>
%   
%                Impose the given protocol 
%   
%<<
%    | AI_NUMERICHOST
%>>
%   
%                Do not call name resolver,   expect numeric IP address 
%   
%<<
%    | AI_CANONNAME
%>>
%   
%                Fill the ai_canonname field  of the result 
%   
%<<
%    | AI_PASSIVE
%>>
%   
%                Set address to -'any-- address  for use with Unix.bind[21.1] 
%    
%                Options to Unix.getaddrinfo[21.1].
%  
%<<
%  val getaddrinfo :
%    string -> string -> getaddrinfo_option list -> addr_info list
%>>
%    
%                getaddrinfo host service opts returns a list of
%               Unix.addr_info[21.1]  records describing socket parameters and
%               addresses suitable for  communicating with the given host and
%               service. The empty list is  returned if the host or service
%               names are unknown, or the constraints  expressed in opts cannot
%               be satisfied.
%               host is either a host name or the string representation of an IP
%                address. host can be given as the empty string; in this case, 
%               the -'any-- address or the --loopback-- address are used, 
%               depending whether opts contains AI_PASSIVE.  service is either a
%               service name or the string representation of  a port number.
%               service can be given as the empty string;  in this case, the
%               port field of the returned addresses is set to 0.  opts is a
%               possibly empty list of options that allows the caller  to force
%               a particular socket domain (e.g. IPv6 only or IPv4 only)  or a
%               particular socket type (e.g. TCP only or UDP only).
%  
%<<
%  type name_info = {
%    ni_hostname : string ;
%>>
%   
%                Name or IP address of host 
%   
%<<
%    ni_service : string ;
%  }
%>>
%    
%                Name of service or port number
%  
%  Host and service information returned by Unix.getnameinfo[21.1].
%<<
%  type getnameinfo_option =
%    | NI_NOFQDN
%>>
%   
%                Do not qualify local host names 
%   
%<<
%    | NI_NUMERICHOST
%>>
%   
%                Always return host as IP address 
%   
%<<
%    | NI_NAMEREQD
%>>
%   
%                Fail if host name cannot be determined 
%   
%<<
%    | NI_NUMERICSERV
%>>
%   
%                Always return service as port number 
%   
%<<
%    | NI_DGRAM
%>>
%   
%                Consider the service as UDP'based  instead of the default TCP 
%    
%                Options to Unix.getnameinfo[21.1].
%  
%<<
%  val getnameinfo : sockaddr -> getnameinfo_option list -> name_info
%>>
%    
%                getnameinfo addr opts returns the host name and service name 
%               corresponding to the socket address addr. opts is a possibly 
%               empty list of options that governs how these names are obtained.
%                Raise Not_found if an error occurs.
%  
%
%Terminal interface
%==================
%  
%  The following functions implement the POSIX standard terminal  interface.
%They provide control over asynchronous communication ports  and
%pseudo-terminals. Refer to the termios man page for a  complete description.
%<<
%  type terminal_io = {
%    mutable c_ignbrk : bool ;
%>>
%   
%                Ignore the break condition. 
%   
%<<
%    mutable c_brkint : bool ;
%>>
%   
%                Signal interrupt on break condition. 
%   
%<<
%    mutable c_ignpar : bool ;
%>>
%   
%                Ignore characters with parity errors. 
%   
%<<
%    mutable c_parmrk : bool ;
%>>
%   
%                Mark parity errors. 
%   
%<<
%    mutable c_inpck : bool ;
%>>
%   
%                Enable parity check on input. 
%   
%<<
%    mutable c_istrip : bool ;
%>>
%   
%                Strip 8th bit on input characters. 
%   
%<<
%    mutable c_inlcr : bool ;
%>>
%   
%                Map NL to CR on input. 
%   
%<<
%    mutable c_igncr : bool ;
%>>
%   
%                Ignore CR on input. 
%   
%<<
%    mutable c_icrnl : bool ;
%>>
%   
%                Map CR to NL on input. 
%   
%<<
%    mutable c_ixon : bool ;
%>>
%   
%                Recognize XON/XOFF characters on input. 
%   
%<<
%    mutable c_ixoff : bool ;
%>>
%   
%                Emit XON/XOFF chars to control input flow. 
%   
%<<
%    mutable c_opost : bool ;
%>>
%   
%                Enable output processing. 
%   
%<<
%    mutable c_obaud : int ;
%>>
%   
%                Output baud rate (0 means close connection). 
%   
%<<
%    mutable c_ibaud : int ;
%>>
%   
%                Input baud rate. 
%   
%<<
%    mutable c_csize : int ;
%>>
%   
%                Number of bits per character (5-8). 
%   
%<<
%    mutable c_cstopb : int ;
%>>
%   
%                Number of stop bits (1-2). 
%   
%<<
%    mutable c_cread : bool ;
%>>
%   
%                Reception is enabled. 
%   
%<<
%    mutable c_parenb : bool ;
%>>
%   
%                Enable parity generation and detection. 
%   
%<<
%    mutable c_parodd : bool ;
%>>
%   
%                Specify odd parity instead of even. 
%   
%<<
%    mutable c_hupcl : bool ;
%>>
%   
%                Hang up on last close. 
%   
%<<
%    mutable c_clocal : bool ;
%>>
%   
%                Ignore modem status lines. 
%   
%<<
%    mutable c_isig : bool ;
%>>
%   
%                Generate signal on INTR, QUIT, SUSP. 
%   
%<<
%    mutable c_icanon : bool ;
%>>
%   
%                Enable canonical processing  (line buffering and editing) 
%   
%<<
%    mutable c_noflsh : bool ;
%>>
%   
%                Disable flush after INTR, QUIT, SUSP. 
%   
%<<
%    mutable c_echo : bool ;
%>>
%   
%                Echo input characters. 
%   
%<<
%    mutable c_echoe : bool ;
%>>
%   
%                Echo ERASE (to erase previous character). 
%   
%<<
%    mutable c_echok : bool ;
%>>
%   
%                Echo KILL (to erase the current line). 
%   
%<<
%    mutable c_echonl : bool ;
%>>
%   
%                Echo NL even if c_echo is not set. 
%   
%<<
%    mutable c_vintr : char ;
%>>
%   
%                Interrupt character (usually ctrl'c). 
%   
%<<
%    mutable c_vquit : char ;
%>>
%   
%                Quit character (usually ctrl-\). 
%   
%<<
%    mutable c_verase : char ;
%>>
%   
%                Erase character (usually DEL or ctrl-H). 
%   
%<<
%    mutable c_vkill : char ;
%>>
%   
%                Kill line character (usually ctrl-U). 
%   
%<<
%    mutable c_veof : char ;
%>>
%   
%                End-of-file character (usually ctrl-D). 
%   
%<<
%    mutable c_veol : char ;
%>>
%   
%                Alternate end-of-line char. (usually none). 
%   
%<<
%    mutable c_vmin : int ;
%>>
%   
%                Minimum number of characters to read  before the read request
%               is satisfied. 
%   
%<<
%    mutable c_vtime : int ;
%>>
%   
%                Maximum read wait (in 0.1s units). 
%   
%<<
%    mutable c_vstart : char ;
%>>
%   
%                Start character (usually ctrl-Q). 
%   
%<<
%    mutable c_vstop : char ;
%>>
%   
%                Stop character (usually ctrl-S). 
%   
%<<
%  }
%>>
%   
%<<
%  val tcgetattr : file_descr -> terminal_io
%>>
%    
%                Return the status of the terminal referred to by the given 
%               file descriptor.
%  
%<<
%  type setattr_when =
%    | TCSANOW
%    | TCSADRAIN
%    | TCSAFLUSH
%>>
%   
%<<
%  val tcsetattr : file_descr -> setattr_when -> terminal_io -> unit
%>>
%    
%                Set the status of the terminal referred to by the given  file
%               descriptor. The second argument indicates when the  status
%               change takes place: immediately (TCSANOW),  when all pending
%               output has been transmitted (TCSADRAIN),  or after flushing all
%               input that has been received but not  read (TCSAFLUSH).
%               TCSADRAIN is recommended when changing  the output parameters;
%               TCSAFLUSH, when changing the input  parameters.
%  
%<<
%  val tcsendbreak : file_descr -> int -> unit
%>>
%    
%                Send a break condition on the given file descriptor.  The
%               second argument is the duration of the break, in 0.1s units;  0
%               means standard duration (0.25s).
%  
%<<
%  val tcdrain : file_descr -> unit
%>>
%    
%                Waits until all output written on the given file descriptor 
%               has been transmitted.
%  
%<<
%  type flush_queue =
%    | TCIFLUSH
%    | TCOFLUSH
%    | TCIOFLUSH
%>>
%   
%<<
%  val tcflush : file_descr -> flush_queue -> unit
%>>
%    
%                Discard data written on the given file descriptor but not yet 
%               transmitted, or data received but not yet read, depending on the
%                second argument: TCIFLUSH flushes data received but not read, 
%               TCOFLUSH flushes data written but not transmitted, and 
%               TCIOFLUSH flushes both.
%  
%<<
%  type flow_action =
%    | TCOOFF
%    | TCOON
%    | TCIOFF
%    | TCION
%>>
%   
%<<
%  val tcflow : file_descr -> flow_action -> unit
%>>
%    
%                Suspend or restart reception or transmission of data on  the
%               given file descriptor, depending on the second argument:  TCOOFF
%               suspends output, TCOON restarts output,  TCIOFF transmits a STOP
%               character to suspend input,  and TCION transmits a START
%               character to restart input.
%  
%<<
%  val setsid : unit -> int
%>>
%    
%                Put the calling process in a new session and detach it from 
%               its controlling terminal.
%  
%  
%
%21.2  Module UnixLabels: labelized version of the interface
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%    
%  This module is identical to Unix (21.1), and only differs by the addition of
%labels. You may see these labels directly by looking at unixLabels.mli, or by
%using the ocamlbrowser tool. 
%     Windows: 
%                The Cygwin port of Objective Caml fully implements all
%               functions from the Unix module. The native Win32 ports implement
%               a subset of them. Below is a list of the functions that are not
%               implemented, or only partially implemented, by the Win32 ports.
%               Functions not mentioned are fully implemented and behave as
%               described previously in this chapter.
%                                                
%                    ------------------------------------------------------
%                    |         Functions          |        Comment        |
%                    ------------------------------------------------------
%                    |fork                        |not implemented, use   |
%                    |                            |create_process or      |
%                    |                            |threads                |
%                    |wait                        |not implemented, use   |
%                    |                            |waitpid                |
%                    |waitpid                     |can only wait for a    |
%                    |                            |given PID, not any     |
%                    |                            |child process          |
%                    |getppid                     |not implemented        |
%                    |                            |(meaningless under     |
%                    |                            |Windows)               |
%                    |nice                        |not implemented        |
%                    |in_channel_of_descr         |does not work on       |
%                    |                            |sockets under Windows  |
%                    |                            |95, 98, ME; works fine |
%                    |                            |under NT, 2000, XP     |
%                    |out_channel_of_descr        |ditto                  |
%                    |truncate, ftruncate         |not implemented        |
%                    |lstat, fstat                |not implemented        |
%                    |link, symlink, readlink     |not implemented (no    |
%                    |                            |links under Windows)   |
%                    |fchmod                      |not implemented        |
%                    |chown, fchown               |not implemented (make  |
%                    |                            |no sense on a DOS file |
%                    |                            |system)                |
%                    |umask                       |not implemented        |
%                    |set_nonblock, clear_nonblock|implemented as dummy   |
%                    |                            |functions; use threads |
%                    |                            |instead of non'blocking|
%                    |                            |I/O                    |
%                    |rewinddir                   |not implemented;       |
%                    |                            |re-open the directory  |
%                    |                            |instead                |
%                    |mkfifo                      |not implemented        |
%                    |select                      |implemented, but works |
%                    |                            |only for sockets; use  |
%                    |                            |threads  if you need to|
%                    |                            |wait on other kinds of |
%                    |                            |file descriptors       |
%                    |lockf                       |not implemented        |
%                    |kill, pause                 |not implemented (no    |
%                    |                            |inter-process signals  |
%                    |                            |in Windows)            |
%                    |alarm, times                |not implemented        |
%                    |getitimer, setitimer        |not implemented        |
%                    |getuid, getgid              |always return 1        |
%                    |getgid, getegid, getgroups  |not implemented        |
%                    |setuid, setgid              |not implemented        |
%                    |getpwnam, getpwuid          |always raise Not_found |
%                    |getgrnam, getgrgid          |always raise Not_found |
%                    |type socket_domain          |the domain PF_UNIX is  |
%                    |                            |not supported; PF_INET |
%                    |                            |is fully supported     |
%                    |open_connection             |does not work under    |
%                    |                            |Windows 95, 98, ME;    |
%                    |                            |works fine under NT,   |
%                    |                            |2000, XP               |
%                    |establish_server            |not implemented; use   |
%                    |                            |threads                |
%                    |terminal functions (tc*)    |not implemented        |
%                    ------------------------------------------------------
%  
%    
%  
%
%Chapter 22    The num library: arbitrary-precision rational arithmetic
%**********************************************************************
%   
%  The num library implements integer arithmetic and rational arithmetic in
%arbitrary precision.
%  More documentation on the functions provided in this library can be found in
%The CAML Numbers Reference Manual by  Valrie Mnissier-Morain, technical
%report 141, INRIA, july 1992 (available electronically,
%ftp://ftp.inria.fr/INRIA/publication/RT/RT-0141.ps.gz).
%  Programs that use the num library must be linked as follows: 
%<<
%          ocamlc other options nums.cma other files
%          ocamlopt other options nums.cmxa other files
%>>
%   For interactive use of the nums library, do: 
%<<
%          ocamlmktop -o mytop nums.cma
%          ./mytop
%>>
%   or (if dynamic linking of C libraries is supported on your platform), start
%ocaml and type #load "nums.cma";;.
%  
%
%22.1  Module Num : Operation on arbitrary-precision numbers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  Numbers (type num) are arbitrary-precision rational numbers,  plus the
%special elements 1/0 (infinity) and 0/0 (undefined).
%  0.5cm
%<<
%  type num =
%    | Int of int
%    | Big_int of Big_int.big_int
%    | Ratio of Ratio.ratio
%>>
%    
%                The type of numbers.
%  
%
%Arithmetic operations
%=====================
%  
%<<
%  val (+/) : num -> num -> num
%>>
%    
%                Same as Num.add_num[22.1].
%  
%<<
%  val add_num : num -> num -> num
%>>
%    
%                Addition
%  
%<<
%  val minus_num : num -> num
%>>
%    
%                Unary negation.
%  
%<<
%  val (-/) : num -> num -> num
%>>
%    
%                Same as Num.sub_num[22.1].
%  
%<<
%  val sub_num : num -> num -> num
%>>
%    
%                Subtraction
%  
%<<
%  val (*/) : num -> num -> num
%>>
%    
%                Same as Num.mult_num[22.1].
%  
%<<
%  val mult_num : num -> num -> num
%>>
%    
%                Multiplication
%  
%<<
%  val square_num : num -> num
%>>
%    
%                Squaring
%  
%<<
%  val (//) : num -> num -> num
%>>
%    
%                Same as Num.div_num[22.1].
%  
%<<
%  val div_num : num -> num -> num
%>>
%    
%                Division
%  
%<<
%  val quo_num : num -> num -> num
%>>
%    
%                Euclidean division: quotient.
%  
%<<
%  val mod_num : num -> num -> num
%>>
%    
%                Euclidean division: remainder.
%  
%<<
%  val (**/) : num -> num -> num
%>>
%    
%                Same as Num.power_num[22.1].
%  
%<<
%  val power_num : num -> num -> num
%>>
%    
%                Exponentiation
%  
%<<
%  val abs_num : num -> num
%>>
%    
%                Absolute value.
%  
%<<
%  val succ_num : num -> num
%>>
%    
%                succ n is n+1
%  
%<<
%  val pred_num : num -> num
%>>
%    
%                pred n is n-1
%  
%<<
%  val incr_num : num Pervasives.ref -> unit
%>>
%    
%                incr r is r:=!r+1, where r is a reference to a number.
%  
%<<
%  val decr_num : num Pervasives.ref -> unit
%>>
%    
%                decr r is r:=!r-1, where r is a reference to a number.
%  
%<<
%  val is_integer_num : num -> bool
%>>
%    
%                Test if a number is an integer
%  
%  The four following functions approximate a number by an integer :
%<<
%  val integer_num : num -> num
%>>
%    
%                integer_num n returns the integer closest to n. In case of
%               ties,   rounds towards zero.
%  
%<<
%  val floor_num : num -> num
%>>
%    
%                floor_num n returns the largest integer smaller or equal to n.
%  
%<<
%  val round_num : num -> num
%>>
%    
%                round_num n returns the integer closest to n. In case of ties, 
%               rounds off zero.
%  
%<<
%  val ceiling_num : num -> num
%>>
%    
%                ceiling_num n returns the smallest integer bigger or equal to
%               n.
%  
%<<
%  val sign_num : num -> int
%>>
%    
%                Return -1, 0 or 1 according to the sign of the argument.
%  
%
%Comparisons between numbers
%---------------------------
%  
%<<
%  val (=/) : num -> num -> bool
%>>
%   
%<<
%  val (</) : num -> num -> bool
%>>
%   
%<<
%  val (>/) : num -> num -> bool
%>>
%   
%<<
%  val (<=/) : num -> num -> bool
%>>
%   
%<<
%  val (>=/) : num -> num -> bool
%>>
%   
%<<
%  val (<>/) : num -> num -> bool
%>>
%   
%<<
%  val eq_num : num -> num -> bool
%>>
%   
%<<
%  val lt_num : num -> num -> bool
%>>
%   
%<<
%  val le_num : num -> num -> bool
%>>
%   
%<<
%  val gt_num : num -> num -> bool
%>>
%   
%<<
%  val ge_num : num -> num -> bool
%>>
%   
%<<
%  val compare_num : num -> num -> int
%>>
%    
%                Return -1, 0 or 1 if the first argument is less than,  equal
%               to, or greater than the second argument.
%  
%<<
%  val max_num : num -> num -> num
%>>
%    
%                Return the greater of the two arguments.
%  
%<<
%  val min_num : num -> num -> num
%>>
%    
%                Return the smaller of the two arguments.
%  
%
%Coercions with strings
%======================
%  
%<<
%  val string_of_num : num -> string
%>>
%    
%                Convert a number to a string, using fractional notation.
%  
%<<
%  val approx_num_fix : int -> num -> string
%>>
%    
%                See Num.approx_num_exp[22.1].
%  
%<<
%  val approx_num_exp : int -> num -> string
%>>
%    
%                Approximate a number by a decimal. The first argument is the 
%               required precision. The second argument is the number to 
%               approximate. Num.approx_num_fix[22.1] uses decimal notation; the
%               first  argument is the number of digits after the decimal point.
%                approx_num_exp uses scientific (exponential) notation; the 
%               first argument is the number of digits in the mantissa.
%  
%<<
%  val num_of_string : string -> num
%>>
%    
%                Convert a string to a number.
%  
%
%Coercions between numerical types
%=================================
%  
%<<
%  val int_of_num : num -> int
%>>
%   
%<<
%  val num_of_int : int -> num
%>>
%   
%<<
%  val nat_of_num : num -> Nat.nat
%>>
%   
%<<
%  val num_of_nat : Nat.nat -> num
%>>
%   
%<<
%  val num_of_big_int : Big_int.big_int -> num
%>>
%   
%<<
%  val big_int_of_num : num -> Big_int.big_int
%>>
%   
%<<
%  val ratio_of_num : num -> Ratio.ratio
%>>
%   
%<<
%  val num_of_ratio : Ratio.ratio -> num
%>>
%   
%<<
%  val float_of_num : num -> float
%>>
%   
%
%
%22.2  Module Big_int : Operations on arbitrary-precision integers.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  Big integers (type big_int) are signed integers of arbitrary size.
%  0.5cm
%<<
%  type big_int 
%>>
%    
%                The type of big integers.
%  
%<<
%  val zero_big_int : big_int
%>>
%    
%                The big integer 0.
%  
%<<
%  val unit_big_int : big_int
%>>
%    
%                The big integer 1.
%  
%
%Arithmetic operations
%=====================
%  
%<<
%  val minus_big_int : big_int -> big_int
%>>
%    
%                Unary negation.
%  
%<<
%  val abs_big_int : big_int -> big_int
%>>
%    
%                Absolute value.
%  
%<<
%  val add_big_int : big_int -> big_int -> big_int
%>>
%    
%                Addition.
%  
%<<
%  val succ_big_int : big_int -> big_int
%>>
%    
%                Successor (add 1).
%  
%<<
%  val add_int_big_int : int -> big_int -> big_int
%>>
%    
%                Addition of a small integer to a big integer.
%  
%<<
%  val sub_big_int : big_int -> big_int -> big_int
%>>
%    
%                Subtraction.
%  
%<<
%  val pred_big_int : big_int -> big_int
%>>
%    
%                Predecessor (subtract 1).
%  
%<<
%  val mult_big_int : big_int -> big_int -> big_int
%>>
%    
%                Multiplication of two big integers.
%  
%<<
%  val mult_int_big_int : int -> big_int -> big_int
%>>
%    
%                Multiplication of a big integer by a small integer
%  
%<<
%  val square_big_int : big_int -> big_int
%>>
%    
%                Return the square of the given big integer
%  
%<<
%  val sqrt_big_int : big_int -> big_int
%>>
%    
%                sqrt_big_int a returns the integer square root of a,  that is,
%               the largest big integer r such that r * r <= a.  Raise
%               Invalid_argument if a is negative.
%  
%<<
%  val quomod_big_int : big_int -> big_int -> big_int * big_int
%>>
%    
%                Euclidean division of two big integers.  The first part of the
%               result is the quotient,  the second part is the remainder. 
%               Writing (q,r) = quomod_big_int a b, we have  a = q * b + r and 0
%               <= r < |b|.  Raise Division_by_zero if the divisor is zero.
%  
%<<
%  val div_big_int : big_int -> big_int -> big_int
%>>
%    
%                Euclidean quotient of two big integers.  This is the first
%               result q of quomod_big_int (see above).
%  
%<<
%  val mod_big_int : big_int -> big_int -> big_int
%>>
%    
%                Euclidean modulus of two big integers.  This is the second
%               result r of quomod_big_int (see above).
%  
%<<
%  val gcd_big_int : big_int -> big_int -> big_int
%>>
%    
%                Greatest common divisor of two big integers.
%  
%<<
%  val power_int_positive_int : int -> int -> big_int
%>>
%   
%<<
%  val power_big_int_positive_int : big_int -> int -> big_int
%>>
%   
%<<
%  val power_int_positive_big_int : int -> big_int -> big_int
%>>
%   
%<<
%  val power_big_int_positive_big_int : big_int -> big_int -> big_int
%>>
%    
%                Exponentiation functions. Return the big integer  representing
%               the first argument a raised to the power b  (the second
%               argument). Depending  on the function, a and b can be either
%               small integers  or big integers. Raise Invalid_argument if b is
%               negative.
%  
%
%Comparisons and tests
%=====================
%  
%<<
%  val sign_big_int : big_int -> int
%>>
%    
%                Return 0 if the given big integer is zero,  1 if it is
%               positive, and -1 if it is negative.
%  
%<<
%  val compare_big_int : big_int -> big_int -> int
%>>
%    
%                compare_big_int a b returns 0 if a and b are equal,  1 if a is
%               greater than b, and -1 if a is smaller  than b.
%  
%<<
%  val eq_big_int : big_int -> big_int -> bool
%>>
%   
%<<
%  val le_big_int : big_int -> big_int -> bool
%>>
%   
%<<
%  val ge_big_int : big_int -> big_int -> bool
%>>
%   
%<<
%  val lt_big_int : big_int -> big_int -> bool
%>>
%   
%<<
%  val gt_big_int : big_int -> big_int -> bool
%>>
%    
%                Usual boolean comparisons between two big integers.
%  
%<<
%  val max_big_int : big_int -> big_int -> big_int
%>>
%    
%                Return the greater of its two arguments.
%  
%<<
%  val min_big_int : big_int -> big_int -> big_int
%>>
%    
%                Return the smaller of its two arguments.
%  
%<<
%  val num_digits_big_int : big_int -> int
%>>
%    
%                Return the number of machine words used to store the  given big
%               integer.
%  
%
%Conversions to and from strings
%===============================
%  
%<<
%  val string_of_big_int : big_int -> string
%>>
%    
%                Return the string representation of the given big integer,  in
%               decimal (base 10).
%  
%<<
%  val big_int_of_string : string -> big_int
%>>
%    
%                Convert a string to a big integer, in decimal.  The string
%               consists of an optional - or + sign,  followed by one or several
%               decimal digits.
%  
%
%Conversions to and from other numerical types
%=============================================
%  
%<<
%  val big_int_of_int : int -> big_int
%>>
%    
%                Convert a small integer to a big integer.
%  
%<<
%  val is_int_big_int : big_int -> bool
%>>
%    
%                Test whether the given big integer is small enough to  be
%               representable as a small integer (type int)  without loss of
%               precision. On a 32'bit platform,  is_int_big_int a returns true
%               if and only if  a is between 2^30 and 2^30-1. On a 64'bit
%               platform,  is_int_big_int a returns true if and only if  a is
%               between -2^62 and 2^62-1.
%  
%<<
%  val int_of_big_int : big_int -> int
%>>
%    
%                Convert a big integer to a small integer (type int).  Raises
%               Failure "int_of_big_int" if the big integer  is not
%               representable as a small integer.
%  
%<<
%  val float_of_big_int : big_int -> float
%>>
%    
%                Returns a floating-point number approximating the  given big
%               integer.
%  
%
%
%22.3  Module Arith_status : Flags that control rational arithmetic.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%<<
%  val arith_status : unit -> unit
%>>
%    
%                Print the current status of the arithmetic flags.
%  
%<<
%  val get_error_when_null_denominator : unit -> bool
%>>
%    
%                See Arith_status.set_error_when_null_denominator[22.3].
%  
%<<
%  val set_error_when_null_denominator : bool -> unit
%>>
%    
%                Get or set the flag null_denominator. When on, attempting to  
%               create a rational with a null denominator raises an exception. 
%               When off, rationals with null denominators are accepted. 
%               Initially: on.
%  
%<<
%  val get_normalize_ratio : unit -> bool
%>>
%    
%                See Arith_status.set_normalize_ratio[22.3].
%  
%<<
%  val set_normalize_ratio : bool -> unit
%>>
%    
%                Get or set the flag normalize_ratio. When on, rational  numbers
%               are normalized after each operation. When off,  rational numbers
%               are not normalized until printed.  Initially: off.
%  
%<<
%  val get_normalize_ratio_when_printing : unit -> bool
%>>
%    
%                See Arith_status.set_normalize_ratio_when_printing[22.3].
%  
%<<
%  val set_normalize_ratio_when_printing : bool -> unit
%>>
%    
%                Get or set the flag normalize_ratio_when_printing.  When on,
%               rational numbers are normalized before being printed.  When off,
%               rational numbers are printed as is, without normalization. 
%               Initially: on.
%  
%<<
%  val get_approx_printing : unit -> bool
%>>
%    
%                See Arith_status.set_approx_printing[22.3].
%  
%<<
%  val set_approx_printing : bool -> unit
%>>
%    
%                Get or set the flag approx_printing.  When on, rational numbers
%               are printed as a decimal approximation.  When off, rational
%               numbers are printed as a fraction.  Initially: off.
%  
%<<
%  val get_floating_precision : unit -> int
%>>
%    
%                See Arith_status.set_floating_precision[22.3].
%  
%<<
%  val set_floating_precision : int -> unit
%>>
%    
%                Get or set the parameter floating_precision.  This parameter is
%               the number of digits displayed when  approx_printing is on. 
%               Initially: 12.
%  
%   
%   
%  
%
%Chapter 23    The str library: regular expressions and string processing
%************************************************************************
%   
%  The str library provides high-level string processing functions, some based
%on regular expressions. It is intended to support the kind of file processing
%that is usually performed with scripting languages such as awk, perl or sed.
%  Programs that use the str library must be linked as follows: 
%<<
%          ocamlc other options str.cma other files
%          ocamlopt other options str.cmxa other files
%>>
%   For interactive use of the str library, do: 
%<<
%          ocamlmktop -o mytop str.cma
%          ./mytop
%>>
%   or (if dynamic linking of C libraries is supported on your platform), start
%ocaml and type #load "str.cma";;.
%  
%
%23.1  Module Str : Regular expressions and high-level string processing
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  0.5cm
%
%Regular expressions
%===================
%  
%<<
%  type regexp 
%>>
%    
%                The type of compiled regular expressions.
%  
%<<
%  val regexp : string -> regexp
%>>
%    
%                Compile a regular expression. The following constructs are 
%               recognized:
%                 
%                - .  Matches any character except newline. 
%                - *  (postfix) Matches the preceding expression zero, one or 
%                  several times 
%                - +  (postfix) Matches the preceding expression one or  several
%                  times 
%                - ?  (postfix) Matches the preceding expression once or  not at
%                  all 
%                - [..]  Character set. Ranges are denoted with -, as in [a-z]. 
%                  An initial ^, as in [^0-9], complements the set.  To include
%                  a ] character in a set, make it the first  character of the
%                  set. To include a - character in a set,  make it the first or
%                  the last character of the set. 
%                - ^ Matches at beginning of line (either at the beginning of 
%                  the matched string, or just after a newline character). 
%                - $  Matches at end of line (either at the end of the matched 
%                  string, or just before a newline character). 
%                - \|  (infix) Alternative between two expressions. 
%                - \(..\) Grouping and naming of the enclosed expression. 
%                - \1  The text matched by the first \(...\) expression  (\2 for
%                  the second expression, and so on up to \9). 
%                - \b  Matches word boundaries. 
%                - \  Quotes special characters. The special characters  are
%                  $^.*+?[]. 
%  
%<<
%  val regexp_case_fold : string -> regexp
%>>
%    
%                Same as regexp, but the compiled expression will match text  in
%               a case-insensitive way: uppercase and lowercase letters will  be
%               considered equivalent.
%  
%<<
%  val quote : string -> string
%>>
%    
%                Str.quote s returns a regexp string that matches exactly  s and
%               nothing else.
%  
%<<
%  val regexp_string : string -> regexp
%>>
%    
%                Str.regexp_string s returns a regular expression  that matches
%               exactly s and nothing else.
%  
%<<
%  val regexp_string_case_fold : string -> regexp
%>>
%    
%                Str.regexp_string_case_fold is similar to
%               Str.regexp_string[23.1],   but the regexp matches in a
%               case-insensitive way.
%  
%
%String matching and searching
%=============================
%  
%<<
%  val string_match : regexp -> string -> int -> bool
%>>
%    
%                string_match r s start tests whether a substring of s that 
%               starts at position start matches the regular expression r.  The
%               first character of a string has position 0, as usual.
%  
%<<
%  val search_forward : regexp -> string -> int -> int
%>>
%    
%                search_forward r s start searches the string s for a substring 
%               matching the regular expression r. The search starts at position
%                start and proceeds towards the end of the string.  Return the
%               position of the first character of the matched  substring, or
%               raise Not_found if no substring matches.
%  
%<<
%  val search_backward : regexp -> string -> int -> int
%>>
%    
%                search_backward r s last searches the string s for a  substring
%               matching the regular expression r. The search first  considers
%               substrings that start at position last and proceeds  towards the
%               beginning of string. Return the position of the first  character
%               of the matched substring; raise Not_found if no  substring
%               matches.
%  
%<<
%  val string_partial_match : regexp -> string -> int -> bool
%>>
%    
%                Similar to Str.string_match[23.1], but also returns true if 
%               the argument string is a prefix of a string that matches.  This
%               includes the case of a true complete match.
%  
%<<
%  val matched_string : string -> string
%>>
%    
%                matched_string s returns the substring of s that was matched 
%               by the latest Str.string_match[23.1], Str.search_forward[23.1]
%               or   Str.search_backward[23.1].  The user must make sure that
%               the parameter s is the same string  that was passed to the
%               matching or searching function.
%  
%<<
%  val match_beginning : unit -> int
%>>
%    
%                match_beginning() returns the position of the first character 
%               of the substring that was matched by Str.string_match[23.1], 
%               Str.search_forward[23.1] or Str.search_backward[23.1].
%  
%<<
%  val match_end : unit -> int
%>>
%    
%                match_end() returns the position of the character following the
%                 last character of the substring that was matched by
%               string_match,  search_forward or search_backward.
%  
%<<
%  val matched_group : int -> string -> string
%>>
%    
%                matched_group n s returns the substring of s that was matched 
%               by the nth group \(...\) of the regular expression during  the
%               latest Str.string_match[23.1], Str.search_forward[23.1] or  
%               Str.search_backward[23.1].  The user must make sure that the
%               parameter s is the same string  that was passed to the matching
%               or searching function.  matched_group n s raises Not_found if
%               the nth group  of the regular expression was not matched. This
%               can happen  with groups inside alternatives \|, options ?  or
%               repetitions *. For instance, the empty string will match 
%               \(a\)*, but matched_group 1 "" will raise Not_found  because the
%               first group itself was not matched.
%  
%<<
%  val group_beginning : int -> int
%>>
%    
%                group_beginning n returns the position of the first character 
%               of the substring that was matched by the nth group of  the
%               regular expression.
%               Raises 
%                 
%                - Not_found if the nth group of the regular expression  was not
%                  matched. 
%                - Invalid_argument if there are fewer than n groups in  the
%                  regular expression. 
%  
%<<
%  val group_end : int -> int
%>>
%    
%                group_end n returns  the position of the character following
%               the last character of  substring that was matched by the nth
%               group of the regular expression.
%               Raises 
%                 
%                - Not_found if the nth group of the regular expression  was not
%                  matched. 
%                - Invalid_argument if there are fewer than n groups in  the
%                  regular expression. 
%  
%
%Replacement
%===========
%  
%<<
%  val global_replace : regexp -> string -> string -> string
%>>
%    
%                global_replace regexp templ s returns a string identical to s, 
%               except that all substrings of s that match regexp have been 
%               replaced by templ. The replacement template templ can contain 
%               \1, \2, etc; these sequences will be replaced by the text 
%               matched by the corresponding group in the regular expression. 
%               \0 stands for the text matched by the whole regular expression.
%  
%<<
%  val replace_first : regexp -> string -> string -> string
%>>
%    
%                Same as Str.global_replace[23.1], except that only the first
%               substring  matching the regular expression is replaced.
%  
%<<
%  val global_substitute : regexp -> (string -> string) -> string -> string
%>>
%    
%                global_substitute regexp subst s returns a string identical  to
%               s, except that all substrings of s that match regexp  have been
%               replaced by the result of function subst. The  function subst is
%               called once for each matching substring,  and receives s (the
%               whole text) as argument.
%  
%<<
%  val substitute_first : regexp -> (string -> string) -> string -> string
%>>
%    
%                Same as Str.global_substitute[23.1], except that only the first
%               substring  matching the regular expression is replaced.
%  
%<<
%  val replace_matched : string -> string -> string
%>>
%    
%                replace_matched repl s returns the replacement text repl  in
%               which \1, \2, etc. have been replaced by the text  matched by
%               the corresponding groups in the most recent matching  operation.
%               s must be the same string that was matched during  this matching
%               operation.
%  
%
%Splitting
%=========
%  
%<<
%  val split : regexp -> string -> string list
%>>
%    
%                split r s splits s into substrings, taking as delimiters  the
%               substrings that match r, and returns the list of substrings. 
%               For instance, split (regexp "[ \t]+") s splits s into 
%               blank-separated words. An occurrence of the delimiter at the 
%               beginning and at the end of the string is ignored.
%  
%<<
%  val bounded_split : regexp -> string -> int -> string list
%>>
%    
%                Same as Str.split[23.1], but splits into at most n substrings, 
%               where n is the extra integer parameter.
%  
%<<
%  val split_delim : regexp -> string -> string list
%>>
%    
%                Same as Str.split[23.1] but occurrences of the  delimiter at
%               the beginning and at the end of the string are  recognized and
%               returned as empty strings in the result.  For instance,
%               split_delim (regexp " ") " abc "  returns [""; "abc"; ""], while
%               split with the same  arguments returns ["abc"].
%  
%<<
%  val bounded_split_delim : regexp -> string -> int -> string list
%>>
%    
%                Same as Str.bounded_split[23.1], but occurrences of the 
%               delimiter at the beginning and at the end of the string are 
%               recognized and returned as empty strings in the result.
%  
%<<
%  type split_result =
%    | Text of string
%    | Delim of string
%>>
%   
%<<
%  val full_split : regexp -> string -> split_result list
%>>
%    
%                Same as Str.split_delim[23.1], but returns  the delimiters as
%               well as the substrings contained between  delimiters. The former
%               are tagged Delim in the result list;  the latter are tagged
%               Text. For instance,  full_split (regexp "[{}]") "{ab}" returns 
%               [Delim "{"; Text "ab"; Delim "}"].
%  
%<<
%  val bounded_full_split : regexp -> string -> int -> split_result list
%>>
%    
%                Same as Str.bounded_split_delim[23.1], but returns  the
%               delimiters as well as the substrings contained between 
%               delimiters. The former are tagged Delim in the result list;  the
%               latter are tagged Text.
%  
%
%Extracting substrings
%=====================
%  
%<<
%  val string_before : string -> int -> string
%>>
%    
%                string_before s n returns the substring of all characters of s 
%               that precede position n (excluding the character at  position
%               n).
%  
%<<
%  val string_after : string -> int -> string
%>>
%    
%                string_after s n returns the substring of all characters of s 
%               that follow position n (including the character at  position n).
%  
%<<
%  val first_chars : string -> int -> string
%>>
%    
%                first_chars s n returns the first n characters of s.  This is
%               the same function as Str.string_before[23.1].
%  
%<<
%  val last_chars : string -> int -> string
%>>
%    
%                last_chars s n returns the last n characters of s.
%  
%   
%   
%  
%
%dChapter 24    The threads library
%d*********************************
%    
%  The threads library allows concurrent programming in Objective Caml. It
%provides multiple threads of control (also called lightweight processes) that
%execute concurrently in the same memory space. Threads communicate by in-place
%modification of shared data structures, or by sending and receiving data on
%communication channels.
%  The threads library is implemented by time-sharing on a single processor. It
%will not take advantage of multi-processor machines. Using this library will
%therefore never make programs run faster. However, many programs are easier to
%write when structured as several communicating processes.
%  Two implementations of the threads library are available, depending on the
%capabilities of the operating system: 
%  
% - System threads. This implementation builds on the OS-provided threads
%   facilities: POSIX 1003.1c threads for Unix, and Win32 threads for Windows.
%   When available, system threads support both bytecode and native'code
%   programs. 
% - VM-level threads. This implementation performs time-sharing and context
%   switching at the level of the OCaml virtual machine (bytecode interpreter).
%   It is available on Unix systems, and supports only bytecode programs. It
%   cannot be used with native'code programs. 
%   Programs that use system threads must be linked as follows: 
%<<
%          ocamlc -thread other options threads.cma other files
%          ocamlopt -thread other options threads.cmxa other files
%>>
%   All object files on the command line must also have been compiled with the
%-thread option (see chapter 8).
%  Programs that use VM-level threads must be compiled with the -vmthread option
%to ocamlc (see chapter 8), and be linked as follows: 
%<<
%          ocamlc -vmthread other options threads.cma other files
%>>
%  
%  
%
%d24.1  Module Thread : Lightweight threads for Posix 1003.1c and Win32.
%d*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%d%
%d%   
%d%  0.5cm
%d%<<
%d  type t 
%d%>>
%d%    
%d%                The type of thread handles.
%d%  
%d%
%d%Thread creation and termination
%d%===============================
%d%  
%d%<<
%d  val create : ('a -> 'b) -> 'a -> t
%d%>>
%    
%                Thread.create funct arg creates a new thread of control,  in
%               which the function application funct arg  is executed
%               concurrently with the other threads of the program.  The
%               application of Thread.create  returns the handle of the newly
%               created thread.  The new thread terminates when the application
%               funct arg  returns, either normally or by raising an uncaught
%               exception.  In the latter case, the exception is printed on
%               standard error,  but not propagated back to the parent thread.
%               Similarly, the  result of the application funct arg is discarded
%               and not  directly accessible to the parent thread.
%  
%<<
%  val self : unit -> t
%>>
%    
%                Return the thread currently executing.
%  
%<<
%  val id : t -> int
%>>
%    
%                Return the identifier of the given thread. A thread identifier 
%               is an integer that identifies uniquely the thread.  It can be
%               used to build data structures indexed by threads.
%  
%<<
%  val exit : unit -> unit
%>>
%    
%                Terminate prematurely the currently executing thread.
%  
%<<
%  val kill : t -> unit
%>>
%    
%                Terminate prematurely the thread whose handle is given.
%  
%
%Suspending threads
%==================
%  
%<<
%  val delay : float -> unit
%>>
%    
%                delay d suspends the execution of the calling thread for  d
%               seconds. The other program threads continue to run during  this
%               time.
%  
%<<
%  val join : t -> unit
%>>
%    
%                join th suspends the execution of the calling thread  until the
%               thread th has terminated.
%  
%<<
%  val wait_read : Unix.file_descr -> unit
%>>
%    
%                See Thread.wait_write[24.1].
%  
%<<
%  val wait_write : Unix.file_descr -> unit
%>>
%    
%                This function does nothing in this implementation.
%  
%<<
%  val wait_timed_read : Unix.file_descr -> float -> bool
%>>
%    
%                See Thread.wait_timed_read[24.1].
%  
%<<
%  val wait_timed_write : Unix.file_descr -> float -> bool
%>>
%    
%                Suspend the execution of the calling thread until at least  one
%               character is available for reading (wait_read) or  one character
%               can be written without blocking (wait_write)  on the given Unix
%               file descriptor. Wait for at most  the amount of time given as
%               second argument (in seconds).  Return true if the file
%               descriptor is ready for input/output  and false if the timeout
%               expired. 
%               These functions return immediately true in the Win32 
%               implementation.
%  
%<<
%  val select :
%    Unix.file_descr list ->
%    Unix.file_descr list ->
%    Unix.file_descr list ->
%    float -> Unix.file_descr list * Unix.file_descr list * Unix.file_descr list
%>>
%    
%                Suspend the execution of the calling thead until input/output 
%               becomes possible on the given Unix file descriptors.  The
%               arguments and results have the same meaning as for  Unix.select.
%                This function is not implemented yet under Win32.
%  
%<<
%  val wait_pid : int -> int * Unix.process_status
%>>
%    
%                wait_pid p suspends the execution of the calling thread  until
%               the process specified by the process identifier p  terminates.
%               Returns the pid of the child caught and  its termination status,
%               as per Unix.wait.  This function is not implemented under MacOS.
%  
%<<
%  val wait_signal : int list -> int
%>>
%    
%                wait_signal sigs suspends the execution of the calling thread 
%               until the process receives one of the signals specified in the 
%               list sigs. It then returns the number of the signal received. 
%               Signal handlers attached to the signals in sigs will not  be
%               invoked. Do not call wait_signal concurrently   from several
%               threads on the same signals.
%  
%<<
%  val yield : unit -> unit
%>>
%    
%                Re-schedule the calling thread without suspending it.  This
%               function can be used to give scheduling hints,  telling the
%               scheduler that now is a good time to  switch to other threads.
%  
%
%
%24.2  Module Mutex : Locks for mutual exclusion.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  Mutexes (mutual-exclusion locks) are used to implement critical sections  and
%protect shared mutable data structures against concurrent accesses.  The
%typical use is (if m is the mutex associated with the data structure  D):  
%<<
%  
%       Mutex.lock m;
%       (* Critical section that operates over D *);
%       Mutex.unlock m
%     
%>>
%  
%  0.5cm
%<<
%  type t 
%>>
%    
%                The type of mutexes.
%  
%<<
%  val create : unit -> t
%>>
%    
%                Return a new mutex.
%  
%<<
%  val lock : t -> unit
%>>
%    
%                Lock the given mutex. Only one thread can have the mutex locked
%                at any time. A thread that attempts to lock a mutex already
%               locked  by another thread will suspend until the other thread
%               unlocks  the mutex.
%  
%<<
%  val try_lock : t -> bool
%>>
%    
%                Same as Mutex.lock[24.2], but does not suspend the calling
%               thread if  the mutex is already locked: just return false
%               immediately  in that case. If the mutex is unlocked, lock it and
%                return true.
%  
%<<
%  val unlock : t -> unit
%>>
%    
%                Unlock the given mutex. Other threads suspended trying to lock 
%               the mutex will restart.
%  
%
%
%24.3  Module Condition : Condition variables to synchronize between threads.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  Condition variables are used when one thread wants to wait until another 
%thread has finished doing something: the former thread --waits-- on the 
%condition variable, the latter thread --signals-- the condition when it  is
%done. Condition variables should always be protected by a mutex.  The typical
%use is (if D is a shared data structure, m its mutex,  and c is a condition
%variable):  
%<<
%  
%       Mutex.lock m;
%       while (* some predicate P over D is not satisfied *) do
%         Condition.wait c m
%       done;
%       (* Modify D *)
%       if (* the predicate P over D is now satified *) then Condition.signal c;
%       Mutex.unlock m
%     
%>>
%  
%  0.5cm
%<<
%  type t 
%>>
%    
%                The type of condition variables.
%  
%<<
%  val create : unit -> t
%>>
%    
%                Return a new condition variable.
%  
%<<
%  val wait : t -> Mutex.t -> unit
%>>
%    
%                wait c m atomically unlocks the mutex m and suspends the 
%               calling process on the condition variable c. The process will 
%               restart after the condition variable c has been signalled.  The
%               mutex m is locked again before wait returns.
%  
%<<
%  val signal : t -> unit
%>>
%    
%                signal c restarts one of the processes waiting on the  
%               condition variable c.
%  
%<<
%  val broadcast : t -> unit
%>>
%    
%                broadcast c restarts all processes waiting on the   condition
%               variable c.
%  
%
%
%24.4  Module Event : First'class synchronous communication.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  This module implements synchronous inter-thread communications over 
%channels. As in John Reppy-s Concurrent ML system, the communication   events
%are first'class values: they can be built and combined  independently before
%being offered for communication.
%  0.5cm
%<<
%  type 'a channel 
%>>
%    
%                The type of communication channels carrying values of type 'a.
%  
%<<
%  val new_channel : unit -> 'a channel
%>>
%    
%                Return a new channel.
%  
%<<
%  type 'a event 
%>>
%    
%                The type of communication events returning a result of type 'a.
%  
%<<
%  val send : 'a channel -> 'a -> unit event
%>>
%    
%                send ch v returns the event consisting in sending the value v 
%               over the channel ch. The result value of this event is ().
%  
%<<
%  val receive : 'a channel -> 'a event
%>>
%    
%                receive ch returns the event consisting in receiving a value 
%               from the channel ch. The result value of this event is the 
%               value received.
%  
%<<
%  val always : 'a -> 'a event
%>>
%    
%                always v returns an event that is always ready for 
%               synchronization. The result value of this event is v.
%  
%<<
%  val choose : 'a event list -> 'a event
%>>
%    
%                choose evl returns the event that is the alternative of  all
%               the events in the list evl.
%  
%<<
%  val wrap : 'a event -> ('a -> 'b) -> 'b event
%>>
%    
%                wrap ev fn returns the event that performs the same
%               communications  as ev, then applies the post-processing function
%               fn  on the return value.
%  
%<<
%  val wrap_abort : 'a event -> (unit -> unit) -> 'a event
%>>
%    
%                wrap_abort ev fn returns the event that performs  the same
%               communications as ev, but if it is not selected  the function fn
%               is called after the synchronization.
%  
%<<
%  val guard : (unit -> 'a event) -> 'a event
%>>
%    
%                guard fn returns the event that, when synchronized, computes 
%               fn() and behaves as the resulting event. This allows to  compute
%               events with side-effects at the time of the synchronization 
%               operation.
%  
%<<
%  val sync : 'a event -> 'a
%>>
%    
%                --Synchronize-- on an event: offer all the communication  
%               possibilities specified in the event to the outside world,  and
%               block until one of the communications succeed. The result  value
%               of that communication is returned.
%  
%<<
%  val select : 'a event list -> 'a
%>>
%    
%                --Synchronize-- on an alternative of events.  select evl is
%               shorthand for sync(choose evl).
%  
%<<
%  val poll : 'a event -> 'a option
%>>
%    
%                Non'blocking version of Event.sync[24.4]: offer all the
%               communication   possibilities specified in the event to the
%               outside world,  and if one can take place immediately, perform
%               it and return  Some r where r is the result value of that
%               communication.  Otherwise, return None without blocking.
%  
%
%
%24.5  Module ThreadUnix : Thread'compatible system calls.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%    The functionality of this module has been merged back into  the Unix[21.1]
%module. Threaded programs can now call the functions  from module Unix[21.1]
%directly, and still get the correct behavior  (block the calling thread, if
%required, but do not block all threads  in the process).Thread'compatible
%system calls.
%  0.5cm
%
%Process handling
%================
%  
%<<
%  val execv : string -> string array -> unit
%>>
%   
%<<
%  val execve : string -> string array -> string array -> unit
%>>
%   
%<<
%  val execvp : string -> string array -> unit
%>>
%   
%<<
%  val wait : unit -> int * Unix.process_status
%>>
%   
%<<
%  val waitpid : Unix.wait_flag list -> int -> int * Unix.process_status
%>>
%   
%<<
%  val system : string -> Unix.process_status
%>>
%
%
%Basic input/output
%==================
%  
%<<
%  val read : Unix.file_descr -> string -> int -> int -> int
%>>
%   
%<<
%  val write : Unix.file_descr -> string -> int -> int -> int
%>>
%
%
%Input/output with timeout
%=========================
%  
%<<
%  val timed_read : Unix.file_descr -> string -> int -> int -> float -> int
%>>
%    
%                See ThreadUnix.timed_write[24.5].
%  
%<<
%  val timed_write : Unix.file_descr -> string -> int -> int -> float -> int
%>>
%    
%                Behave as ThreadUnix.read[24.5] and ThreadUnix.write[24.5],
%               except that  Unix_error(ETIMEDOUT,_,_) is raised if no data is 
%               available for reading or ready for writing after d seconds.  The
%               delay d is given in the fifth argument, in seconds.
%  
%
%Polling
%=======
%  
%<<
%  val select :
%    Unix.file_descr list ->
%    Unix.file_descr list ->
%    Unix.file_descr list ->
%    float -> Unix.file_descr list * Unix.file_descr list * Unix.file_descr list
%>>
%
%
%Pipes and redirections
%======================
%  
%<<
%  val pipe : unit -> Unix.file_descr * Unix.file_descr
%>>
%   
%<<
%  val open_process_in : string -> Pervasives.in_channel
%>>
%   
%<<
%  val open_process_out : string -> Pervasives.out_channel
%>>
%   
%<<
%  val open_process : string -> Pervasives.in_channel * Pervasives.out_channel
%>>
%
%
%Time
%====
%  
%<<
%  val sleep : int -> unit
%>>
%
%
%Sockets
%=======
%  
%<<
%  val socket : Unix.socket_domain -> Unix.socket_type -> int -> Unix.file_descr
%>>
%   
%<<
%  val accept : Unix.file_descr -> Unix.file_descr * Unix.sockaddr
%>>
%   
%<<
%  val connect : Unix.file_descr -> Unix.sockaddr -> unit
%>>
%   
%<<
%  val recv :
%    Unix.file_descr -> string -> int -> int -> Unix.msg_flag list -> int
%>>
%   
%<<
%  val recvfrom :
%    Unix.file_descr ->
%    string -> int -> int -> Unix.msg_flag list -> int * Unix.sockaddr
%>>
%   
%<<
%  val send :
%    Unix.file_descr -> string -> int -> int -> Unix.msg_flag list -> int
%>>
%   
%<<
%  val sendto :
%    Unix.file_descr ->
%    string -> int -> int -> Unix.msg_flag list -> Unix.sockaddr -> int
%>>
%   
%<<
%  val open_connection :
%    Unix.sockaddr -> Pervasives.in_channel * Pervasives.out_channel
%>>
%   
%    
%  
%
%Chapter 25    The graphics library
%**********************************
%   
%  The graphics library provides a set of portable drawing primitives. Drawing
%takes place in a separate window that is created when open_graph is called.
%     Unix: 
%                This library is implemented under the X11 windows system. 
%               Programs that use the graphics library must be linked as
%               follows: 
%               <<
%                         ocamlc other options graphics.cma other files
%               >>
%                For interactive use of the graphics library, do: 
%               <<
%                         ocamlmktop -o mytop graphics.cma
%                         ./mytop
%               >>
%                or (if dynamic linking of C libraries is supported on your
%               platform), start ocaml and type #load "graphics.cma";;.
%               Here are the graphics mode specifications supported by
%               open_graph on the X11 implementation of this library: the
%               argument to open_graph has the format "display-name geometry",
%               where display-name is the name of the X-windows display to
%               connect to, and geometry is a standard X-windows geometry
%               specification. The two components are separated by a space.
%               Either can be omitted, or both. Examples: 
%                 
%                open_graph "foo:0"  connects to the display foo:0 and creates a
%                  window with the default geometry 
%                open_graph "foo:0 300x100+50-0"  connects to the display foo:0
%                  and creates a window 300 pixels wide by 100 pixels tall, at
%                  location (50,0) 
%                open_graph " 300x100+50-0"  connects to the default display and
%                  creates a window 300 pixels wide by 100 pixels tall, at
%                  location (50,0) 
%                open_graph ""  connects to the default display and creates a
%                  window with the default geometry. 
%                
%  
%     Windows: 
%                This library is available both for standalone compiled programs
%               and under the toplevel application ocamlwin.exe. For the latter,
%               this library must be loaded in'core by typing 
%               <<
%                         #load "graphics.cma";;
%               >>
%  
%  The screen coordinates are interpreted as shown in the figure below. Notice
%that the coordinate system used is the same as in mathematics: y increases from
%the bottom of the screen to the top of the screen, and angles are measured
%counterclockwise (in degrees). Drawing is clipped to the screen. 
%   
%                                 *libgraph.gif* 
%    
%  
%
%25.1  Module Graphics : Machine-independent graphics primitives.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  exception Graphic_failure of string
%>>
%    
%                Raised by the functions below when they encounter an error.
%  
%
%Initializations
%===============
%  
%<<
%  val open_graph : string -> unit
%>>
%    
%                Show the graphics window or switch the screen to graphic mode. 
%               The graphics window is cleared and the current point is set  to
%               (0, 0). The string argument is used to pass optional 
%               information on the desired graphics mode, the graphics window 
%               size, and so on. Its interpretation is implementation-dependent.
%                If the empty string is given, a sensible default is selected.
%  
%<<
%  val close_graph : unit -> unit
%>>
%    
%                Delete the graphics window or switch the screen back to text
%               mode.
%  
%<<
%  val set_window_title : string -> unit
%>>
%    
%                Set the title of the graphics window.
%  
%<<
%  val resize_window : int -> int -> unit
%>>
%    
%                Resize and erase the graphics window.
%  
%<<
%  val clear_graph : unit -> unit
%>>
%    
%                Erase the graphics window.
%  
%<<
%  val size_x : unit -> int
%>>
%    
%                See Graphics.size_y[25.1].
%  
%<<
%  val size_y : unit -> int
%>>
%    
%                Return the size of the graphics window. Coordinates of the
%               screen  pixels range over 0 .. size_x()-1 and 0 .. size_y()-1. 
%               Drawings outside of this rectangle are clipped, without causing 
%               an error. The origin (0,0) is at the lower left corner.
%  
%
%Colors
%======
%  
%<<
%  type color = int 
%>>
%    
%                A color is specified by its R, G, B components. Each component 
%               is in the range 0..255. The three components are packed in  an
%               int: 0xRRGGBB, where RR are the two hexadecimal digits for  the
%               red component, GG for the green component, BB for the  blue
%               component.
%  
%<<
%  val rgb : int -> int -> int -> color
%>>
%    
%                rgb r g b returns the integer encoding the color with red 
%               component r, green component g, and blue component b.  r, g and
%               b are in the range 0..255.
%  
%<<
%  val set_color : color -> unit
%>>
%    
%                Set the current drawing color.
%  
%<<
%  val background : color
%>>
%    
%                See Graphics.foreground[25.1].
%  
%<<
%  val foreground : color
%>>
%    
%                Default background and foreground colors (usually, either black
%                foreground on a white background or white foreground on a 
%               black background).  Graphics.clear_graph[25.1] fills the screen
%               with the background color.  The initial drawing color is
%               foreground.
%  
%
%Some predefined colors
%----------------------
%  
%<<
%  val black : color
%>>
%   
%<<
%  val white : color
%>>
%   
%<<
%  val red : color
%>>
%   
%<<
%  val green : color
%>>
%   
%<<
%  val blue : color
%>>
%   
%<<
%  val yellow : color
%>>
%   
%<<
%  val cyan : color
%>>
%   
%<<
%  val magenta : color
%>>
%
%
%Point and line drawing
%======================
%  
%<<
%  val plot : int -> int -> unit
%>>
%    
%                Plot the given point with the current drawing color.
%  
%<<
%  val plots : (int * int) array -> unit
%>>
%    
%                Plot the given points with the current drawing color.
%  
%<<
%  val point_color : int -> int -> color
%>>
%    
%                Return the color of the given point in the backing store  (see
%               "Double buffering" below).
%  
%<<
%  val moveto : int -> int -> unit
%>>
%    
%                Position the current point.
%  
%<<
%  val rmoveto : int -> int -> unit
%>>
%    
%                rmoveto dx dy translates the current point by the given vector.
%  
%<<
%  val current_x : unit -> int
%>>
%    
%                Return the abscissa of the current point.
%  
%<<
%  val current_y : unit -> int
%>>
%    
%                Return the ordinate of the current point.
%  
%<<
%  val current_point : unit -> int * int
%>>
%    
%                Return the position of the current point.
%  
%<<
%  val lineto : int -> int -> unit
%>>
%    
%                Draw a line with endpoints the current point and the given
%               point,  and move the current point to the given point.
%  
%<<
%  val rlineto : int -> int -> unit
%>>
%    
%                Draw a line with endpoints the current point and the  current
%               point translated of the given vector,  and move the current
%               point to this point.
%  
%<<
%  val curveto : int * int -> int * int -> int * int -> unit
%>>
%    
%                curveto b c d draws a cubic Bezier curve starting from  the
%               current point to point d, with control points b and  c, and
%               moves the current point to d.
%  
%<<
%  val draw_rect : int -> int -> int -> int -> unit
%>>
%    
%                draw_rect x y w h draws the rectangle with lower left corner 
%               at x,y, width w and height h.  The current point is unchanged. 
%               Raise Invalid_argument if w or h is negative.
%  
%<<
%  val draw_poly_line : (int * int) array -> unit
%>>
%    
%                draw_poly_line points draws the line that joins the  points
%               given by the array argument.  The array contains the coordinates
%               of the vertices of the  polygonal line, which need not be
%               closed.  The current point is unchanged.
%  
%<<
%  val draw_poly : (int * int) array -> unit
%>>
%    
%                draw_poly polygon draws the given polygon.  The array contains
%               the coordinates of the vertices of the  polygon.  The current
%               point is unchanged.
%  
%<<
%  val draw_segments : (int * int * int * int) array -> unit
%>>
%    
%                draw_segments segments draws the segments given in the array 
%               argument. Each segment is specified as a quadruple  (x0, y0, x1,
%               y1) where (x0, y0) and (x1, y1) are  the coordinates of the end
%               points of the segment.  The current point is unchanged.
%  
%<<
%  val draw_arc : int -> int -> int -> int -> int -> int -> unit
%>>
%    
%                draw_arc x y rx ry a1 a2 draws an elliptical arc with center 
%               x,y, horizontal radius rx, vertical radius ry, from angle  a1 to
%               angle a2 (in degrees). The current point is unchanged.  Raise
%               Invalid_argument if rx or ry is negative.
%  
%<<
%  val draw_ellipse : int -> int -> int -> int -> unit
%>>
%    
%                draw_ellipse x y rx ry draws an ellipse with center  x,y,
%               horizontal radius rx and vertical radius ry.  The current point
%               is unchanged.  Raise Invalid_argument if rx or ry is negative.
%  
%<<
%  val draw_circle : int -> int -> int -> unit
%>>
%    
%                draw_circle x y r draws a circle with center x,y and  radius r.
%               The current point is unchanged.  Raise Invalid_argument if r is
%               negative.
%  
%<<
%  val set_line_width : int -> unit
%>>
%    
%                Set the width of points and lines drawn with the functions
%               above.  Under X Windows, set_line_width 0 selects a width of 1
%               pixel  and a faster, but less precise drawing algorithm than the
%               one  used when set_line_width 1 is specified.  Raise
%               Invalid_argument if the argument is negative.
%  
%
%Text drawing
%============
%  
%<<
%  val draw_char : char -> unit
%>>
%    
%                See Graphics.draw_string[25.1].
%  
%<<
%  val draw_string : string -> unit
%>>
%    
%                Draw a character or a character string with lower left corner 
%               at current position. After drawing, the current position is set 
%               to the lower right corner of the text drawn.
%  
%<<
%  val set_font : string -> unit
%>>
%    
%                Set the font used for drawing text.  The interpretation of the
%               argument to set_font   is implementation-dependent.
%  
%<<
%  val set_text_size : int -> unit
%>>
%    
%                Set the character size used for drawing text.  The
%               interpretation of the argument to set_text_size   is
%               implementation-dependent.
%  
%<<
%  val text_size : string -> int * int
%>>
%    
%                Return the dimensions of the given text, if it were drawn with 
%               the current font and size.
%  
%
%Filling
%=======
%  
%<<
%  val fill_rect : int -> int -> int -> int -> unit
%>>
%    
%                fill_rect x y w h fills the rectangle with lower left corner 
%               at x,y, width w and height h, with the current color.  Raise
%               Invalid_argument if w or h is negative.
%  
%<<
%  val fill_poly : (int * int) array -> unit
%>>
%    
%                Fill the given polygon with the current color. The array 
%               contains the coordinates of the vertices of the polygon.
%  
%<<
%  val fill_arc : int -> int -> int -> int -> int -> int -> unit
%>>
%    
%                Fill an elliptical pie slice with the current color. The 
%               parameters are the same as for Graphics.draw_arc[25.1].
%  
%<<
%  val fill_ellipse : int -> int -> int -> int -> unit
%>>
%    
%                Fill an ellipse with the current color. The  parameters are the
%               same as for Graphics.draw_ellipse[25.1].
%  
%<<
%  val fill_circle : int -> int -> int -> unit
%>>
%    
%                Fill a circle with the current color. The  parameters are the
%               same as for Graphics.draw_circle[25.1].
%  
%
%Images
%======
%  
%<<
%  type image 
%>>
%    
%                The abstract type for images, in internal representation. 
%               Externally, images are represented as matrices of colors.
%  
%<<
%  val transp : color
%>>
%    
%                In matrices of colors, this color represent a --transparent-- 
%               point: when drawing the corresponding image, all pixels on the 
%               screen corresponding to a transparent pixel in the image will 
%               not be modified, while other points will be set to the color  of
%               the corresponding point in the image. This allows superimposing 
%               an image over an existing background.
%  
%<<
%  val make_image : color array array -> image
%>>
%    
%                Convert the given color matrix to an image.  Each sub'array
%               represents one horizontal line. All sub'arrays  must have the
%               same length; otherwise, exception Graphic_failure  is raised.
%  
%<<
%  val dump_image : image -> color array array
%>>
%    
%                Convert an image to a color matrix.
%  
%<<
%  val draw_image : image -> int -> int -> unit
%>>
%    
%                Draw the given image with lower left corner at the given point.
%  
%<<
%  val get_image : int -> int -> int -> int -> image
%>>
%    
%                Capture the contents of a rectangle on the screen as an image. 
%               The parameters are the same as for Graphics.fill_rect[25.1].
%  
%<<
%  val create_image : int -> int -> image
%>>
%    
%                create_image w h returns a new image w pixels wide and h 
%               pixels tall, to be used in conjunction with blit_image.  The
%               initial image contents are random, except that no point  is
%               transparent.
%  
%<<
%  val blit_image : image -> int -> int -> unit
%>>
%    
%                blit_image img x y copies screen pixels into the image img, 
%               modifying img in-place. The pixels copied are those inside the 
%               rectangle with lower left corner at x,y, and width and height 
%               equal to those of the image. Pixels that were transparent in 
%               img are left unchanged.
%  
%
%Mouse and keyboard events
%=========================
%  
%<<
%  type status = {
%    mouse_x : int ;
%>>
%   
%                X coordinate of the mouse 
%   
%<<
%    mouse_y : int ;
%>>
%   
%                Y coordinate of the mouse 
%   
%<<
%    button : bool ;
%>>
%   
%                true if a mouse button is pressed 
%   
%<<
%    keypressed : bool ;
%>>
%   
%                true if a key has been pressed 
%   
%<<
%    key : char ;
%>>
%   
%                the character for the key pressed 
%   
%<<
%  }
%>>
%    
%                To report events.
%  
%<<
%  type event =
%    | Button_down
%>>
%   
%                A mouse button is pressed 
%   
%<<
%    | Button_up
%>>
%   
%                A mouse button is released 
%   
%<<
%    | Key_pressed
%>>
%   
%                A key is pressed 
%   
%<<
%    | Mouse_motion
%>>
%   
%                The mouse is moved 
%   
%<<
%    | Poll
%>>
%   
%                Don-t wait; return immediately 
%    
%                To specify events to wait for.
%  
%<<
%  val wait_next_event : event list -> status
%>>
%    
%                Wait until one of the events specified in the given event list 
%               occurs, and return the status of the mouse and keyboard at  that
%               time. If Poll is given in the event list, return immediately 
%               with the current status. If the mouse cursor is outside of the 
%               graphics window, the mouse_x and mouse_y fields of the event are
%                outside the range 0..size_x()-1, 0..size_y()-1. Keypresses  are
%               queued, and dequeued one by one when the Key_pressed  event is
%               specified.
%  
%
%Mouse and keyboard polling
%==========================
%  
%<<
%  val mouse_pos : unit -> int * int
%>>
%    
%                Return the position of the mouse cursor, relative to the 
%               graphics window. If the mouse cursor is outside of the graphics 
%               window, mouse_pos() returns a point outside of the range 
%               0..size_x()-1, 0..size_y()-1.
%  
%<<
%  val button_down : unit -> bool
%>>
%    
%                Return true if the mouse button is pressed, false otherwise.
%  
%<<
%  val read_key : unit -> char
%>>
%    
%                Wait for a key to be pressed, and return the corresponding 
%               character. Keypresses are queued.
%  
%<<
%  val key_pressed : unit -> bool
%>>
%    
%                Return true if a keypress is available; that is, if read_key 
%               would not block.
%  
%
%Sound
%=====
%  
%<<
%  val sound : int -> int -> unit
%>>
%    
%                sound freq dur plays a sound at frequency freq (in hertz)  for
%               a duration dur (in milliseconds).
%  
%
%Double buffering
%================
%  
%<<
%  val auto_synchronize : bool -> unit
%>>
%    
%                By default, drawing takes place both on the window displayed 
%               on screen, and in a memory area (the -'backing store--).  The
%               backing store image is used to re-paint the on-screen  window
%               when necessary.
%               To avoid flicker during animations, it is possible to turn  off
%               on-screen drawing, perform a number of drawing operations  in
%               the backing store only, then refresh the on-screen window 
%               explicitly.
%               auto_synchronize false turns on-screen drawing off. All 
%               subsequent drawing commands are performed on the backing store 
%               only.
%               auto_synchronize true refreshes the on-screen window from  the
%               backing store (as per synchronize), then turns on-screen 
%               drawing back on. All subsequent drawing commands are performed 
%               both on screen and in the backing store.
%               The default drawing mode corresponds to auto_synchronize true.
%  
%<<
%  val synchronize : unit -> unit
%>>
%    
%                Synchronize the backing store and the on-screen window, by 
%               copying the contents of the backing store onto the graphics 
%               window.
%  
%<<
%  val display_mode : bool -> unit
%>>
%    
%                Set display mode on or off. When turned on, drawings are done 
%               in the graphics window; when turned off, drawings do not affect 
%               the graphics window. This occurs independently of  drawing into
%               the backing store (see the function Graphics.remember_mode[25.1]
%                below). Default display mode is on.
%  
%<<
%  val remember_mode : bool -> unit
%>>
%    
%                Set remember mode on or off. When turned on, drawings are done 
%               in the backing store; when turned off, the backing store is 
%               unaffected by drawings. This occurs independently of drawing 
%               onto the graphics window (see the function
%               Graphics.display_mode[25.1] above).  Default remember mode is
%               on.
%  
%    
%  
%
%Chapter 26    The dbm library: access to NDBM databases
%*******************************************************
%   
%  The dbm library provides access to NDBM databases under Unix. NDBM databases
%maintain key/data associations, where both the key and the data are arbitrary
%strings. They support fairly large databases (several gigabytes) and can
%retrieve a keyed item in one or two file system accesses. Refer to the Unix
%manual pages for more information.
%     Unix: 
%                Programs that use the dbm library must be linked as follows: 
%               <<
%                         ocamlc other options dbm.cma other files
%                         ocamlopt other options dbm.cmxa other files
%               >>
%                For interactive use of the dbm library, do: 
%               <<
%                         ocamlmktop -o mytop dbm.cma
%                         ./mytop
%               >>
%                
%   or (if dynamic linking of C libraries is supported on your platform), start
%ocaml and type #load "dbm.cma";;.
%     Windows: 
%                This library is not available. 
%  
%  
%
%26.1  Module Dbm : Interface to the NDBM database.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%<<
%  type t 
%>>
%    
%                The type of file descriptors opened on NDBM databases.
%  
%<<
%  type open_flag =
%    | Dbm_rdonly
%    | Dbm_wronly
%    | Dbm_rdwr
%    | Dbm_create
%>>
%   
%                Flags for opening a database (see Dbm.opendbm[26.1]). 
%   
%<<
%  exception Dbm_error of string
%>>
%    
%                Raised by the following functions when an error is encountered.
%  
%<<
%  val opendbm : string -> open_flag list -> int -> t
%>>
%    
%                Open a descriptor on an NDBM database. The first argument is 
%               the name of the database (without the .dir and .pag suffixes). 
%               The second argument is a list of flags: Dbm_rdonly opens  the
%               database for reading only, Dbm_wronly for writing only, 
%               Dbm_rdwr for reading and writing; Dbm_create causes the 
%               database to be created if it does not already exist.  The third
%               argument is the permissions to give to the database  files, if
%               the database is created.
%  
%<<
%  val close : t -> unit
%>>
%    
%                Close the given descriptor.
%  
%<<
%  val find : t -> string -> string
%>>
%    
%                find db key returns the data associated with the given  key in
%               the database opened for the descriptor db.  Raise Not_found if
%               the key has no associated data.
%  
%<<
%  val add : t -> string -> string -> unit
%>>
%    
%                add db key data inserts the pair (key, data) in  the database
%               db. If the database already contains data  associated with key,
%               raise Dbm_error "Entry already exists".
%  
%<<
%  val replace : t -> string -> string -> unit
%>>
%    
%                replace db key data inserts the pair (key, data) in  the
%               database db. If the database already contains data  associated
%               with key, that data is discarded and silently  replaced by the
%               new data.
%  
%<<
%  val remove : t -> string -> unit
%>>
%    
%                remove db key data removes the data associated with key  in db.
%               If key has no associated data, raise  Dbm_error "dbm_delete".
%  
%<<
%  val firstkey : t -> string
%>>
%    
%                See Dbm.nextkey[26.1].
%  
%<<
%  val nextkey : t -> string
%>>
%    
%                Enumerate all keys in the given database, in an unspecified
%               order.  firstkey db returns the first key, and repeated calls 
%               to nextkey db return the remaining keys. Not_found is raised 
%               when all keys have been enumerated.
%  
%<<
%  val iter : (string -> string -> 'a) -> t -> unit
%>>
%    
%                iter f db applies f to each (key, data) pair in  the database
%               db. f receives key as first argument  and data as second
%               argument.
%  
%   
%   
%  
%
%Chapter 27    The dynlink library: dynamic loading and linking of object files
%******************************************************************************
%   
%  The dynlink library supports type-safe dynamic loading and linking of
%bytecode object files (.cmo and .cma files) in a running bytecode program. Type
%safety is ensured by limiting the set of modules from the running program that
%the loaded object file can access, and checking that the running program and
%the loaded object file have been compiled against the same interfaces for these
%modules.
%  Programs that use the dynlink library simply need to link dynlink.cma with
%their object files and other libraries.  Dynamic linking is available only to
%bytecode programs compiled with ocamlc, not to native'code programs compiled
%with ocamlopt.
%  
%
%27.1  Module Dynlink : Dynamic loading of bytecode object files.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%
%Initialization
%==============
%  
%<<
%  val init : unit -> unit
%>>
%    
%                Initialize the Dynlink library.  Must be called before any
%               other function in this module.
%  
%
%Dynamic loading of compiled bytecode files
%==========================================
%  
%<<
%  val loadfile : string -> unit
%>>
%    
%                Load the given bytecode object file (.cmo file) or  bytecode
%               library file (.cma file), and link it with the running program. 
%               All toplevel expressions in the loaded compilation units  are
%               evaluated. No facilities are provided to  access value names
%               defined by the unit. Therefore, the unit  must register itself
%               its entry points with the main program,  e.g. by modifying
%               tables of functions.
%  
%<<
%  val loadfile_private : string -> unit
%>>
%    
%                Same as loadfile, except that the compilation units just loaded
%                are hidden (cannot be referenced) from other modules
%               dynamically  loaded afterwards.
%  
%
%Access control
%==============
%  
%<<
%  val allow_only : string list -> unit
%>>
%    
%                allow_only units restricts the compilation units that
%               dynamically-linked  units can reference: it only allows
%               references to the units named in  list units. References to any
%               other compilation unit will cause  a Unavailable_unit error
%               during loadfile or loadfile_private.
%               Initially (just after calling init), all compilation units
%               composing  the program currently running are available for
%               reference from  dynamically-linked units. allow_only can be used
%               to grant access  to some of them only, e.g. to the units that
%               compose the API for  dynamically-linked code, and prevent access
%               to all other units,  e.g. private, internal modules of the
%               running program.
%  
%<<
%  val prohibit : string list -> unit
%>>
%    
%                prohibit units prohibits dynamically-linked units from
%               referencing  the units named in list units. This can be used to
%               prevent  access to selected units, e.g. private, internal
%               modules of  the running program.
%  
%<<
%  val default_available_units : unit -> unit
%>>
%    
%                Reset the set of units that can be referenced from
%               dynamically-linked  code to its default value, that is, all
%               units composing the currently  running program.
%  
%<<
%  val allow_unsafe_modules : bool -> unit
%>>
%    
%                Govern whether unsafe object files are allowed to be 
%               dynamically linked. A compilation unit is --unsafe-- if it
%               contains  declarations of external functions, which can break
%               type safety.  By default, dynamic linking of unsafe object files
%               is  not allowed.
%  
%
%Deprecated, low-level API for access control
%============================================
%  
%<<
%  val add_interfaces : string list -> string list -> unit
%>>
%    
%                add_interfaces units path grants dynamically-linked object 
%               files access to the compilation units named in list units.  The
%               interfaces (.cmi files) for these units are searched in  path (a
%               list of directory names).
%  
%<<
%  val add_available_units : (string * Digest.t) list -> unit
%>>
%    
%                Same as Dynlink.add_interfaces[27.1], but instead of searching
%               .cmi files  to find the unit interfaces, uses the interface
%               digests given  for each unit. This way, the .cmi interface files
%               need not be  available at run-time. The digests can be extracted
%               from .cmi  files using the extract_crc program installed in the 
%               Objective Caml standard library directory.
%  
%<<
%  val clear_available_units : unit -> unit
%>>
%    
%                Empty the list of compilation units accessible to
%               dynamically-linked  programs.
%  
%
%Error reporting
%===============
%  
%<<
%  type linking_error =
%    | Undefined_global of string
%    | Unavailable_primitive of string
%    | Uninitialized_global of string
%>>
%   
%<<
%  type error =
%    | Not_a_bytecode_file of string
%    | Inconsistent_import of string
%    | Unavailable_unit of string
%    | Unsafe_file
%    | Linking_error of string * linking_error
%    | Corrupted_interface of string
%    | File_not_found of string
%    | Cannot_open_dll of string
%>>
%   
%<<
%  exception Error of error
%>>
%    
%                Errors in dynamic linking are reported by raising the Error 
%               exception with a description of the error.
%  
%<<
%  val error_message : error -> string
%>>
%    
%                Convert an error description to a printable message.
%  
%   
%   
%  
%
%Chapter 28    The LablTk library: Tcl/Tk GUI interface
%******************************************************
%   
%  The labltk library provides access to the Tcl/Tk GUI from Objective Caml
%programs. This interface is generated in an automated way, and you should refer
%to Tcl/Tk books and man pages for detailed information on the behavior of the
%numerous functions. We also suggest to use ocamlbrowser to see the types of the
%various functions, that are the best documentation for the library itself. 
%  
%  Programs that use the labltk library must be linked as follows: 
%<<
%          ocamlc other options -I +labltk labltk.cma other files
%          ocamlopt other options -I +labltk labltk.cmxa other files
%>>
%  
%     Unix: 
%                The labltk library is available for any system with Tcl/Tk
%               installed, starting from Tcl 7.5/Tk 4.1 up to Tcl/Tk 8.3. Beware
%               that some beta versions may have compatibility problems.
%               If the library was not compiled correctly, try to run again the
%               configure script with the option -tkdefs switches, where
%               switches is a list of C-style inclusion paths leading to the
%               right tcl.h and tk.h, for instance --I/usr/local/include/tcl8.3
%               -I/usr/local/include/tk8.3-.
%               A script is installed, to make easier the use of the labltk
%               library as toplevel. 
%                 
%                labltk  This is a toplevel including the labltk library, and
%                  the path is already set as to allow the use of the various
%                  modules. It also includes code for the Unix and Str
%                  libraries. You can use it in place of ocaml. 
%                
%  
%     Windows: 
%                The labltk library has been precompiled for use with Tcl/Tk
%               8.3. You must first have it installed on your system. It can be
%               downloaded from
%               http://www.scriptics.com/products/tcltk/8.3.html. After
%               installing it, you must put the dynamically loaded libraries
%               tcl83.dll and tk83.dll (from the bin directory of the Tcl
%               installation) in a directory included in you path.
%               No toplevel is available, but you can load the library from the
%               standard toplevel with the following commands. 
%                            
%                           <<
%                             # #directory "+labltk";;
%                             # #load "labltk.cma";;
%                           >>
%                You can also load it directly from the command line. 
%                            
%                           <<
%                             C:\ocaml\bin> ocaml -I +labltk labltk.cma
%                           >>
%                
%  
%  The labltk library is composed of a large number of modules. 
%                
%               <<
%                 Bell                Imagebitmap         Place
%                 Button              Imagephoto          Radiobutton
%                 Canvas              Label               Scale
%                 Checkbutton         Listbox             Scrollbar
%                 Clipboard           Menu                Selection
%                 Dialog              Menubutton          Text
%                 Entry               Message             Tk
%                 Focus               Option              Tkwait
%                 Frame               Optionmenu          Toplevel
%                 Grab                Pack                Winfo
%                 Grid                Palette             Wm
%               >>
%  
%  Giving a detailed account of each of these module would be impractical here.
%We will just present some of the basic functions in the module Tk. Note that
%for most other modules information can be found in the Tcl man page of their
%name.
%  
%
%28.1  Module Tk : Basic functions and types for LablTk
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%   
%  0.5cm
%
%Initialization and termination
%==============================
%  
%<<
%  val openTk :
%    ?display:string -> ?clas:string -> unit -> Widget.toplevel Widget.widget
%>>
%    
%                Initialize LablTk and open a toplevel window.  display is
%               described according to the X11 conventions.  clas is used for
%               the X11 resource mechanism.
%  
%<<
%  val mainLoop : unit -> unit
%>>
%    
%                Start the main event loop
%  
%<<
%  val closeTk : unit -> unit
%>>
%    
%                Quit the main loop and close all open windows.
%  
%<<
%  val destroy : 'a Widget.widget -> unit
%>>
%    
%                Destroy an individual widget.
%  
%
%Application wide commands
%=========================
%  
%<<
%  val update : unit -> unit
%>>
%    
%                Synchronize display with internal state.
%  
%<<
%  val appname_get : unit -> string
%>>
%   
%<<
%  val appname_set : string -> unit
%>>
%    
%                Get or set the application name.
%  
%
%Dimensions
%==========
%  
%<<
%  type units = [ 'cm of float | -In of float | -Mm of float | -Pix of int | -Pt
%of float ] 
%>>
%   
%<<
%  val pixels : units -> int
%>>
%    
%                Converts various on-screen units to pixels,  respective to the
%               default display. Available units are  pixels, centimeters,
%               inches, millimeters and points
%  
%
%Widget layout commands
%======================
%  
%<<
%  type anchor = [ 'center | -E | -N | -Ne | -Nw | -S | -Se | -Sw | -W ] 
%>>
%   
%<<
%  type fillMode = [ 'both | -None | -X | -Y ] 
%>>
%   
%<<
%  type side = [ 'bottom | -Left | -Right | -Top ] 
%>>
%   
%<<
%  val pack :
%    ?after:'a Widget.widget ->
%    ?anchor:anchor ->
%    ?before:'b Widget.widget ->
%    ?expand:bool ->
%    ?fill:fillMode ->
%    ?inside:'c Widget.widget ->
%    ?ipadx:int ->
%    ?ipady:int ->
%    ?padx:int -> ?pady:int -> ?side:side -> 'd Widget.widget list -> unit
%>>
%    
%                Pack a widget inside its parent,  using the standard layout
%               engine.
%  
%<<
%  val grid :
%    ?column:int ->
%    ?columnspan:int ->
%    ?inside:'a Widget.widget ->
%    ?ipadx:int ->
%    ?ipady:int ->
%    ?padx:int ->
%    ?pady:int ->
%    ?row:int -> ?rowspan:int -> ?sticky:string -> 'b Widget.widget list -> unit
%>>
%    
%                Pack a widget inside its parent, using the grid layout engine.
%  
%<<
%  type borderMode = [ -Ignore | -Inside | -Outside ] 
%>>
%   
%<<
%  val place :
%    ?anchor:anchor ->
%    ?bordermode:borderMode ->
%    ?height:int ->
%    ?inside:'a Widget.widget ->
%    ?relheight:float ->
%    ?relwidth:float ->
%    ?relx:float ->
%    ?rely:float -> ?width:int -> ?x:int -> ?y:int -> 'b Widget.widget -> unit
%>>
%    
%                Pack a widget inside its parent, at absolute coordinates.
%  
%<<
%  val raise_window : ?above:'a Widget.widget -> 'b Widget.widget -> unit
%>>
%   
%<<
%  val lower_window : ?below:'a Widget.widget -> 'b Widget.widget -> unit
%>>
%    
%                Raise or lower the window associated to a widget.
%  
%
%Event handling
%==============
%  
%<<
%  type modifier = [ 'alt
%    | 'button1
%    | 'button2
%    | 'button3
%    | 'button4
%    | 'button5
%    | 'control
%    | 'double
%    | -Lock
%    | -Meta
%    | -Mod1
%    | -Mod2
%    | -Mod3
%    | -Mod4
%    | -Mod5
%    | -Shift
%    | -Triple ] 
%>>
%   
%<<
%  type event = [ 'buttonPress
%    | 'buttonPressDetail of int
%    | 'buttonRelease
%    | 'buttonReleaseDetail of int
%    | 'circulate
%    | 'colorMap
%    | 'configure
%    | 'destroy
%    | -Enter
%    | -Expose
%    | -FocusIn
%    | -FocusOut
%    | -Gravity
%    | -KeyPress
%    | -KeyPressDetail of string
%    | -KeyRelease
%    | -KeyReleaseDetail of string
%    | -Leave
%    | -Map
%    | -Modified of modifier list * event
%    | -Motion
%    | -Property
%    | -Reparent
%    | -Unmap
%    | -Visibility ] 
%>>
%   
%  An event can be either a basic X event, or modified by a  key or mouse
%modifier.
%<<
%  type eventInfo = {
%    mutable ev_Above : int ;
%    mutable ev_ButtonNumber : int ;
%    mutable ev_Count : int ;
%    mutable ev_Detail : string ;
%    mutable ev_Focus : bool ;
%    mutable ev_Height : int ;
%    mutable ev_KeyCode : int ;
%    mutable ev_Mode : string ;
%    mutable ev_OverrideRedirect : bool ;
%    mutable ev_Place : string ;
%    mutable ev_State : string ;
%    mutable ev_Time : int ;
%    mutable ev_Width : int ;
%    mutable ev_MouseX : int ;
%    mutable ev_MouseY : int ;
%    mutable ev_Char : string ;
%    mutable ev_BorderWidth : int ;
%    mutable ev_SendEvent : bool ;
%    mutable ev_KeySymString : string ;
%    mutable ev_KeySymInt : int ;
%    mutable ev_RootWindow : int ;
%    mutable ev_SubWindow : int ;
%    mutable ev_Type : int ;
%    mutable ev_Widget : Widget.any Widget.widget ;
%    mutable ev_RootX : int ;
%    mutable ev_RootY : int ;
%  }
%>>
%   
%  Event related information accessible in callbacks.
%<<
%  type eventField = [ -above
%    | -borderWidth
%    | -buttonNumber
%    | -char
%    | -count
%    | -detail
%    | -Focus
%    | -Height
%    | -KeyCode
%    | -KeySymInt
%    | -KeySymString
%    | -Mode
%    | -MouseX
%    | -MouseY
%    | -OverrideRedirect
%    | -Place
%    | -RootWindow
%    | -RootX
%    | -RootY
%    | -SendEvent
%    | -State
%    | -SubWindow
%    | -Time
%    | -Type
%    | -Widget
%    | -Width ] 
%>>
%   
%  In order to access the above event information, one has to pass  a list of
%required event fields to the bind function.
%<<
%  val bind :
%    events:event list ->
%    ?extend:bool ->
%    ?breakable:bool ->
%    ?fields:eventField list ->
%    ?action:(eventInfo -> unit) -> 'a Widget.widget -> unit
%>>
%    
%                Bind a succession of events on a widget to an action.  If
%               extend is true then then binding is added after existing  ones,
%               otherwise it replaces them.  breakable should be true when break
%               is to be called inside  the action.  action is called with the
%               fields required set in  an eventInfo structure. Other fields
%               should not be accessed.  If action is omitted then existing
%               bindings are removed.
%  
%<<
%  val bind_class :
%    events:event list ->
%    ?extend:bool ->
%    ?breakable:bool ->
%    ?fields:eventField list ->
%    ?action:(eventInfo -> unit) -> ?on:'a Widget.widget -> string -> unit
%>>
%    
%                Same thing for all widgets of a given class. If a widget  is
%               given with label ~on:, the binding will be removed as  soon as
%               it is destroyed.
%  
%<<
%  val bind_tag :
%    events:event list ->
%    ?extend:bool ->
%    ?breakable:bool ->
%    ?fields:eventField list ->
%    ?action:(eventInfo -> unit) -> ?on:'a Widget.widget -> string -> unit
%>>
%    
%                Same thing for all widgets having a given tag
%  
%<<
%  val break : unit -> unit
%>>
%    
%                Used inside a bound action, do not call other actions  after
%               this one. This is only possible if this action  was bound with
%               ~breakable:true.
%  
%   
%   
%  
%
%Chapter 29    The bigarray library
%**********************************
%   
%  The bigarray library implements large, multi-dimensional, numerical arrays.
%These arrays are called -'big arrays-- to distinguish them from the standard
%Caml arrays described in  section 20.2. The main differences between -'big
%arrays-- and standard Caml arrays are as follows: 
%  
% - Big arrays are not limited in size, unlike Caml arrays (float array are
%   limited to 2097151 elements on a 32'bit platform, other array types to
%   4194303 elements). 
% - Big arrays are multi-dimensional. Any number of dimensions between 1 and 16
%   is supported. In contrast, Caml arrays are mono-dimensional and require
%   encoding multi-dimensional arrays as arrays of arrays. 
% - Big arrays can only contain integers and floating-point numbers, while Caml
%   arrays can contain arbitrary Caml data types. However, big arrays provide
%   more space-efficient storage of integer and floating-point elements, in
%   particular because they support --small-- types such as single-precision
%   floats and 8 and 16'bit integers, in addition to the standard Caml types of
%   double-precision floats and 32 and 64'bit integers. 
% - The memory layout of big arrays is entirely compatible with that of arrays
%   in C and Fortran, allowing large arrays to be passed back and forth between
%   Caml code and C / Fortran code with no data copying at all. 
% - Big arrays support interesting high-level operations that normal arrays do
%   not provide efficiently, such as extracting sub'arrays and --slicing-- a
%   multi-dimensional array along certain dimensions, all without any copying. 
%   Programs that use the bigarray library must be linked as follows: 
%<<
%          ocamlc other options bigarray.cma other files
%          ocamlopt other options bigarray.cmxa other files
%>>
%   For interactive use of the bigarray library, do: 
%<<
%          ocamlmktop -o mytop bigarray.cma
%          ./mytop
%>>
%   or (if dynamic linking of C libraries is supported on your platform), start
%ocaml and type #load "bigarray.cma";;.
%  
%
%29.1  Module Bigarray : Large, multi-dimensional, numerical arrays.
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
%
%   
%  This module implements multi-dimensional arrays of integers and 
%floating-point numbers, thereafter referred to as -'big arrays--.  The
%implementation allows efficient sharing of large numerical  arrays between Caml
%code and C or Fortran numerical libraries.
%  Concerning the naming conventions, users of this module are encouraged  to do
%open Bigarray in their source, then refer to array types and  operations via
%short dot notation, e.g. Array1.t or Array2.sub.
%  Big arrays support all the Caml ad-hoc polymorphic operations:
%  
% - comparisons (=, <>, <=, etc, as well as Pervasives.compare[19.2]); 
% - hashing (module Hash); 
% - and structured input-output (Pervasives.output_value[19.2]   and
%   Pervasives.input_value[19.2], as well as the functions from the  
%   Marshal[20.19] module). 
%  
%  0.5cm
%
%Element kinds
%=============
%  
%  Big arrays can contain elements of the following kinds:
%  
% - IEEE single precision (32 bits) floating-point numbers 
%   (Bigarray.float32_elt[29.1]), 
% - IEEE double precision (64 bits) floating-point numbers 
%   (Bigarray.float64_elt[29.1]), 
% - IEEE single precision (2 * 32 bits) floating-point complex numbers 
%   (Bigarray.complex32_elt[29.1]), 
% - IEEE double precision (2 * 64 bits) floating-point complex numbers 
%   (Bigarray.complex64_elt[29.1]), 
% - 8'bit integers (signed or unsigned)  (Bigarray.int8_signed_elt[29.1] or
%   Bigarray.int8_unsigned_elt[29.1]), 
% - 16'bit integers (signed or unsigned)  (Bigarray.int16_signed_elt[29.1] or
%   Bigarray.int16_unsigned_elt[29.1]), 
% - Caml integers (signed, 31 bits on 32'bit architectures,   63 bits on 64'bit
%   architectures) (Bigarray.int_elt[29.1]), 
% - 32'bit signed integer (Bigarray.int32_elt[29.1]), 
% - 64'bit signed integers (Bigarray.int64_elt[29.1]), 
% - platform-native signed integers (32 bits on 32'bit architectures,  64 bits
%   on 64'bit architectures) (Bigarray.nativeint_elt[29.1]). 
%  
%  Each element kind is represented at the type level by one  of the abstract
%types defined below.
%<<
%  type float32_elt 
%>>
%   
%<<
%  type float64_elt 
%>>
%   
%<<
%  type complex32_elt 
%>>
%   
%<<
%  type complex64_elt 
%>>
%   
%<<
%  type int8_signed_elt 
%>>
%   
%<<
%  type int8_unsigned_elt 
%>>
%   
%<<
%  type int16_signed_elt 
%>>
%   
%<<
%  type int16_unsigned_elt 
%>>
%   
%<<
%  type int_elt 
%>>
%   
%<<
%  type int32_elt 
%>>
%   
%<<
%  type int64_elt 
%>>
%   
%<<
%  type nativeint_elt 
%>>
%   
%<<
%  type ('a, 'b) kind 
%>>
%    
%                To each element kind is associated a Caml type, which is  the
%               type of Caml values that can be stored in the big array  or read
%               back from it. This type is not necessarily the same  as the type
%               of the array elements proper: for instance,   a big array whose
%               elements are of kind float32_elt contains  32'bit single
%               precision floats, but reading or writing one of  its elements
%               from Caml uses the Caml type float, which is  64'bit double
%               precision floats.
%               The abstract type ('a, 'b) kind captures this association  of a
%               Caml type 'a for values read or written in the big array,  and
%               of an element kind 'b which represents the actual contents  of
%               the big array. The following predefined values of type  kind
%               list all possible associations of Caml types with  element
%               kinds:
%  
%<<
%  val float32 : (float, float32_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val float64 : (float, float64_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val complex32 : (Complex.t, complex32_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val complex64 : (Complex.t, complex64_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val int8_signed : (int, int8_signed_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val int8_unsigned : (int, int8_unsigned_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val int16_signed : (int, int16_signed_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val int16_unsigned : (int, int16_unsigned_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val int : (int, int_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val int32 : (int32, int32_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val int64 : (int64, int64_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val nativeint : (nativeint, nativeint_elt) kind
%>>
%    
%                See Bigarray.char[29.1].
%  
%<<
%  val char : (char, int8_unsigned_elt) kind
%>>
%    
%                As shown by the types of the values above,  big arrays of kind
%               float32_elt and float64_elt are  accessed using the Caml type
%               float. Big arrays of complex kinds  complex32_elt, complex64_elt
%               are accessed with the Caml type  Complex.t[20.6]. Big arrays of 
%               integer kinds are accessed using the smallest Caml integer  type
%               large enough to represent the array elements:  int for 8- and
%               16'bit integer bigarrays, as well as Caml-integer  bigarrays;
%               int32 for 32'bit integer bigarrays; int64  for 64'bit integer
%               bigarrays; and nativeint for  platform-native integer bigarrays.
%               Finally, big arrays of  kind int8_unsigned_elt can also be
%               accessed as arrays of  characters instead of arrays of small
%               integers, by using  the kind value char instead of
%               int8_unsigned.
%  
%
%Array layouts
%=============
%  
%<<
%  type c_layout 
%>>
%    
%                See Bigarray.fortran_layout[29.1].
%  
%<<
%  type fortran_layout 
%>>
%    
%                To facilitate interoperability with existing C and Fortran
%               code,  this library supports two different memory layouts for
%               big arrays,  one compatible with the C conventions,  the other
%               compatible with the Fortran conventions.
%               In the C-style layout, array indices start at 0, and  
%               multi-dimensional arrays are laid out in row-major format.  That
%               is, for a two-dimensional array, all elements of  row 0 are
%               contiguous in memory, followed by all elements of  row 1, etc.
%               In other terms, the array elements at (x,y)  and (x, y+1) are
%               adjacent in memory.
%               In the Fortran-style layout, array indices start at 1, and  
%               multi-dimensional arrays are laid out in column-major format. 
%               That is, for a two-dimensional array, all elements of  column 0
%               are contiguous in memory, followed by all elements of  column 1,
%               etc. In other terms, the array elements at (x,y)  and (x+1, y)
%               are adjacent in memory.
%               Each layout style is identified at the type level by the 
%               abstract types Bigarray.c_layout[29.1] and fortran_layout
%               respectively.
%  
%<<
%  type 'a layout 
%>>
%    
%                The type 'a layout represents one of the two supported  memory
%               layouts: C-style if 'a is Bigarray.c_layout[29.1], Fortran-style
%                if 'a is Bigarray.fortran_layout[29.1].
%  
%
%Supported layouts
%-----------------
%  
%  The abstract values c_layout and fortran_layout represent  the two supported
%layouts at the level of values.
%<<
%  val c_layout : c_layout layout
%>>
%   
%<<
%  val fortran_layout : fortran_layout layout
%>>
%
%
%Generic arrays (of arbitrarily many dimensions)
%===============================================
%  
%<<
%  module Genarray : >>
%   
%    sig
% 
%  
%   <<
%     type ('a, 'b, 'c) t 
%   >>
%   
%                   The type Genarray.t is the type of big arrays with variable 
%                  numbers of dimensions. Any number of dimensions between 1 and
%                  16  is supported.
%                  The three type parameters to Genarray.t identify the array
%                  element  kind and layout, as follows:
%                    
%                   - the first parameter, 'a, is the Caml type for accessing
%                     array  elements (float, int, int32, int64, nativeint); 
%                   - the second parameter, 'b, is the actual kind of array
%                     elements  (float32_elt, float64_elt, int8_signed_elt,
%                     int8_unsigned_elt,  etc); 
%                   - the third parameter, 'c, identifies the array layout 
%                     (c_layout or fortran_layout). 
%                  
%                  For instance, (float, float32_elt, fortran_layout) Genarray.t
%                   is the type of generic big arrays containing 32'bit floats 
%                  in Fortran layout; reads and writes in this array use the 
%                  Caml type float.
% 
%   <<
%     val create :
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> int array -> ('a, 'b, 'c) t
%   >>
%   
%                   Genarray.create kind layout dimensions returns a new big
%                  array  whose element kind is determined by the parameter kind
%                  (one of  float32, float64, int8_signed, etc) and whose layout
%                  is  determined by the parameter layout (one of c_layout or 
%                  fortran_layout). The dimensions parameter is an array of 
%                  integers that indicate the size of the big array in each
%                  dimension.  The length of dimensions determines the number of
%                  dimensions  of the bigarray.
%                  For instance, Genarray.create int32 c_layout [|4;6;8|] 
%                  returns a fresh big array of 32'bit integers, in C layout, 
%                  having three dimensions, the three dimensions being 4, 6 and
%                  8  respectively.
%                  Big arrays returned by Genarray.create are not initialized: 
%                  the initial values of array elements is unspecified.
%                  Genarray.create raises Invalid_arg if the number of
%                  dimensions  is not in the range 1 to 16 inclusive, or if one
%                  of the dimensions  is negative.
% 
%   <<
%     val num_dims : ('a, 'b, 'c) t -> int
%   >>
%   
%                   Return the number of dimensions of the given big array.
% 
%   <<
%     val dims : ('a, 'b, 'c) t -> int array
%   >>
%   
%                   Genarray.dims a returns all dimensions of the big array a, 
%                  as an array of integers of length Genarray.num_dims a.
% 
%   <<
%     val nth_dim : ('a, 'b, 'c) t -> int -> int
%   >>
%   
%                   Genarray.nth_dim a n returns the n-th dimension of the  big
%                  array a. The first dimension corresponds to n = 0;  the
%                  second dimension corresponds to n = 1; the last dimension, 
%                  to n = Genarray.num_dims a - 1.  Raise Invalid_arg if n is
%                  less than 0 or greater or equal than  Genarray.num_dims a.
% 
%   <<
%     val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
%   >>
%   
%                   Return the kind of the given big array.
% 
%   <<
%     val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
%   >>
%   
%                   Return the layout of the given big array.
% 
%   <<
%     val get : ('a, 'b, 'c) t -> int array -> 'a
%   >>
%   
%                   Read an element of a generic big array.  Genarray.get a
%                  [|i1; ...; iN|] returns the element of a  whose coordinates
%                  are i1 in the first dimension, i2 in  the second dimension,
%                  ..., iN in the N-th dimension.
%                  If a has C layout, the coordinates must be greater or equal
%                  than 0  and strictly less than the corresponding dimensions
%                  of a.  If a has Fortran layout, the coordinates must be
%                  greater or equal  than 1 and less or equal than the
%                  corresponding dimensions of a.  Raise Invalid_arg if the
%                  array a does not have exactly N  dimensions, or if the
%                  coordinates are outside the array bounds.
%                  If N > 3, alternate syntax is provided: you can write  a.{i1,
%                  i2, ..., iN} instead of Genarray.get a [|i1; ...; iN|].  (The
%                  syntax a.{...} with one, two or three coordinates is 
%                  reserved for accessing one-, two- and three-dimensional
%                  arrays  as described below.)
% 
%   <<
%     val set : ('a, 'b, 'c) t -> int array -> 'a -> unit
%   >>
%   
%                   Assign an element of a generic big array.  Genarray.set a
%                  [|i1; ...; iN|] v stores the value v in the  element of a
%                  whose coordinates are i1 in the first dimension,  i2 in the
%                  second dimension, ..., iN in the N-th dimension.
%                  The array a must have exactly N dimensions, and all
%                  coordinates  must lie inside the array bounds, as described
%                  for Genarray.get;  otherwise, Invalid_arg is raised.
%                  If N > 3, alternate syntax is provided: you can write  a.{i1,
%                  i2, ..., iN} <- v instead of  Genarray.set a [|i1; ...; iN|]
%                  v.  (The syntax a.{...} <- v with one, two or three
%                  coordinates is  reserved for updating one-, two- and
%                  three-dimensional arrays  as described below.)
% 
%   <<
%     val sub_left :
%       ('a, 'b, Bigarray.c_layout) t ->
%       int -> int -> ('a, 'b, Bigarray.c_layout) t
%   >>
%   
%                   Extract a sub'array of the given big array by restricting
%                  the  first (left-most) dimension. Genarray.sub_left a ofs len
%                   returns a big array with the same number of dimensions as a,
%                   and the same dimensions as a, except the first dimension, 
%                  which corresponds to the interval [ofs ... ofs + len - 1]  of
%                  the first dimension of a. No copying of elements is 
%                  involved: the sub'array and the original array share the same
%                   storage space. In other terms, the element at coordinates 
%                  [|i1; ...; iN|] of the sub'array is identical to the  element
%                  at coordinates [|i1+ofs; ...; iN|] of the original  array a.
%                  Genarray.sub_left applies only to big arrays in C layout. 
%                  Raise Invalid_arg if ofs and len do not designate  a valid
%                  sub'array of a, that is, if ofs < 0, or len < 0,  or ofs +
%                  len > Genarray.nth_dim a 0.
% 
%   <<
%     val sub_right :
%       ('a, 'b, Bigarray.fortran_layout) t ->
%       int -> int -> ('a, 'b, Bigarray.fortran_layout) t
%   >>
%   
%                   Extract a sub'array of the given big array by restricting
%                  the  last (right-most) dimension. Genarray.sub_right a ofs
%                  len  returns a big array with the same number of dimensions
%                  as a,  and the same dimensions as a, except the last
%                  dimension,  which corresponds to the interval [ofs ... ofs +
%                  len - 1]  of the last dimension of a. No copying of elements
%                  is  involved: the sub'array and the original array share the
%                  same  storage space. In other terms, the element at
%                  coordinates  [|i1; ...; iN|] of the sub'array is identical to
%                  the  element at coordinates [|i1; ...; iN+ofs|] of the
%                  original  array a.
%                  Genarray.sub_right applies only to big arrays in Fortran
%                  layout.  Raise Invalid_arg if ofs and len do not designate  a
%                  valid sub'array of a, that is, if ofs < 1, or len < 0,  or
%                  ofs + len > Genarray.nth_dim a (Genarray.num_dims a - 1).
% 
%   <<
%     val slice_left :
%       ('a, 'b, Bigarray.c_layout) t ->
%       int array -> ('a, 'b, Bigarray.c_layout) t
%   >>
%   
%                   Extract a sub'array of lower dimension from the given big
%                  array  by fixing one or several of the first (left-most)
%                  coordinates.  Genarray.slice_left a [|i1; ... ; iM|] returns
%                  the --slice--  of a obtained by setting the first M
%                  coordinates to  i1, ..., iM. If a has N dimensions, the slice
%                  has  dimension N - M, and the element at coordinates  [|j1;
%                  ...; j(N-M)|] in the slice is identical to the element  at
%                  coordinates [|i1; ...; iM; j1; ...; j(N-M)|] in the original 
%                  array a. No copying of elements is involved: the slice and 
%                  the original array share the same storage space.
%                  Genarray.slice_left applies only to big arrays in C layout. 
%                  Raise Invalid_arg if M >= N, or if [|i1; ... ; iM|]  is
%                  outside the bounds of a.
% 
%   <<
%     val slice_right :
%       ('a, 'b, Bigarray.fortran_layout) t ->
%       int array -> ('a, 'b, Bigarray.fortran_layout) t
%   >>
%   
%                   Extract a sub'array of lower dimension from the given big
%                  array  by fixing one or several of the last (right-most)
%                  coordinates.  Genarray.slice_right a [|i1; ... ; iM|] returns
%                  the --slice--  of a obtained by setting the last M
%                  coordinates to  i1, ..., iM. If a has N dimensions, the slice
%                  has  dimension N - M, and the element at coordinates  [|j1;
%                  ...; j(N-M)|] in the slice is identical to the element  at
%                  coordinates [|j1; ...; j(N-M); i1; ...; iM|] in the original 
%                  array a. No copying of elements is involved: the slice and 
%                  the original array share the same storage space.
%                  Genarray.slice_right applies only to big arrays in Fortran
%                  layout.  Raise Invalid_arg if M >= N, or if [|i1; ... ; iM|] 
%                  is outside the bounds of a.
% 
%   <<
%     val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
%   >>
%   
%                   Copy all elements of a big array in another big array. 
%                  Genarray.blit src dst copies all elements of src into  dst.
%                  Both arrays src and dst must have the same number of 
%                  dimensions and equal dimensions. Copying a sub'array of src 
%                  to a sub'array of dst can be achieved by applying
%                  Genarray.blit  to sub'array or slices of src and dst.
% 
%   <<
%     val fill : ('a, 'b, 'c) t -> 'a -> unit
%   >>
%   
%                   Set all elements of a big array to a given value. 
%                  Genarray.fill a v stores the value v in all elements of  the
%                  big array a. Setting only some elements of a to v  can be
%                  achieved by applying Genarray.fill to a sub'array  or a slice
%                  of a.
% 
%   <<
%     val map_file :
%       Unix.file_descr ->
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> bool -> int array -> ('a, 'b, 'c) t
%   >>
%   
%                   Memory mapping of a file as a big array.  Genarray.map_file
%                  fd kind layout shared dims  returns a big array of kind kind,
%                  layout layout,  and dimensions as specified in dims. The data
%                  contained in  this big array are the contents of the file
%                  referred to by  the file descriptor fd (as opened previously
%                  with  Unix.openfile, for example). If shared is true,  all
%                  modifications performed on the array are reflected in  the
%                  file. This requires that fd be opened with write permissions.
%                   If shared is false, modifications performed on the array 
%                  are done in memory only, using copy-on-write of the modified 
%                  pages; the underlying file is not affected.
%                  Genarray.map_file is much more efficient than reading  the
%                  whole file in a big array, modifying that big array,  and
%                  writing it afterwards.
%                  To adjust automatically the dimensions of the big array to 
%                  the actual size of the file, the major dimension (that is, 
%                  the first dimension for an array with C layout, and the last 
%                  dimension for an array with Fortran layout) can be given as 
%                  -1. Genarray.map_file then determines the major dimension 
%                  from the size of the file. The file must contain an integral 
%                  number of sub'arrays as determined by the non-major
%                  dimensions,  otherwise Failure is raised.
%                  If all dimensions of the big array are given, the file size
%                  is  matched against the size of the big array. If the file is
%                  larger  than the big array, only the initial portion of the
%                  file is  mapped to the big array. If the file is smaller than
%                  the big  array, the file is automatically grown to the size
%                  of the big array.  This requires write permissions on fd.
% 
%  
%  -  end
%  
%
%One-dimensional arrays
%======================
%  
%<<
%  module Array1 : >>
%   
%    sig
% 
%  
%   <<
%     type ('a, 'b, 'c) t 
%   >>
%   
%                   The type of one-dimensional big arrays whose elements have 
%                  Caml type 'a, representation kind 'b, and memory layout 'c.
% 
%   <<
%     val create :
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> int -> ('a, 'b, 'c) t
%   >>
%   
%                   Array1.create kind layout dim returns a new bigarray of  one
%                  dimension, whose size is dim. kind and layout  determine the
%                  array element kind and the array layout  as described for
%                  Genarray.create.
% 
%   <<
%     val dim : ('a, 'b, 'c) t -> int
%   >>
%   
%                   Return the size (dimension) of the given one-dimensional  
%                  big array.
% 
%   <<
%     val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
%   >>
%   
%                   Return the kind of the given big array.
% 
%   <<
%     val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
%   >>
%   
%                   Return the layout of the given big array.
% 
%   <<
%     val get : ('a, 'b, 'c) t -> int -> 'a
%   >>
%   
%                   Array1.get a x, or alternatively a.{x},   returns the
%                  element of a at index x.  x must be greater or equal than 0
%                  and strictly less than  Array1.dim a if a has C layout. If a
%                  has Fortran layout,  x must be greater or equal than 1 and
%                  less or equal than  Array1.dim a. Otherwise, Invalid_arg is
%                  raised.
% 
%   <<
%     val set : ('a, 'b, 'c) t -> int -> 'a -> unit
%   >>
%   
%                   Array1.set a x v, also written a.{x} <- v,  stores the value
%                  v at index x in a.  x must be inside the bounds of a as
%                  described in   Bigarray.Array1.get[29.1];  otherwise,
%                  Invalid_arg is raised.
% 
%   <<
%     val sub : ('a, 'b, 'c) t ->
%       int -> int -> ('a, 'b, 'c) t
%   >>
%   
%                   Extract a sub'array of the given one-dimensional big array. 
%                  See Genarray.sub_left for more details.
% 
%   <<
%     val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
%   >>
%   
%                   Copy the first big array to the second big array.  See
%                  Genarray.blit for more details.
% 
%   <<
%     val fill : ('a, 'b, 'c) t -> 'a -> unit
%   >>
%   
%                   Fill the given big array with the given value.  See
%                  Genarray.fill for more details.
% 
%   <<
%     val of_array :
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> 'a array -> ('a, 'b, 'c) t
%   >>
%   
%                   Build a one-dimensional big array initialized from the 
%                  given array.
% 
%   <<
%     val map_file :
%       Unix.file_descr ->
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> bool -> int -> ('a, 'b, 'c) t
%   >>
%   
%                   Memory mapping of a file as a one-dimensional big array. 
%                  See Bigarray.Genarray.map_file[29.1] for more details.
% 
%  
%  -  end
%  
%                One-dimensional arrays. The Array1 structure provides
%               operations  similar to those of  Bigarray.Genarray[29.1], but
%               specialized to the case of one-dimensional arrays.  (The Array2
%               and Array3 structures below provide operations  specialized for
%               two- and three-dimensional arrays.)  Statically knowing the
%               number of dimensions of the array allows  faster operations, and
%               more precise static type'checking.
%  
%
%Two-dimensional arrays
%======================
%  
%<<
%  module Array2 : >>
%   
%    sig
% 
%  
%   <<
%     type ('a, 'b, 'c) t 
%   >>
%   
%                   The type of two-dimensional big arrays whose elements have 
%                  Caml type 'a, representation kind 'b, and memory layout 'c.
% 
%   <<
%     val create :
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> int -> int -> ('a, 'b, 'c) t
%   >>
%   
%                   Array2.create kind layout dim1 dim2 returns a new bigarray
%                  of  two dimension, whose size is dim1 in the first dimension 
%                  and dim2 in the second dimension. kind and layout  determine
%                  the array element kind and the array layout  as described for
%                  Bigarray.Genarray.create[29.1].
% 
%   <<
%     val dim1 : ('a, 'b, 'c) t -> int
%   >>
%   
%                   Return the first dimension of the given two-dimensional big
%                  array.
% 
%   <<
%     val dim2 : ('a, 'b, 'c) t -> int
%   >>
%   
%                   Return the second dimension of the given two-dimensional big
%                  array.
% 
%   <<
%     val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
%   >>
%   
%                   Return the kind of the given big array.
% 
%   <<
%     val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
%   >>
%   
%                   Return the layout of the given big array.
% 
%   <<
%     val get : ('a, 'b, 'c) t -> int -> int -> 'a
%   >>
%   
%                   Array2.get a x y, also written a.{x,y},  returns the element
%                  of a at coordinates (x, y).  x and y must be within the
%                  bounds  of a, as described for Bigarray.Genarray.get[29.1];  
%                  otherwise, Invalid_arg is raised.
% 
%   <<
%     val set : ('a, 'b, 'c) t -> int -> int -> 'a -> unit
%   >>
%   
%                   Array2.set a x y v, or alternatively a.{x,y} <- v,  stores
%                  the value v at coordinates (x, y) in a.  x and y must be
%                  within the bounds of a,  as described for
%                  Bigarray.Genarray.set[29.1];  otherwise, Invalid_arg is
%                  raised.
% 
%   <<
%     val sub_left :
%       ('a, 'b, Bigarray.c_layout) t ->
%       int -> int -> ('a, 'b, Bigarray.c_layout) t
%   >>
%   
%                   Extract a two-dimensional sub'array of the given
%                  two-dimensional   big array by restricting the first
%                  dimension.  See Bigarray.Genarray.sub_left[29.1] for more
%                  details.   Array2.sub_left applies only to arrays with C
%                  layout.
% 
%   <<
%     val sub_right :
%       ('a, 'b, Bigarray.fortran_layout) t ->
%       int -> int -> ('a, 'b, Bigarray.fortran_layout) t
%   >>
%   
%                   Extract a two-dimensional sub'array of the given
%                  two-dimensional   big array by restricting the second
%                  dimension.  See Bigarray.Genarray.sub_right[29.1] for more
%                  details.   Array2.sub_right applies only to arrays with
%                  Fortran layout.
% 
%   <<
%     val slice_left :
%       ('a, 'b, Bigarray.c_layout) t ->
%       int -> ('a, 'b, Bigarray.c_layout) Bigarray.Array1.t
%   >>
%   
%                   Extract a row (one-dimensional slice) of the given
%                  two-dimensional  big array. The integer parameter is the
%                  index of the row to  extract. See
%                  Bigarray.Genarray.slice_left[29.1] for more details. 
%                  Array2.slice_left applies only to arrays with C layout.
% 
%   <<
%     val slice_right :
%       ('a, 'b, Bigarray.fortran_layout) t ->
%       int -> ('a, 'b, Bigarray.fortran_layout) Bigarray.Array1.t
%   >>
%   
%                   Extract a column (one-dimensional slice) of the given 
%                  two-dimensional big array. The integer parameter is the 
%                  index of the column to extract. See
%                  Bigarray.Genarray.slice_right[29.1]   for more details.
%                  Array2.slice_right applies only to arrays  with Fortran
%                  layout.
% 
%   <<
%     val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
%   >>
%   
%                   Copy the first big array to the second big array.  See
%                  Bigarray.Genarray.blit[29.1] for more details.
% 
%   <<
%     val fill : ('a, 'b, 'c) t -> 'a -> unit
%   >>
%   
%                   Fill the given big array with the given value.  See
%                  Bigarray.Genarray.fill[29.1] for more details.
% 
%   <<
%     val of_array :
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> 'a array array -> ('a, 'b, 'c) t
%   >>
%   
%                   Build a two-dimensional big array initialized from the 
%                  given array of arrays.
% 
%   <<
%     val map_file :
%       Unix.file_descr ->
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> bool -> int -> int -> ('a, 'b, 'c) t
%   >>
%   
%                   Memory mapping of a file as a two-dimensional big array. 
%                  See Bigarray.Genarray.map_file[29.1] for more details.
% 
%  
%  -  end
%  
%                Two-dimensional arrays. The Array2 structure provides
%               operations  similar to those of Bigarray.Genarray[29.1], but
%               specialized to the  case of two-dimensional arrays.
%  
%
%Three-dimensional arrays
%========================
%  
%<<
%  module Array3 : >>
%   
%    sig
% 
%  
%   <<
%     type ('a, 'b, 'c) t 
%   >>
%   
%                   The type of three-dimensional big arrays whose elements have
%                   Caml type 'a, representation kind 'b, and memory layout 'c.
% 
%   <<
%     val create :
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> int -> int -> int -> ('a, 'b, 'c) t
%   >>
%   
%                   Array3.create kind layout dim1 dim2 dim3 returns a new
%                  bigarray of  three dimension, whose size is dim1 in the first
%                  dimension,  dim2 in the second dimension, and dim3 in the
%                  third.  kind and layout determine the array element kind and 
%                  the array layout as described for
%                  Bigarray.Genarray.create[29.1].
% 
%   <<
%     val dim1 : ('a, 'b, 'c) t -> int
%   >>
%   
%                   Return the first dimension of the given three-dimensional
%                  big array.
% 
%   <<
%     val dim2 : ('a, 'b, 'c) t -> int
%   >>
%   
%                   Return the second dimension of the given three-dimensional
%                  big array.
% 
%   <<
%     val dim3 : ('a, 'b, 'c) t -> int
%   >>
%   
%                   Return the third dimension of the given three-dimensional
%                  big array.
% 
%   <<
%     val kind : ('a, 'b, 'c) t -> ('a, 'b) Bigarray.kind
%   >>
%   
%                   Return the kind of the given big array.
% 
%   <<
%     val layout : ('a, 'b, 'c) t -> 'c Bigarray.layout
%   >>
%   
%                   Return the layout of the given big array.
% 
%   <<
%     val get : ('a, 'b, 'c) t -> int -> int -> int -> 'a
%   >>
%   
%                   Array3.get a x y z, also written a.{x,y,z},  returns the
%                  element of a at coordinates (x, y, z).  x, y and z must be
%                  within the bounds of a,  as described for
%                  Bigarray.Genarray.get[29.1];   otherwise, Invalid_arg is
%                  raised.
% 
%   <<
%     val set : ('a, 'b, 'c) t -> int -> int -> int -> 'a -> unit
%   >>
%   
%                   Array3.set a x y v, or alternatively a.{x,y,z} <- v,  stores
%                  the value v at coordinates (x, y, z) in a.  x, y and z must
%                  be within the bounds of a,  as described for
%                  Bigarray.Genarray.set[29.1];  otherwise, Invalid_arg is
%                  raised.
% 
%   <<
%     val sub_left :
%       ('a, 'b, Bigarray.c_layout) t ->
%       int -> int -> ('a, 'b, Bigarray.c_layout) t
%   >>
%   
%                   Extract a three-dimensional sub'array of the given 
%                  three-dimensional big array by restricting the first
%                  dimension.  See Bigarray.Genarray.sub_left[29.1] for more
%                  details. Array3.sub_left  applies only to arrays with C
%                  layout.
% 
%   <<
%     val sub_right :
%       ('a, 'b, Bigarray.fortran_layout) t ->
%       int -> int -> ('a, 'b, Bigarray.fortran_layout) t
%   >>
%   
%                   Extract a three-dimensional sub'array of the given 
%                  three-dimensional big array by restricting the second
%                  dimension.  See Bigarray.Genarray.sub_right[29.1] for more
%                  details. Array3.sub_right  applies only to arrays with
%                  Fortran layout.
% 
%   <<
%     val slice_left_1 :
%       ('a, 'b, Bigarray.c_layout) t ->
%       int -> int -> ('a, 'b, Bigarray.c_layout) Bigarray.Array1.t
%   >>
%   
%                   Extract a one-dimensional slice of the given
%                  three-dimensional  big array by fixing the first two
%                  coordinates.  The integer parameters are the coordinates of
%                  the slice to  extract. See Bigarray.Genarray.slice_left[29.1]
%                  for more details.  Array3.slice_left_1 applies only to arrays
%                  with C layout.
% 
%   <<
%     val slice_right_1 :
%       ('a, 'b, Bigarray.fortran_layout) t ->
%       int -> int -> ('a, 'b, Bigarray.fortran_layout) Bigarray.Array1.t
%   >>
%   
%                   Extract a one-dimensional slice of the given
%                  three-dimensional  big array by fixing the last two
%                  coordinates.  The integer parameters are the coordinates of
%                  the slice to  extract. See
%                  Bigarray.Genarray.slice_right[29.1] for more details. 
%                  Array3.slice_right_1 applies only to arrays with Fortran 
%                  layout.
% 
%   <<
%     val slice_left_2 :
%       ('a, 'b, Bigarray.c_layout) t ->
%       int -> ('a, 'b, Bigarray.c_layout) Bigarray.Array2.t
%   >>
%   
%                   Extract a two-dimensional slice of the given
%                  three-dimensional  big array by fixing the first coordinate. 
%                  The integer parameter is the first coordinate of the slice to
%                   extract. See Bigarray.Genarray.slice_left[29.1] for more
%                  details.  Array3.slice_left_2 applies only to arrays with C
%                  layout.
% 
%   <<
%     val slice_right_2 :
%       ('a, 'b, Bigarray.fortran_layout) t ->
%       int -> ('a, 'b, Bigarray.fortran_layout) Bigarray.Array2.t
%   >>
%   
%                   Extract a two-dimensional slice of the given 
%                  three-dimensional big array by fixing the last coordinate. 
%                  The integer parameter is the coordinate of the slice  to
%                  extract. See Bigarray.Genarray.slice_right[29.1] for more
%                  details.  Array3.slice_right_2 applies only to arrays with
%                  Fortran  layout.
% 
%   <<
%     val blit : ('a, 'b, 'c) t -> ('a, 'b, 'c) t -> unit
%   >>
%   
%                   Copy the first big array to the second big array.  See
%                  Bigarray.Genarray.blit[29.1] for more details.
% 
%   <<
%     val fill : ('a, 'b, 'c) t -> 'a -> unit
%   >>
%   
%                   Fill the given big array with the given value.  See
%                  Bigarray.Genarray.fill[29.1] for more details.
% 
%   <<
%     val of_array :
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout -> 'a array array array -> ('a, 'b, 'c) t
%   >>
%   
%                   Build a three-dimensional big array initialized from the 
%                  given array of arrays of arrays.
% 
%   <<
%     val map_file :
%       Unix.file_descr ->
%       ('a, 'b) Bigarray.kind ->
%       'c Bigarray.layout ->
%       bool -> int -> int -> int -> ('a, 'b, 'c) t
%   >>
%   
%                   Memory mapping of a file as a three-dimensional big array. 
%                  See Bigarray.Genarray.map_file[29.1] for more details.
% 
%  
%  -  end
%  
%                Three-dimensional arrays. The Array3 structure provides
%               operations similar to those of  Bigarray.Genarray[29.1], but
%               specialized to the case of three-dimensional arrays.
%  
%
%Coercions between generic big arrays and fixed-dimension big arrays
%===================================================================
%  
%<<
%  val genarray_of_array1 : ('a, 'b, 'c) Array1.t -> ('a, 'b, 'c) Genarray.t
%>>
%    
%                Return the generic big array corresponding to the given
%               one-dimensional big array.
%  
%<<
%  val genarray_of_array2 : ('a, 'b, 'c) Array2.t -> ('a, 'b, 'c) Genarray.t
%>>
%    
%                Return the generic big array corresponding to the given
%               two-dimensional big array.
%  
%<<
%  val genarray_of_array3 : ('a, 'b, 'c) Array3.t -> ('a, 'b, 'c) Genarray.t
%>>
%    
%                Return the generic big array corresponding to the given
%               three-dimensional big array.
%  
%<<
%  val array1_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array1.t
%>>
%    
%                Return the one-dimensional big array corresponding to the given
%                generic big array. Raise Invalid_arg if the generic big array 
%               does not have exactly one dimension.
%  
%<<
%  val array2_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array2.t
%>>
%    
%                Return the two-dimensional big array corresponding to the given
%                generic big array. Raise Invalid_arg if the generic big array 
%               does not have exactly two dimensions.
%  
%<<
%  val array3_of_genarray : ('a, 'b, 'c) Genarray.t -> ('a, 'b, 'c) Array3.t
%>>
%    
%                Return the three-dimensional big array corresponding to the
%               given  generic big array. Raise Invalid_arg if the generic big
%               array  does not have exactly three dimensions.
%  
%
%Re-shaping big arrays
%=====================
%  
%<<
%  val reshape :
%    ('a, 'b, 'c) Genarray.t ->
%    int array -> ('a, 'b, 'c) Genarray.t
%>>
%    
%                reshape b [|d1;...;dN|] converts the big array b to a 
%               N-dimensional array of dimensions d1...dN. The returned  array
%               and the original array b share their data  and have the same
%               layout. For instance, assuming that b  is a one-dimensional
%               array of dimension 12, reshape b [|3;4|]  returns a
%               two-dimensional array b- of dimensions 3 and 4.  If b has C
%               layout, the element (x,y) of b- corresponds  to the element x *
%               3 + y of b. If b has Fortran layout,  the element (x,y) of b-
%               corresponds to the element  x + (y - 1) * 4 of b.  The returned
%               big array must have exactly the same number of  elements as the
%               original big array b. That is, the product  of the dimensions of
%               b must be equal to i1 * ... * iN.  Otherwise, Invalid_arg is
%               raised.
%  
%<<
%  val reshape_1 : ('a, 'b, 'c) Genarray.t -> int -> ('a, 'b, 'c) Array1.t
%>>
%    
%                Specialized version of Bigarray.reshape[29.1] for reshaping to
%               one-dimensional arrays.
%  
%<<
%  val reshape_2 :
%    ('a, 'b, 'c) Genarray.t ->
%    int -> int -> ('a, 'b, 'c) Array2.t
%>>
%    
%                Specialized version of Bigarray.reshape[29.1] for reshaping to
%               two-dimensional arrays.
%  
%<<
%  val reshape_3 :
%    ('a, 'b, 'c) Genarray.t ->
%    int -> int -> int -> ('a, 'b, 'c) Array3.t
%>>
%    
%                Specialized version of Bigarray.reshape[29.1] for reshaping to
%               three-dimensional arrays.
%  
%   
%  
%
%29.2  Big arrays in the Caml'c interface
%*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=
%
%  
%  C stub code that interface C or Fortran code with Caml code, as described in
%chapter 18, can exploit big arrays as follows.
%  
%
%29.2.1  Include file
%====================
%  
%  The include file <caml/bigarray.h> must be included in the C stub file. It
%declares the functions, constants and macros discussed below.
%  
%
%29.2.2  Accessing a Caml bigarray from C or Fortran
%===================================================
%  
%  If v is a Caml value representing a big array, the expression
%Data_bigarray_val(v) returns a pointer to the data part of the array. This
%pointer is of type void * and can be cast to the appropriate C type for the
%array (e.g. double [], char [][10], etc).
%  Various characteristics of the Caml big array can be consulted from C as
%follows: 
%                                         
%     --------------------------------------------------------------------
%     |               C expression                |       Returns        |
%     --------------------------------------------------------------------
%     |Bigarray_val(v)->num_dims                  |number of dimensions  |
%     |Bigarray_val(v)->dim[i]                    |i-th dimension        |
%     |Bigarray_val(v)->flags & BIGARRAY_KIND_MASK|kind of array elements|
%     --------------------------------------------------------------------
%   The kind of array elements is one of the following constants: 
%                                         
%        --------------------------------------------------------------
%        |     Constant      |              Element kind              |
%        --------------------------------------------------------------
%        |BIGARRAY_FLOAT32   |32'bit single-precision floats          |
%        |BIGARRAY_FLOAT64   |64'bit double-precision floats          |
%        |BIGARRAY_SINT8     |8'bit signed integers                   |
%        |BIGARRAY_UINT8     |8'bit unsigned integers                 |
%        |BIGARRAY_SINT16    |16'bit signed integers                  |
%        |BIGARRAY_UINT16    |16'bit unsigned integers                |
%        |BIGARRAY_INT32     |32'bit signed integers                  |
%        |BIGARRAY_INT64     |64'bit signed integers                  |
%        |BIGARRAY_CAML_INT  |31- or 63'bit signed integers           |
%        |BIGARRAY_NATIVE_INT|32- or 64'bit (platform-native) integers|
%        --------------------------------------------------------------
%   The following example shows the passing of a two-dimensional big array to a
%C function and a Fortran function. 
%<<
%      extern void my_c_function(double * data, int dimx, int dimy);
%      extern void my_fortran_function_(double * data, int * dimx, int * dimy);
%  
%      value caml_stub(value bigarray)
%      {
%        int dimx = Bigarray_val(bigarray)->dim[0];
%        int dimy = Bigarray_val(bigarray)->dim[1];
%        /* C passes scalar parameters by value */
%        my_c_function(Data_bigarray_val(bigarray), dimx, dimy);
%        /* Fortran passes all parameters by reference */
%        my_fortran_function_(Data_bigarray_val(bigarray), &dimx, &dimy);
%        return Val_unit;
%      }
%>>
%  
%  
%
%29.2.3  Wrapping a C or Fortran array as a Caml big array
%=========================================================
%  
%  A pointer p to an already'allocated C or Fortran array can be wrapped and
%returned to Caml as a big array using the alloc_bigarray or alloc_bigarray_dims
%functions. 
%  
% - alloc_bigarray(kind | layout, numdims, p, dims)
% Return a Caml big array wrapping the data pointed to by p. kind is the kind of
%   array elements (one of the BIGARRAY_ kind constants above). layout is
%   BIGARRAY_C_LAYOUT for an array with C layout and BIGARRAY_FORTRAN_LAYOUT for
%   an array with Fortran layout. numdims is the number of dimensions in the
%   array. dims is an array of numdims long integers, giving the sizes of the
%   array in each dimension.
% 
% - alloc_bigarray_dims(kind | layout, numdims, p, (long) dim_1, (long) dim_2,
%   ..., (long) dim_numdims)
% Same as alloc_bigarray, but the sizes of the array in each dimension are
%   listed as extra arguments in the function call, rather than being passed as
%   an array. 
%   The following example illustrates how statically-allocated C and Fortran
%arrays can be made available to Caml. 
%<<
%      extern long my_c_array[100][200];
%      extern float my_fortran_array_[300][400];
%  
%      value caml_get_c_array(value unit)
%      {
%        long dims[2];
%        dims[0] = 100; dims[1] = 200;
%        return alloc_bigarray(BIGARRAY_NATIVE_INT | BIGARRAY_C_LAYOUT,
%                              2, my_c_array, dims);
%      }
%  
%      value caml_get_fortran_array(value unit)
%      {
%        return alloc_bigarray_dims(BIGARRAY_FLOAT32 | BIGARRAY_FORTRAN_LAYOUT,
%                                   2, my_fortran_array_, 300L, 400L);
%      }
%>>
%  
%  
%