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#############################################################################
##
#W global.gd GAP library Steve Linton
##
#H @(#)$Id: global.gd,v 4.9 2002/04/15 10:04:42 sal Exp $
##
#Y Copyright (C) 1996, Lehrstuhl D fuer Mathematik, RWTH Aachen, Germany
#Y (C) 1998 School Math and Comp. Sci., University of St. Andrews, Scotland
#Y Copyright (C) 2002 The GAP Group
##
##
## This file contains the second stage of the "public" interface to
## the global variable namespace, allowing globals to be accessed and
## set by name.
##
## This is defined in two stages. global.g defines "capitalized" versions
## of the functions which do not use Info or other niceties and are not
## set up with InstallGlobalFunction. This can thus be read early, and
## the functions it defines can be used to define functions used to read
## more of the library.
##
## This file and global.gi stages install the really "public"
## functions and can be read later (once Info, DeclareGlobalFunction,
## etc are there)
##
## All of these functions give a warning if the global variable name
## contains characters not recognised as part of identifiers by the
## GAP parser
##
Revision.global_gd :=
"@(#)$Id: global.gd,v 4.9 2002/04/15 10:04:42 sal Exp $";
#############################################################################
##
#F IsValidIdentifier( <str> ) . . . check if a string is a valid identifier
##
## returns `true' if the string <str> would form a valid identifier
## consisting of letters, digits and underscores; otherwise it returns
## `false'. It does not check whether <str> contains characters escaped by a
## backslash `\\'.
##
DeclareGlobalFunction("IsValidIdentifier");
#############################################################################
##
#F ValueGlobal ( <name> ) . . . . . . . . . . . access a global by its name
##
## ValueGlobal ( <name> ) returns the value currently bound to the global
## variable named by the string <name>. An error is raised if no value
## is currently bound
##
DeclareGlobalFunction("ValueGlobal");
#############################################################################
##
#F IsBoundGlobal ( <name> ) . . . . . check if a global is bound by its name
##
## IsBoundGlobal ( <name> ) returns true if a value currently bound
## to the global variable named by the string <name> and false otherwise
##
DeclareGlobalFunction("IsBoundGlobal");
#############################################################################
##
#F UnbindGlobal ( <name> ) . . . . . . . . . . unbind a global by its name
##
## UnbindGlobal ( <name> ) removes any value currently bound
## to the global variable named by the string <name>. Nothing is returned
##
## A warning is given if <name> was not bound
## The global variable named by <name> must be writable,
## otherwise an error is raised.
##
DeclareGlobalFunction("UnbindGlobal");
#############################################################################
##
#F IsReadOnlyGlobal ( <name> ) . determine if a global variable is read-only
##
## IsReadOnlyGlobal ( <name> ) returns true if the global variable
## named by the string <name> is read-only and false otherwise (the default)
##
DeclareGlobalFunction("IsReadOnlyGlobal");
#############################################################################
##
#F MakeReadOnlyGlobal ( <name> ) . . . . . make a global variable read-only
##
## MakeReadOnlyGlobal ( <name> ) marks the global variable named
## by the string <name> as read-only.
##
## A warning is given if <name> has no value bound to it or if it is
## already read-only
##
DeclareGlobalFunction("MakeReadOnlyGlobal");
#############################################################################
##
#F MakeReadWriteGlobal ( <name> ) . . . . make a global variable read-write
##
## MakeReadWriteGlobal ( <name> ) marks the global variable named
## by the string <name> as read-write
##
## A warning is given if <name> is already read-write
##
DeclareGlobalFunction("MakeReadWriteGlobal");
#############################################################################
##
#F BindGlobal ( <name>, <val> ) . . . . . . sets a global variable `safely'
##
## BindGlobal ( <name>, <val> ) sets the global variable named by
## the string <name> to the value <val>, provided it was previously
## unbound, and makes it read-only. This is intended to be the normal
## way to create and set "official" global variable (such as
## Operations and Categories)
##
## An error is given if <name> already had a value bound.
##
DeclareGlobalFunction("BindGlobal");
#############################################################################
##
#F TemporaryGlobalVarName ( [<prefix>] ) name of an unbound global variable
##
## TemporaryGlobalVarName ( [<prefix>] ) returns a string that can be used
## as the name of a global variable that is not bound at the time when
## TemporaryGlobalVarName() is called. The optional argument prefix can
## specify a string with which the name of the global variable starts.
##
DeclareGlobalFunction("TemporaryGlobalVarName");
#############################################################################
##
#F HideGlobalVariables(<str1>[,<str2>,...]))
##
## temporarily makes global variables ``undefined''. The arguments to
## `HideGlobalVariables' are strings. If there is a global variable defined
## whose identifier is equal to one of the strings it will be ``hidden''.
## This means that identifier and value will be safely stored on a stack
## and the variable will be undefined afterwards. A call to
## `UnhideGlobalVariables' will restore the old values.
## The main purpose of hiding variables will be for the temporary creation
## of global variables for reading in data created by other programs.
DeclareGlobalFunction("HideGlobalVariables");
#############################################################################
##
#F UnhideGlobalVariables(<str1>[,<str2>,...]))
#F UnhideGlobalVariables()
##
## The second version unhides all variables that are still hidden.
DeclareGlobalFunction("UnhideGlobalVariables");
#############################################################################
##
#E global.gd . . . . . . . . . . . . . . . . . . . . . . . . . . . ends here
|
