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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/1998/REC-html40-19980424/loose.dtd">
<html lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>PicoLisp Reference</title>
<link rel="stylesheet" href="doc.css" type="text/css">
</head>
<body>
<a href="mailto:abu@software-lab.de">abu@software-lab.de</a>
<p align=right>
<i>Perfection is attained</i><br>
<i>not when there is nothing left to add</i><br>
<i>but when there is nothing left to take away</i><br>
<i>(Antoine de Saint-Exupéry)</i><br>
<h1>The PicoLisp Reference</h1>
<p align=right>(c) Software Lab. Alexander Burger
<p>This document describes the concepts, data types, and kernel functions of the
<a href="http://software-lab.de/down.html">PicoLisp</a> system.
<p>This is <i>not</i> a Lisp tutorial. For an introduction to Lisp, a
traditional Lisp book like "Lisp" by Winston/Horn (Addison-Wesley 1981) is
recommended. Note, however, that there are significant differences between
PicoLisp and Maclisp (and even greater differences to Common Lisp).
<p>Please take a look at the <a href="tut.html">PicoLisp Tutorial</a> for an
explanation of some aspects of PicoLisp, and scan through the list of <a
href="faq.html">Frequently Asked Questions (FAQ)</a>.
<p><ul>
<li><a href="#intro">Introduction</a>
<li><a href="#vm">The PicoLisp Machine</a>
<ul>
<li><a href="#cell">The Cell</a>
<li><a href="#data">Data Types</a>
<ul>
<li><a href="#number">Numbers</a>
<li><a href="#symbol">Symbols</a>
<ul>
<li><a href="#nilSym">NIL</a>
<li><a href="#internal">Internal Symbols</a>
<li><a href="#transient">Transient Symbols</a>
<li><a href="#external">External Symbols</a>
</ul>
<li><a href="#lst">Lists</a>
</ul>
<li><a href="#mem">Memory Management</a>
</ul>
<li><a href="#penv">Programming Environment</a>
<ul>
<li><a href="#inst">Installation</a>
<li><a href="#invoc">Invocation</a>
<li><a href="#io">Input/Output</a>
<ul>
<li><a href="#num-io">Numbers</a>
<li><a href="#sym-io">Symbols</a>
<ul>
<li><a href="#nilSym-io">NIL</a>
<li><a href="#internal-io">Internal Symbols</a>
<li><a href="#transient-io">Transient Symbols</a>
<li><a href="#external-io">External Symbols</a>
</ul>
<li><a href="#lst-io">Lists</a>
<li><a href="#macro-io">Read-Macros</a>
</ul>
<li><a href="#ev">Evaluation</a>
<li><a href="#int">Interrupt</a>
<li><a href="#coroutines">Coroutines</a>
<li><a href="#errors">Error Handling</a>
<li><a href="#atres">@ Result</a>
<li><a href="#cmp">Comparing</a>
<li><a href="#oop">OO Concepts</a>
<li><a href="#dbase">Database</a>
<ul>
<li><a href="#trans">Transactions</a>
<li><a href="#er">Entities / Relations</a>
</ul>
<li><a href="#pilog">Pilog (PicoLisp Prolog)</a>
<li><a href="#conv">Naming Conventions</a>
<li><a href="#trad">Breaking Traditions</a>
<li><a href="#bugs">Bugs</a>
</ul>
<li><a href="#fun">Function Reference</a>
<li><a href="#down">Download</a>
</ul>
<p><hr>
<h2><a name="intro">Introduction</a></h2>
<p>PicoLisp is the result of a language design study, trying to answer the
question "What is a minimal but useful architecture for a virtual machine?".
Because opinions differ about what is meant by "minimal" and "useful", there are
many answers to that question, and people might consider other solutions more
"minimal" or more "useful". But from a practical point of view, PicoLisp has
proven to be a valuable answer to that question.
<p>First of all, PicoLisp is a virtual machine architecture, and then a
programming language. It was designed in a "bottom up" way, and "bottom up" is
also the most natural way to understand and to use it: <i>Form Follows
Function</i>.
<p>PicoLisp has been used in several commercial and research programming
projects since 1988. Its internal structures are simple enough, allowing an
experienced programmer always to fully understand what's going on under the
hood, and its language features, efficiency and extensibility make it suitable
for almost any practical programming task.
<p>In a nutshell, emphasis was put on four design objectives. The PicoLisp
system should be
<p><dl>
<dt>Simple
<dd>The internal data structure should be as simple as possible. Only one single
data structure is used to build all higher level constructs.
<dt>Unlimited
<dd>There are no limits imposed upon the language due to limitations of the
virtual machine architecture. That is, there is no upper bound in symbol name
length, number digit counts, stack depth, or data structure and buffer sizes,
except for the total memory size of the host machine.
<dt>Dynamic
<dd>Behavior should be as dynamic as possible ("run"-time vs. "compile"-time).
All decisions are delayed until runtime where possible. This involves matters
like memory management, dynamic symbol binding, and late method binding.
<dt>Practical
<dd>PicoLisp is not just a toy of theoretical value. It is in use since 1988 in
actual application development, research and production.
</dl>
<p><hr>
<h2><a name="vm">The PicoLisp Machine</a></h2>
<p>An important point in the PicoLisp philosophy is the knowledge about the
architecture and data structures of the internal machinery. The high-level
constructs of the programming language directly map to that machinery, making
the whole system both understandable and predictable.
<p>This is similar to assembly language programming, where the programmer has
complete control over the machine.
<p><hr>
<h3><a name="cell">The Cell</a></h3>
<p>The PicoLisp virtual machine is both simpler and more powerful than most
current (hardware) processors. At the lowest level, it is constructed from a
single data structure called "cell":
<pre><code>
+-----+-----+
| CAR | CDR |
+-----+-----+
</code></pre>
<p>A cell is a pair of machine words, which traditionally are called CAR and CDR
in the Lisp terminology. These words can represent either a numeric value
(scalar) or the address of another cell (pointer). All higher level data
structures are built out of cells.
<p>The type information of higher level data is contained in the pointers to
these data. Assuming the implementation on a byte-addressed physical machine,
and a pointer size of typically 4 bytes, each cell has a size of 8 bytes.
Therefore, the pointer to a cell must point to an 8-byte boundary, and its
bit-representation will look like:
<pre><code>
xxxxxxxxxxxxxxxxxxxxxxxxxxxxx000
</code></pre>
<p>(the '<code>x</code>' means "don't care"). For the individual data types, the
pointer is adjusted to point to other parts of a cell, in effect setting some of
the lower three bits to non-zero values. These bits are then used by the
interpreter to determine the data type.
<p>In any case, bit(0) - the least significant of these bits - is reserved as a
mark bit for garbage collection.
<p>Initially, all cells in the memory are unused (free), and linked together to
form a "free list". To create higher level data types at runtime, cells are
taken from that free list, and returned by the garbage collector when they are
no longer needed. All memory management is done via that free list; there are no
additional buffers, string spaces or special memory areas, with two exceptions:
<p><ul>
<li>A certain fixed area of memory is set aside to contain the executable code
and global variables of the interpreter itself, and
<li>a standard push down stack for return addresses and temporary storage. Both
are not directly accessible by the programmer).
</ul>
<p><hr>
<h3><a name="data">Data Types</a></h3>
<p>On the virtual machine level, PicoLisp supports
<p><ul>
<li>three base data types: Numbers, Symbols and Cons Pairs (Lists),
<li>the three scope variations of symbols: Internal, Transient and External, and
<li>the special symbol <code>NIL</code>.
</ul>
<p>They are all built from the single cell data structure, and all runtime data
cannot consist of any other types than these three.
<p>The following diagram shows the complete data type hierarchy, consisting of
the three base types and the symbol variations:
<pre><code>
cell
|
+--------+--------+
| | |
Number Symbol Pair
|
|
+--------+--------+--------+
| | | |
NIL Internal Transient External
</code></pre>
<p><hr>
<h4><a name="number">Numbers</a></h4>
<p>A number can represent a signed integral value of arbitrary size. The CARs of
one or more cells hold the number's "digits" (each in the machine's word size),
to store the number's binary representation.
<pre><code>
Number
|
V
+-----+-----+
| DIG | | |
+-----+--+--+
|
V
+-----+-----+
| DIG | | |
+-----+--+--+
|
V
...
</code></pre>
<p>The first cell holds the least significant digit. The least significant bit
of that digit represents the sign.
<p>The pointer to a number points into the middle of the CAR, with an offset of
2 from the cell's start address. Therefore, the bit pattern of a number will be:
<pre><code>
xxxxxxxxxxxxxxxxxxxxxxxxxxxxx010
</code></pre>
<p>Thus, a number is recognized by the interpreter when bit(1) is non-zero.
<p><hr>
<h4><a name="symbol">Symbols</a></h4>
<p>A symbol is more complex than a number. Each symbol has a value, and
optionally a name and an arbitrary number of properties. The CDR of a symbol
cell is also called VAL, and the CAR points to the symbol's tail. As a minimum,
a symbol consists of a single cell, and has no name or properties:
<pre><code>
Symbol
|
V
+-----+-----+
| / | VAL |
+-----+-----+
</code></pre>
<p>That is, the symbol's tail is empty (points to <code>NIL</code>, as indicated
by the '<code>/</code>' character).
<p>The pointer to a symbol points to the CDR of the cell, with an offset of 4
from the cell's start address. Therefore, the bit pattern of a symbol will be:
<pre><code>
xxxxxxxxxxxxxxxxxxxxxxxxxxxxx100
</code></pre>
<p>Thus, a symbol is recognized by the interpreter when bit(2) is non-zero.
<p>A property is a key-value pair, represented by a cons pair in the symbol's
tail. This is called a "property list". The property list may be terminated by a
number representing the symbol's name. In the following example, a symbol with
the name <code>"abc"</code> has three properties: A KEY/VAL pair, a cell with
only a KEY, and another KEY/VAL pair.
<pre><code>
Symbol
|
V
+-----+-----+
| | | VAL |
+--+--+-----+
| tail
|
V name
+-----+-----+ +-----+-----+ +-----+-----+ +-----+-----+
| | | ---+---> | KEY | ---+---> | | | ---+---> |'cba'| / |
+--+--+-----+ +-----+-----+ +--+--+-----+ +-----+-----+
| |
V V
+-----+-----+ +-----+-----+
| VAL | KEY | | VAL | KEY |
+-----+-----+ +-----+-----+
</code></pre>
<p>Each property in a symbol's tail is either a symbol (like the single KEY
above, then it represents the boolean value <code>T</code>), or a cons pair with
the property key in its CDR and the property value in its CAR. In both cases,
the key should be a symbol, because searches in the property list are performed
using pointer comparisons.
<p>The name of a symbol is stored as a number at the end of the tail. It
contains the characters of the name in UTF-8 encoding, using between one and
three 8-bit-bytes per character. The first byte of the first character is stored
in the lowest 8 bits of the number.
<p>All symbols have the above structure, but depending on scope and
accessibility there are actually four types of symbols: <code><a
href="#nilSym">NIL</a></code>, <a href="#internal">internal</a>, <a
href="#transient">transient</a> and <a href="#external">external</a> symbols.
<p><hr>
<h5><a name="nilSym">NIL</a></h5>
<p><code>NIL</code> is a special symbol which exists exactly once in the whole
system. It is used
<p><ul>
<li>as an end-of-list marker
<li>to represent the empty list
<li>to represent the boolean value "false"
<li>to represent the absolute minimum
<li>to represent a string of length zero
<li>to represent the value "Not a Number"
<li>as the root of all class hierarchies
</ul>
<p>For that, <code>NIL</code> has a special structure:
<pre><code>
NIL: /
|
V
+-----+-----+-----+-----+
| / | / | / | / |
+-----+--+--+-----+-----+
</code></pre>
<p>The reason for that structure is <code>NIL</code>'s dual nature both as a
symbol and as a list:
<p><ul>
<li>As a symbol, it should give <code>NIL</code> for its VAL, and be without
properties
<li>For the empty list, <code>NIL</code> should give <code>NIL</code> both for
its CAR and for its CDR
</ul>
<p>These requirements are fulfilled by the above structure.
<p><hr>
<h5><a name="internal">Internal Symbols</a></h5>
<p>Internal Symbols are all those "normal" symbols, as they are used for
function definitions and variable names. They are "interned" into an index
structure, so that it is possible to find an internal symbol by searching for
its name.
<p>There cannot be two different internal symbols with the same name.
<p>Initially, a new internal symbol's VAL is <code>NIL</code>.
<p><hr>
<h5><a name="transient">Transient Symbols</a></h5>
<p>Transient symbols are only interned into a index structure for a certain time
(e.g. while reading the current source file), and are released after that. That
means, a transient symbol cannot be accessed then by its name, and there may be
several transient symbols in the system having the same name.
<p>Transient symbols are used
<p><ul>
<li>as text strings
<li>as identifiers with a limited access scope (like, for example,
<code>static</code> identifiers in the C language family)
<li>as anonymous, dynamically created objects (without a name)
</ul>
<p>Initially, a new transient symbol's VAL is that symbol itself.
<p>A transient symbol without a name can be created with the <code><a
href="refB.html#box">box</a></code> or <code><a
href="refN.html#new">new</a></code> functions.
<p><hr>
<h5><a name="external">External Symbols</a></h5>
<p>External symbols reside in a database file (or a similar resources, see
<code><a href="refE.html#*Ext">*Ext</a></code>), and are loaded into memory -
and written back to the file - dynamically as needed, and transparently to the
programmer. They are kept in memory ("cached") as long as they are accessible
("referred to") from other parts of the program, or when they were modified but
not yet written to the database file (by <code><a
href="refC.html#commit">commit</a></code>).
<p>The interpreter recognizes external symbols internally by an additional tag
bit in the tail structure.
<p>There cannot be two different external symbols with the same name. External
symbols are maintained in index structures while they are loaded into memory,
and have their external location (disk file and block offset) directly coded
into their names (more details <a href="#external-io">here</a>).
<p>Initially, a new external symbol's VAL is <code>NIL</code>, unless otherwise
specified at creation time.
<p><hr>
<h4><a name="lst">Lists</a></h4>
<p>A list is a sequence of one or more cells (cons pairs), holding numbers,
symbols, or cons pairs.
<pre><code>
|
V
+-----+-----+
| any | | |
+-----+--+--+
|
V
+-----+-----+
| any | | |
+-----+--+--+
|
V
...
</code></pre>
<p>Lists are used in PicoLisp to emulate composite data structures like arrays,
trees, stacks or queues.
<p>In contrast to lists, numbers and symbols are collectively called "Atoms".
<p>Typically, the CDR of each cell in a list points to the following cell,
except for the last cell which points to <code>NIL</code>. If, however, the CDR of
the last cell points to an atom, that cell is called a "dotted pair" (because of
its I/O syntax with a dot '<code>.</code>' between the two values).
<p><hr>
<h3><a name="mem">Memory Management</a></h3>
<p>The PicoLisp interpreter has complete knowledge of all data in the system,
due to the type information associated with every pointer. Therefore, an
efficient garbage collector mechanism can easily be implemented. PicoLisp
employs a simple but fast mark-and-sweep garbage collector.
<p>As the collection process is very fast (in the order of milliseconds per
megabyte), it was not necessary to develop more complicated, time-consuming and
error-prone garbage collection algorithms (e.g. incremental collection). A
compacting garbage collector is also not necessary, because the single cell data
type cannot cause heap fragmentation.
<p><hr>
<h2><a name="penv">Programming Environment</a></h2>
<p>Lisp was chosen as the programming language, because of its clear and simple
structure.
<p>In some previous versions, a Forth-like syntax was also implemented on top of
a similar virtual machine (Lifo). Though that language was more flexible and
expressive, the traditional Lisp syntax proved easier to handle, and the virtual
machine can be kept considerably simpler.
PicoLisp inherits the major advantages of classical Lisp systems like
<p><ul>
<li>Dynamic data types and structures
<li>Formal equivalence of code and data
<li>Functional programming style
<li>An interactive environment
</ul>
<p>In the following, some concepts and peculiarities of the PicoLisp language
and environment are described.
<p><hr>
<h3><a name="inst">Installation</a></h3>
<p>PicoLisp supports two installation strategies: Local and Global.
<p>Normally, if you didn't build PicoLisp yourself but installed it with your
operating system's package manager, you will have a global installation. This
allows system-wide access to the executable and library/documentation files.
<p>To get a local installation, you can directly download the PicoLisp tarball,
and follow the instructions in the INSTALL file.
<p>A local installation will not interfere in any way with the world outside its
directory. There is no need to touch any system locations, and you don't have to
be root to install it. Many different versions - or local modifications - of
PicoLisp can co-exist on a single machine.
<p>Note that you are still free to have local installations along with a global
installation, and invoke them explicitly as desired.
<p>Most examples in the following apply to a global installation.
<p><hr>
<h3><a name="invoc">Invocation</a></h3>
<p>When PicoLisp is invoked from the command line, an arbitrary number of
arguments may follow the command name.
<p>By default, each argument is the name of a file to be executed by the
interpreter. If, however, the argument's first character is a hyphen
'<code>-</code>', then the rest of that argument is taken as a Lisp function
call (without the surrounding parentheses), and a hyphen by itself as an
argument stops evaluation of the rest of the command line (it may be processed
later using the <code><a href="refA.html#argv">argv</a></code> and <code><a
href="refO.html#opt">opt</a></code> functions). This whole mechanism corresponds
to calling <code>(<a href="refL.html#load">load</a> T)</code>.
<p>A special case is if the last argument is a single '<code>+</code>'. This
will switch on debug mode (the <code><a href="refD.html#*Dbg">*Dbg</a></code>
global variable) and discard the '<code>+</code>'.
<p>As a convention, PicoLisp source files have the extension "<code>.l</code>".
<p>Note that the PicoLisp executable itself does not expect or accept any
command line flags or options (except the '<code>+</code>', see above). They are
reserved for application programs.
<p>The simplest and shortest invocation of PicoLisp does nothing, and exits
immediately by calling <code><a href="refB.html#bye">bye</a></code>:
<pre><code>
$ picolisp -bye
$
</code></pre>
<p>In interactive mode, the PicoLisp interpreter (see <code><a
href="refL.html#load">load</a></code>) will also exit when <code>Ctrl-D</code>
is entered:
<pre><code>
$ picolisp
: $ # Typed Ctrl-D
</code></pre>
<p>To start up the standard PicoLisp environment, several files should be
loaded. The most commonly used things are in "lib.l" and in a bunch of other
files, which are in turn loaded by "ext.l". Thus, a typical call would be:
<pre><code>
$ picolisp lib.l ext.l
</code></pre>
<p>The recommended way, however, is to call the "pil" shell script, which
includes "lib.l" and "ext.l". Given that your current project is loaded by some
file "myProject.l" and your startup function is <code>main</code>, your
invocation would look like:
<pre><code>
$ pil myProject.l -main
</code></pre>
<p>For interactive development it is recommended to enable debugging mode, to
get the vi-style command line editor, single-stepping, tracing and other
debugging utilities.
<pre><code>
$ pil myProject.l -main +
</code></pre>
<p>This is - in a local installation - equivalent to
<pre><code>
$ ./dbg myProject.l -main
</code></pre>
<p>or
<pre><code>
$ ./pil myProject.l -main +
</code></pre>
<p>In any case, the directory part of the first file name supplied (normally,
the path to "lib.l" as called by 'pil' or 'dbg') is remembered internally as the
<i>PicoLisp Home Directory</i>. This path is later automatically substituted for
any leading "<code>@</code>" character in file name arguments to I/O functions
(see <code><a href="refP.html#path">path</a></code>).
<p><hr>
<h3><a name="io">Input/Output</a></h3>
<p>In Lisp, each internal data structure has a well-defined external
representation in human-readable format. All kinds of data can be written to a
file, and restored later to their original form by reading that file.
<p>In normal operation, the PicoLisp interpreter continuously executes an
infinite "read-eval-print loop". It reads one expression at a time, evaluates
it, and prints the result to the console. Any input into the system, like data
structures and function definitions, is done in a consistent way no matter
whether it is entered at the console or read from a file.
<p>Comments can be embedded in the input stream with the hash <code>#</code>
character. Everything up to the end of that line will be ignored by the reader.
<pre><code>
: (* 1 2 3) # This is a comment
-> 6
</code></pre>
<p>A comment spanning several lines may be enclosed between <code>#{</code> and
<code>}#</code>.
<p>Here is the I/O syntax for the individual PicoLisp data types (numbers,
symbols and lists) and for read-macros:
<p><hr>
<h4><a name="num-io">Numbers</a></h4>
<p>A number consists of an arbitrary number of digits ('<code>0</code>' through
'<code>9</code>'), optionally preceded by a sign character ('<code>+</code>' or
'<code>-</code>'). Legal number input is:
<pre><code>
: 7
-> 7
: -12345678901245678901234567890
-> -12345678901245678901234567890
</code></pre>
<p>Fixpoint numbers can be input by embedding a decimal point '<code>.</code>',
and setting the global variable <code><a href="refS.html#*Scl">*Scl</a></code>
appropriately:
<pre><code>
: *Scl
-> 0
: 123.45
-> 123
: 456.78
-> 457
: (setq *Scl 3)
-> 3
: 123.45
-> 123450
: 456.78
-> 456780
</code></pre>
<p>Thus, fixpoint input simply scales the number to an integer value
corresponding to the number of digits in <code><a
href="refS.html#*Scl">*Scl</a></code>.
<p>Formatted output of scaled fixpoint values can be done with the <code><a
href="refF.html#format">format</a></code> and <code><a
href="refR.html#round">round</a></code> functions:
<pre><code>
: (format 1234567890 2)
-> "12345678.90"
: (format 1234567890 2 "." ",")
-> "12,345,678.90"
</code></pre>
<p><hr>
<h4><a name="sym-io">Symbols</a></h4>
<p>The reader is able to recognize the individual symbol types from their
syntactic form. A symbol name should - of course - not look like a legal number
(see above).
<p>In general, symbol names are case-sensitive. <code>car</code> is not the same
as CAR.
<p><hr>
<h5><a name="nilSym-io">NIL</a></h5>
<p>Besides for standard normal form, <code>NIL</code> is also recognized as
<code>()</code>, <code>[]</code> or <code>""</code>.
<pre><code>
: NIL
-> NIL
: ()
-> NIL
: ""
-> NIL
</code></pre>
<p>Output will always appear as <code>NIL</code>.
<p><hr>
<h5><a name="internal-io">Internal Symbols</a></h5>
<p>Internal symbol names can consist of any printable (non-whitespace)
character, except for the following meta characters:
<pre><code>
" ' ( ) , [ ] ` ~ { }
</code></pre>
<p>It is possible, though, to include these special characters into symbol names
by escaping them with a backslash '<code>\</code>'.
<p>The dot '<code>.</code>' has a dual nature. It is a meta character when
standing alone, denoting a <a href="#dotted">dotted pair</a>, but can otherwise
be used in symbol names.
<p>As a rule, anything not recognized by the reader as another data type will be
returned as an internal symbol.
<p><hr>
<h5><a name="transient-io">Transient Symbols</a></h5>
<p>A transient symbol is anything surrounded by double quotes '<code>"</code>'.
With that, it looks - and can be used - like a string constant in other
languages. However, it is a real symbol, and may be assigned a value or a
function definition, and properties.
<p>Initially, a transient symbol's value is that symbol itself, so that it does
not need to be quoted for evaluation:
<p><pre><code>
: "This is a string"
-> "This is a string"
</code></pre>
<p>However, care must be taken when assigning a value to a transient symbol.
This may cause unexpected behavior:
<p><pre><code>
: (setq "This is a string" 12345)
-> 12345
: "This is a string"
-> 12345
</code></pre>
<p>The name of a transient symbol can contain any character except the
null-byte. A double quote character can be escaped with a backslash
'<code>\</code>', and a backslash itself has to be escaped with another
backslash. Control characters can be written with a preceding hat
'<code>^</code>' character.
<p><pre><code>
: "We^Ird\\Str\"ing"
-> "We^Ird\\Str\"ing"
: (chop @)
-> ("W" "e" "^I" "r" "d" "\\" "S" "t" "r" "\"" "i" "n" "g")
</code></pre>
<p>The index for transient symbols is cleared automatically before and after
<code><a href="refL.html#load">load</a></code>ing a source file, or it can be
reset explicitly with the <code><a href="ref_.html#====">====</a></code>
function. With that mechanism, it is possible to create symbols with a local
access scope, not accessible from other parts of the program.
<p>A special case of transient symbols are <i>anonymous symbols</i>. These are
symbols without name (see <code><a href="refB.html#box">box</a></code>, <code><a
href="refB.html#box?">box?</a></code> or <code><a
href="refN.html#new">new</a></code>). They print as a dollar sign
(<code>$</code>) followed by a decimal digit string (actually their machine
address).
<p><hr>
<h5><a name="external-io">External Symbols</a></h5>
<p>External symbol names are surrounded by braces ('<code>{</code>' and
'<code>}</code>'). The characters of the symbol's name itself identify the
physical location of the external object. This is
<ul>
<li>in the 32-bit version: The number of the database file, and - separated by a
hyphen - the starting block in the database file. Both numbers are encoded in
base-64 notation (characters '<code>0</code>' through '<code>9</code>',
'<code>:</code>', '<code>;</code>', '<code>A</code>' through '<code>Z</code>'
and '<code>a</code>' through '<code>z</code>').
<li>in the 64-bit version: The number of the database file minus 1 in "hax"
notation (i.e. hexadecimal/alpha notation, where '<code>@</code>' is zero,
'<code>A</code>' is 1 and '<code>O</code>' is 15 (from "alpha" to "omega")),
immediately followed (without a hyphen) the starting block in octal
('<code>0</code>' through '<code>7</code>').
</ul>
<p>In both cases, the database file (and possibly the hypen) are omitted for the
first (default) file.
<p><hr>
<h4><a name="lst-io">Lists</a></h4>
<p>Lists are surrounded by parentheses ('<code>(</code>' and '<code>)</code>').
<p><code>(A)</code> is a list consisting of a single cell, with the symbol
<code>A</code> in its CAR, and <code>NIL</code> in its CDR.
<p><code>(A B C)</code> is a list consisting of three cells, with the symbols
<code>A</code>, <code>B</code> and <code>C</code> respectively in their CAR, and
<code>NIL</code> in the last cell's CDR.
<p><a name="dotted"><code>(A . B)</code></a> is a "dotted pair", a list
consisting of a single cell, with the symbol <code>A</code> in its CAR, and
<code>B</code> in its CDR.
<p>PicoLisp has built-in support for reading and printing simple circular lists.
If the dot in a dotted-pair notation is immediately followed by a closing
parenthesis, it indicates that the CDR of the last cell points back to the
beginning of that list.
<pre><code>
: (let L '(a b c) (conc L L))
-> (a b c .)
: (cdr '(a b c .))
-> (b c a .)
: (cddddr '(a b c .))
-> (b c a .)
</code></pre>
<p>A similar result can be achieved with the function <code><a
href="refC.html#circ">circ</a></code>. Such lists must be used with care,
because many functions won't terminate or will crash when given such a list.
<p><hr>
<h4><a name="macro-io">Read-Macros</a></h4>
<p>Read-macros in PicoLisp are special forms that are recognized by the reader,
and modify its behavior. Note that they take effect immediately while <code><a
href="refR.html#read">read</a></code>ing an expression, and are not seen by the
<code>eval</code> in the main loop.
<p>The most prominent read-macro in Lisp is the single quote character
<code>'</code>, which expands to a call of the <code><a
href="refQ.html#quote">quote</a></code> function. Note that the single quote
character is also printed instead of the full function name.
<pre><code>
: '(a b c)
-> (a b c)
: '(quote . a)
-> 'a
: (cons 'quote 'a) # (quote . a)
-> 'a
: (list 'quote 'a) # (quote a)
-> '(a)
</code></pre>
<p>A comma (<code>,</code>) will cause the reader to collect the following data
item into an <code><a href="refI.html#idx">idx</a></code> tree in the global
variable <code><a href="refU.html#*Uni">*Uni</a></code>, and to return a
previously inserted equal item if present. This makes it possible to create a
unique list of references to data which do normally not follow the rules of
pointer equality. If the value of <code>*Uni</code> is <code>T</code>, the
comma read macro mechanism is disabled.
<p>A single backquote character <code>`</code> will cause the reader to evaluate
the following expression, and return the result.
<pre><code>
: '(a `(+ 1 2 3) z)
-> (a 6 z)
</code></pre>
<p>A tilde character <code>~</code> inside a list will cause the reader to
evaluate the following expression, and (destructively) splice the result into
the list.
<pre><code>
: '(a b c ~(list 'd 'e 'f) g h i)
-> (a b c d e f g h i)
</code></pre>
<p>When a tilde character is used to separate two symbol names (without
surrounding whitespace), the first is taken as a namespace to look up the second
(64-bit version only).
<pre><code>
: 'libA~foo # Look up 'foo' in namespace 'libA'
-> "foo" # "foo" is not interned in the current namespace
</code></pre>
<p>Reading <code>libA~foo</code> is equivalent to switching the current
namespace to <code>libA</code> (with <code><a
href="refS.html#symbols">symbols</a></code>), reading the symbol
<code>foo</code>, and then switching back to the original namespace.
<p>Brackets ('<code>[</code>' and '<code>]</code>') can be used as super
parentheses. A closing bracket will match the innermost opening bracket, or all
currently open parentheses.
<pre><code>
: '(a (b (c (d]
-> (a (b (c (d))))
: '(a (b [c (d]))
-> (a (b (c (d))))
</code></pre>
<p>Finally, reading the sequence '<code>{}</code>' will result in a new
anonymous symbol with value <code>NIL</code>, equivalent to a call to <code><a
href="refB.html#box">box</a></code> without arguments.
<pre><code>
: '({} {} {})
-> ($134599965 $134599967 $134599969)
: (mapcar val @)
-> (NIL NIL NIL)
</code></pre>
<p><hr>
<h3><a name="ev">Evaluation</a></h3>
<p>PicoLisp tries to evaluate any expression encountered in the read-eval-print
loop. Basically, it does so by applying the following three rules:
<p><ul>
<li>A number evaluates to itself.
<li>A symbol evaluates to its value (VAL).
<li>A list is evaluated as a function call, with the CAR as the function and the
CDR the arguments to that function. These arguments are in turn evaluated
according to these three rules.
</ul>
<pre><code>
: 1234
-> 1234 # Number evaluates to itself
: *Pid
-> 22972 # Symbol evaluates to its VAL
: (+ 1 2 3)
-> 6 # List is evaluated as a function call
</code></pre>
<p>For the third rule, however, things get a bit more involved. First - as a
special case - if the CAR of the list is a number, the whole list is returned as
it is:
<pre><code>
: (1 2 3 4 5 6)
-> (1 2 3 4 5 6)
</code></pre>
<p>This is not really a function call but just a convenience to avoid having to
quote simple data lists.
<p>Otherwise, if the CAR is a symbol or a list, PicoLisp tries to obtain an
executable function from that, by either using the symbol's value, or by
evaluating the list.
<p>What is an executable function? Or, said in another way, what can be applied
to a list of arguments, to result in a function call? A legal function in
PicoLisp is
<p><dl>
<dt>either
<dd>a <i>number</i>. When a number is used as a function, it is simply taken as
a pointer to executable code that will be called with the list of (unevaluated)
arguments as its single parameter. It is up to that code to evaluate the
arguments, or not. Some functions do not evaluate their arguments (e.g.
<code>quote</code>) or evaluate only some of their arguments (e.g.
<code>setq</code>).
<dt>or
<dd>a <i>lambda expression</i>. A lambda expression is a list, whose CAR is
either a symbol or a list of symbols, and whose CDR is a list of expressions.
Note: In contrast to other Lisp implementations, the symbol LAMBDA itself does
not exist in PicoLisp but is implied from context.
</dl>
<p>A few examples should help to understand the practical consequences of these
rules. In the most common case, the CAR will be a symbol defined as a function,
like the <code>*</code> in:
<pre><code>
: (* 1 2 3) # Call the function '*'
-> 6
</code></pre>
<p>Inspecting the VAL of <code>*</code> gives
<pre><code>
: * # Get the VAL of the symbol '*'
-> 67318096
</code></pre>
<p>The VAL of <code>*</code> is a number. In fact, it is the numeric
representation of a C-function pointer, i.e. a pointer to executable code. This
is the case for all built-in functions of PicoLisp.
<p>Other functions in turn are written as Lisp expressions:
<pre><code>
: (de foo (X Y) # Define the function 'foo'
(* (+ X Y) (+ X Y)) )
-> foo
: (foo 2 3) # Call the function 'foo'
-> 25
: foo # Get the VAL of the symbol 'foo'
-> ((X Y) (* (+ X Y) (+ X Y)))
</code></pre>
<p>The VAL of <code>foo</code> is a list. It is the list that was assigned to
<code>foo</code> with the <code>de</code> function. It would be perfectly legal
to use <code>setq</code> instead of <code>de</code>:
<pre><code>
: (setq foo '((X Y) (* (+ X Y) (+ X Y))))
-> ((X Y) (* (+ X Y) (+ X Y)))
: (foo 2 3)
-> 25
</code></pre>
<p>If the VAL of <code>foo</code> were another symbol, that symbol's VAL would
be used instead to search for an executable function.
<p>As we said above, if the CAR of the evaluated expression is not a symbol but
a list, that list is evaluated to obtain an executable function.
<pre><code>
: ((intern (pack "c" "a" "r")) (1 2 3))
-> 1
</code></pre>
<p>Here, the <code>intern</code> function returns the symbol <code>car</code>
whose VAL is used then. It is also legal, though quite dangerous, to use the
code-pointer directly:
<pre><code>
: *
-> 67318096
: ((* 2 33659048) 1 2 3)
-> 6
: ((quote . 67318096) 1 2 3)
-> 6
: ((quote . 1234) (1 2 3))
Segmentation fault
</code></pre>
<p>When an executable function is defined in Lisp itself, we call it a <a
name="lambda"><i>lambda expression</i></a>. A lambda expression always has a
list of executable expressions as its CDR. The CAR, however, must be a either a
list of symbols, or a single symbol, and it controls the evaluation of the
arguments to the executable function according to the following rules:
<p><dl>
<dt>When the CAR is a list of symbols
<dd>For each of these symbols an argument is evaluated, then the symbols are
bound simultaneously to the results. The body of the lambda expression is
executed, then the VAL's of the symbols are restored to their original values.
This is the most common case, a fixed number of arguments is passed to the
function.
<dt>Otherwise, when the CAR is the symbol <code>@</code>
<dd>All arguments are evaluated and the results kept internally in a list. The
body of the lambda expression is executed, and the evaluated arguments can be
accessed sequentially with the <code><a href="refA.html#args">args</a></code>,
<code><a href="refN.html#next">next</a></code>, <code><a
href="refA.html#arg">arg</a></code> and <code><a
href="refR.html#rest">rest</a></code> functions. This allows to define functions
with a variable number of evaluated arguments.
<dt>Otherwise, when the CAR is a single symbol
<dd>The symbol is bound to the whole unevaluated argument list. The body of the
lambda expression is executed, then the symbol is restored to its original
value. This allows to define functions with unevaluated arguments. Any kind of
interpretation and evaluation of the argument list can be done inside the
expression body.
</dl>
<p>In all cases, the return value is the result of the last expression in the
body.
<pre><code>
: (de foo (X Y Z) # CAR is a list of symbols
(list X Y Z) ) # Return a list of all arguments
-> foo
: (foo (+ 1 2) (+ 3 4) (+ 5 6))
-> (3 7 11) # all arguments are evaluated
</code></pre>
<pre><code>
: (de foo X # CAR is a single symbol
X ) # Return the argument
-> foo
: (foo (+ 1 2) (+ 3 4) (+ 5 6))
-> ((+ 1 2) (+ 3 4) (+ 5 6)) # the whole unevaluated list is returned
</code></pre>
<pre><code>
: (de foo @ # CAR is the symbol '@'
(list (next) (next) (next)) ) # Return the first three arguments
-> foo
: (foo (+ 1 2) (+ 3 4) (+ 5 6))
-> (3 7 11) # all arguments are evaluated
</code></pre>
<p>Note that these forms can also be combined. For example, to evaluate only the
first two arguments, bind the results to <code>X</code> and <code>Y</code>, and
bind all other arguments (unevaluated) to <code>Z</code>:
<pre><code>
: (de foo (X Y . Z) # CAR is a list with a dotted-pair tail
(list X Y Z) ) # Return a list of all arguments
-> foo
: (foo (+ 1 2) (+ 3 4) (+ 5 6))
-> (3 7 ((+ 5 6))) # Only the first two arguments are evaluated
</code></pre>
<p>Or, a single argument followed by a variable number of arguments:
<pre><code>
: (de foo (X . @) # CAR is a dotted-pair with '@'
(println X) # print the first evaluated argument
(while (args) # while there are more arguments
(println (next)) ) ) # print the next one
-> foo
: (foo (+ 1 2) (+ 3 4) (+ 5 6))
3 # X
7 # next argument
11 # and the last argument
-> 11
</code></pre>
<p>In general, if more than the expected number of arguments is supplied to a
function, these extra arguments will be ignored. Missing arguments default to
<code>NIL</code>.
<p><hr>
<h3><a name="coroutines">Coroutines</a></h3>
<p>Coroutines are independent execution contexts. They may have multiple entry
and exit points, and preserve their environment between invocations.
<p>They are available only in the 64-bit version.
<p>A coroutine is identified by a tag. This tag can be passed to other
functions, and (re)invoked as needed. In this regard coroutines are similar to
"continuations" in other languages.
<p>When the tag goes out of scope while it is not actively running, the
coroutine will be garabage collected. In cases where this is desired, using a <a
href="#transient">transient</a> symbol for the tag is recommended.
<p>A coroutine is created by calling <code><a href="refC.html#co">co</a></code>.
Its <code>prg</code> body will be executed, and unless <code><a
href="refY.html#yield">yield</a></code> is called at some point, the coroutine
will "fall off" at the end and disappear.
<p>When <code><a href="refY.html#yield">yield</a></code> is called, control is
either transferred back to the caller, or to some other - explicitly specified,
and already running - coroutine.
<p>A coroutine is stopped and disposed when
<p><ul>
<li>execution falls off the end
<li>some other (co)routine calls <code><a href="refC.html#co">co</a></code> with
that tag but without a <code>prg</code> body
<li>a <code><a href="refT.html#throw">throw</a></code> into another (co)routine
environment is executed
<li>an error occurred, and <a href="#errors">error handling</a> was entered
</ul>
<p>In the current implementation, not more than 64 coroutines can exist at the
same time. Reentrant coroutines are not supported, a coroutine cannot resume
itself directly or indirectly.
<p><hr>
<h3><a name="int">Interrupt</a></h3>
<p>During the evaluation of an expression, the PicoLisp interpreter can be
interrupted at any time by hitting <code>Ctrl-C</code>. It will then enter the
breakpoint routine, as if <code><a href="ref_.html#!">!</a></code> were called.
<p>Hitting ENTER at that point will continue evaluation, while <code>(<a
href="refQ.html#quit">quit</a>)</code> will abort evaluation and return the
interpreter to the top level. See also <code><a
href="refD.html#debug">debug</a></code>, <code><a
href="refE.html#e">e</a></code>, <code><a href="ref_.html#^">^</a></code> and
<code><a href="refD.html#*Dbg">*Dbg</a></code>
<p>Other interrupts may be handled by <code><a
href="refA.html#alarm">alarm</a></code>, <code><a
href="refS.html#sigio">sigio</a></code>, <code><a
href="refH.html#*Hup">*Hup</a></code> and <code><a
href="refS.html#*Sig1">*Sig[12]</a></code>.
<p><hr>
<h3><a name="errors">Error Handling</a></h3>
<p>When a runtime error occurs, execution is stopped and an error handler is
entered.
<p>The error handler resets the I/O channels to the console, and displays the
location (if possible) and the reason of the error, followed by an error
message. That message is also stored in the global <code><a
href="refM.html#*Msg">*Msg</a></code>, and the location of the error in <code><a
href="ref_.html#^">^</a></code>. If the VAL of the global <code><a
href="refE.html#*Err">*Err</a></code> is non-<code>NIL</code> it is executed as
a <code>prg</code> body. If the standard input is from a terminal, a
read-eval-print loop (with a question mark "<code>?</code>" as prompt) is
entered (the loop is exited when an empty line is input). Then all pending
<code><a href="refF.html#finally">finally</a></code> expressions are executed,
all variable bindings restored, and all files closed. If the standard input is
not from a terminal, the interpreter terminates. Otherwise it is reset to its
top-level state.
<pre><code>
: (de foo (A B) (badFoo A B)) # 'foo' calls an undefined symbol
-> foo
: (foo 3 4) # Call 'foo'
!? (badFoo A B) # Error handler entered
badFoo -- Undefined
? A # Inspect 'A'
-> 3
? B # Inspect 'B'
-> 4
? # Empty line: Exit
:
</code></pre>
<p>Errors can be caught with <code><a href="refC.html#catch">catch</a></code>,
if a list of substrings of possible error messages is supplied for the first
argument. In such a case, the matching substring (or the whole error message if
the substring is <code>NIL</code>) is returned.
<p>An arbitrary error can be thrown explicitly with <code><a
href="refC.html#quit">quit</a></code>.
<p><hr>
<h3><a name="atres">@ Result</a></h3>
<p>In certain situations, the result of the last evaluation is stored in the VAL
of the symbol <code>@</code>. This can be very convenient, because it often
makes the assignment to temporary variables unnecessary.
<p>This happens in two - only superficially similar - situations:
<p><dl>
<dt><code><a href="refL.html#load">load</a></code>
<dd>In read-eval loops, the last three results which were printed at the console
are available in <code>@@@</code>, <code>@@</code> and <code>@</code>, in that
order (i.e the latest result is in <code>@</code>).
<pre><code>
: (+ 1 2 3)
-> 6
: (/ 128 4)
-> 32
: (- @ @@) # Subtract the last two results
-> 26
</code></pre>
<p><dt>Flow functions
<dd>Flow- and logic-functions store the result of their controlling expression -
respectively non-<code>NIL</code> results of their conditional expression - in
<code>@</code>.
<pre><code>
: (while (read) (println 'got: @))
abc # User input
got: abc # print result
123 # User input
got: 123 # print result
NIL
-> 123
: (setq L (1 2 3 4 5 1 2 3 4 5))
-> (1 2 3 4 5 1 2 3 4 5)
: (and (member 3 L) (member 3 (cdr @)) (set @ 999))
-> 999
: L
-> (1 2 3 4 5 1 2 999 4 5)
</code></pre>
<p>Functions with controlling expressions are
<a href="refC.html#case">case</a>,
<a href="refP.html#prog1">prog1</a>,
<a href="refP.html#prog2">prog2</a>,
and the bodies of <code><a href="refR.html#*Run">*Run</a></code> tasks.
<p>Functions with conditional expressions are
<a href="refA.html#and">and</a>,
<a href="refC.html#cond">cond</a>,
<a href="refD.html#do">do</a>,
<a href="refF.html#for">for</a>,
<a href="refI.html#if">if</a>,
<a href="refI.html#if2">if2</a>,
<a href="refI.html#ifn">ifn</a>,
<a href="refL.html#loop">loop</a>,
<a href="refN.html#nand">nand</a>,
<a href="refN.html#nond">nond</a>,
<a href="refN.html#nor">nor</a>,
<a href="refN.html#not">not</a>,
<a href="refO.html#or">or</a>,
<a href="refS.html#state">state</a>,
<a href="refU.html#unless">unless</a>,
<a href="refU.html#until">until</a>,
<a href="refW.html#when">when</a> and
<a href="refW.html#while">while</a>.
</dl>
<p><code>@</code> is generally local to functions and methods, its value is
automatically saved upon function entry and restored at exit.
<p><hr>
<h3><a name="cmp">Comparing</a></h3>
<p>In PicoLisp, it is legal to compare data items of arbitrary type. Any two
items are either
<p><dl>
<dt>Identical
<dd>They are the same memory object (pointer equality). For example, two
internal symbols with the same name are identical. In the 64-bit version, also
short numbers (up to 60 bits plus sign) are pointer-equal.
<dt>Equal
<dd>They are equal in every respect (structure equality), but need not to be
identical. Examples are numbers with the same value, transient symbols with the
same name or lists with equal elements.
<dt>Or they have a well-defined ordinal relationship
<dd>Numbers are comparable by their numeric value, strings by their name, and
lists recursively by their elements (if the CAR's are equal, their CDR's are
compared). For differing types, the following rule applies: Numbers are less
than symbols, and symbols are less than lists. As special cases,
<code>NIL</code> is always less than anything else, and <code>T</code> is always
greater than anything else.
</dl>
<p>To demonstrate this, <code><a href="refS.html#sort">sort</a></code> a list of
mixed data types:
<pre><code>
: (sort '("abc" T (d e f) NIL 123 DEF))
-> (NIL 123 DEF "abc" (d e f) T)
</code></pre>
<p>See also <code><a href="refM.html#max">max</a></code>, <code><a
href="refM.html#min">min</a></code>, <code><a
href="refR.html#rank">rank</a></code>, <code><a href="ref_.html#<"><</a></code>,
<code><a href="ref_.html#=">=</a></code>, <code><a
href="ref_.html#>">></a></code> etc.
<p><hr>
<h3><a name="oop">OO Concepts</a></h3>
<p>PicoLisp comes with built-in object oriented extensions. There seems to be a
common agreement upon three criteria for object orientation:
<p><dl>
<dt>Encapsulation
<dd>Code and data are encapsulated into <u>objects</u>, giving them both a
<u>behavior</u> and a <u>state</u>. Objects communicate by sending and receiving
<u>messages</u>.
<dt>Inheritance
<dd>Objects are organized into <u>classes</u>. The behavior of an object is
inherited from its class(es) and superclass(es).
<dt>Polymorphism
<dd>Objects of different classes may behave differently in response to the same
message. For that, classes may define different methods for each message.
</dl>
<p>PicoLisp implements both objects and classes with symbols. Object-local data
are stored in the symbol's property list, while the code (methods) and links to
the superclasses are stored in the symbol's VAL (encapsulation).
<p>In fact, there is no formal difference between objects and classes (except
that objects usually are anonymous symbols containing mostly local data, while
classes are named internal symbols with an emphasis on method definitions). At
any time, a class may be assigned its own local data (class variables), and any
object can receive individual method definitions in addition to (or overriding)
those inherited from its (super)classes.
<p>PicoLisp supports multiple inheritance. The VAL of each object is a (possibly
empty) association list of message symbols and method bodies, concatenated with
a list of classes. When a message is sent to an object, it is searched in the
object's own method list, and then (with a left-to-right depth-first search) in
the tree of its classes and superclasses. The first method found is executed and
the search stops. The search may be explicitly continued with the <code><a
href="refE.html#extra">extra</a></code> and <code><a
href="refS.html#super">super</a></code> functions.
<p>Thus, which method is actually executed when a message is sent to an object
depends on the classes that the object is currently linked to (polymorphism). As
the method search is fully dynamic (late binding), an object's type (i.e. its
classes and method definitions) can be changed even at runtime!
<p>While a method body is being executed, the global variable <code><a
href="refT.html#This">This</a></code> is set to the current object, allowing
the use of the short-cut property functions <code><a
href="ref_.html#=:">=:</a></code>, <code><a href="ref_.html#:">:</a></code>
and <code><a href="ref_.html#::">::</a></code>.
<p><hr>
<h3><a name="dbase">Database</a></h3>
<p>On the lowest level, a PicoLisp database is just a collection of <a
href="#external">external symbols</a>. They reside in a database file, and are
dynamically swapped in and out of memory. Only one database can be open at a
time (<code><a href="refP.html#pool">pool</a></code>).
<p>In addition, further external symbols can be specified to originate from
arbitrary sources via the <code><a href="refE.html#*Ext">*Ext</a></code>
mechanism.
<p>Whenever an external symbol's value or property list is accessed, it will be
automatically fetched into memory, and can then be used like any other symbol.
Modifications will be written to disk only when <code><a
href="refC.html#commit">commit</a></code> is called. Alternatively, all
modifications since the last call to <code>commit</code> can be discarded by
calling <code><a href="refR.html#rollback">rollback</a></code>.
<p><hr>
<h4><a name="trans">Transactions</a></h4>
<p>In the typical case there will be multiple processes operating on the same
database. These processes should be all children of the same parent process,
which takes care of synchronizing read/write operations and heap contents. Then
a database transaction is normally initiated by calling <code>(<a
href="refD.html#dbSync">dbSync</a>)</code>, and closed by calling <code>(<a
href="refC.html#commit">commit</a> 'upd)</code>. Short transactions, involving
only a single DB operation, are available in functions like <code><a
href="refN.html#new!">new!</a></code> and methods like <code><a
href="refE.html#entityMesssages">put!></a></code> (by convention with an
exclamation mark), which implicitly call <code>(dbSync)</code> and <code>(commit
'upd)</code> themselves.
<p>A transaction proceeds through five phases:
<p><ol>
<li><code><a href="refD.html#dbSync">dbSync</a></code> waits to get a <code><a
href="refL.html#lock">lock</a></code> on the root object <code><a
href="refD.html#*DB">*DB</a></code>. Other processes continue reading and
writing meanwhile.
<li><code><a href="refD.html#dbSync">dbSync</a></code> calls <code><a
href="refS.html#sync">sync</a></code> to synchronize with changes from other
processes. We hold the shared lock, but other processes may continue reading.
<li>We make modifications to the internal state of external symbols with
<code><a href="refE.html#entityMesssages">put>, set>, lose></a></code> etc. We -
and also other processes - can still read the DB.
<li>We call <code>(<a href="refC.html#commit">commit</a> 'upd)</code>.
<code>commit</code> obtains an exclusive lock (no more read operations by other
processes), writes an optional transaction log, and then all modified symbols.
As <code><a href="refU.html#upd">upd</a></code> is passed to 'commit', other
processes synchronize with these changes.
<li>Finally, all locks are released by 'commit'
</ol>
<p><hr>
<h4><a name="er">Entities / Relations</a></h4>
<p>The symbols in a database can be used to store arbitrary information
structures. In typical use, some symbols represent nodes of search trees, by
holding keys, values, and links to subtrees in their VAL's. Such a search tree
in the database is called <u>index</u>.
<p>For the most part, other symbols in the database are objects derived from the
<code><a href="refE.html#+Entity">+Entity</a></code> class.
<p>Entities depend on objects of the <code><a
href="refR.html#+relation">+relation</a></code> class hierarchy.
Relation-objects manage the property values of entities, they define the
application database model and are responsible for the integrity of mutual
object references and index trees.
<p>Relations are stored as properties in the entity classes, their methods are
invoked as daemons whenever property values in an entity are changed. When
defining an <code><a href="refE.html#+Entity">+Entity</a></code> class, relations are defined - in addition to
the method definitions of a normal class - with the <code><a
href="refR.html#rel">rel</a></code> function. Predefined relation classes
include
<p><ul>
<li>Primitive types like
<dl>
<dt><code><a href="refS.html#+Symbol">+Symbol</a></code>
<dd>Symbolic data
<dt><code><a href="refS.html#+String">+String</a></code>
<dd>Strings (just a general case of symbols)
<dt><code><a href="refN.html#+Number">+Number</a></code>
<dd>Integers and fixpoint numbers
<dt><code><a href="refD.html#+Date">+Date</a></code>
<dd>Calendar date values, represented by a number
<dt><code><a href="refT.html#+Time">+Time</a></code>
<dd>Time-of-the-day values, represented by a number
<dt><code><a href="refB.html#+Blob">+Blob</a></code>
<dd>"Binary large objects" stored in separate files
</dl>
<li>Object-to-object relations
<dl>
<dt><code><a href="refL.html#+Link">+Link</a></code>
<dd>A reference to some other entity
<dt><code><a href="refH.html#+Hook">+Hook</a></code>
<dd>A reference to an entity holding object-local index trees
<dt><code><a href="refJ.html#+Joint">+Joint</a></code>
<dd>A bi-directional reference to some other entity
</dl>
<li>Container prefix classes like
<dl>
<dt><code><a href="refL.html#+List">+List</a></code>
<dd>A list of any of the other primitive or object relation types
<dt><code><a href="refB.html#+Bag">+Bag</a></code>
<dd>A list containing a mixture of any of the other types
</dl>
<li>Index prefix classes
<dl>
<dt><code><a href="refR.html#+Ref">+Ref</a></code>
<dd>An index with other primitives or entities as key
<dt><code><a href="refK.html#+Key">+Key</a></code>
<dd>A unique index with other primitives or entities as key
<dt><code><a href="refI.html#+Idx">+Idx</a></code>
<dd>A full-text index, typically for strings
<dt><code><a href="refS.html#+Sn">+Sn</a></code>
<dd>Tolerant index, using a modified Soundex-Algorithm
</dl>
<li>Booleans
<dl>
<dt><code><a href="refB.html#+Bool">+Bool</a></code>
<dd><code>T</code> or <code>NIL</code>
</dl>
<li>And a catch-all class
<dl>
<dt><code><a href="refA.html#+Any">+Any</a></code>
<dd>Not specified, may be any of the above relations
</dl>
</ul>
<p><hr>
<h3><a name="pilog">Pilog (PicoLisp Prolog)</a></h3>
<p>A declarative language is built on top of PicoLisp, that has the semantics of
Prolog, but uses the syntax of Lisp.
<p>For an explanation of Prolog's declarative programming style, an introduction
like "Programming in Prolog" by Clocksin/Mellish (Springer-Verlag 1981) is
recommended.
<p>Facts and rules can be declared with the <code><a
href="refB.html#be">be</a></code> function. For example, a Prolog fact
'<code>likes(john,mary).</code>' is written in Pilog as:
<pre><code>
(be likes (John Mary))
</code></pre>
<p>and a rule '<code>likes(john,X) :- likes(X,wine), likes(X,food).</code>' is
in Pilog:
<pre><code>
(be likes (John @X) (likes @X wine) (likes @X food))
</code></pre>
<p>As in Prolog, the difference between facts and rules is that the latter ones
have conditions, and usually contain variables.
<p>A variable in Pilog is any symbol starting with an at-mark character
("<code>@</code>"). The symbol <code>@</code> itself can be used as an anonymous
variable: It will match during unification, but will not be bound to the matched
values.
<p>The <i>cut</i> operator of Prolog (usually written as an exclamation mark
(<code>!</code>)) is the symbol <code>T</code> in Pilog.
<p>An interactive query can be done with the <code><a
href="ref_.html#?">?</a></code> function:
<pre><code>
(? (likes John @X))
</code></pre>
<p>This will print all solutions, waiting for user input after each line. If a
non-empty line (not just a ENTER key, but for example a dot (<code>.</code>)
followed by ENTER) is typed, it will terminate.
<p>Pilog can be called from Lisp and vice versa:
<ul>
<li>The interface from Lisp is via the functions <code><a
href="refG.html#goal">goal</a></code> (prepare a query from Lisp data) and
<code><a href="refP.html#prove">prove</a></code> (return an association list of
successful bindings), and the application level functions <code><a
href="refP.html#pilog">pilog</a></code> and <code><a
href="refS.html#solve">solve</a></code>.
<li>When the CAR of a Pilog clause is a Pilog variable, the CDR is executed as a
Lisp expression and the result unified with that variable.
<li>Within such a Lisp expression in a Pilog clause, the current bindings of
Pilog variables can be accessed with the <code><a
href="ref_.html#->">-></a></code> function.
</ul>
<p><hr>
<h3><a name="conv">Naming Conventions</a></h3>
<p>It was necessary to introduce - and adhere to - a set of conventions for
PicoLisp symbol names. Because all (internal) symbols have a global scope (there
are no packages or name spaces), and each symbol can only have either a value or
function definition, it would otherwise be very easy to introduce name
conflicts. Besides this, source code readability is increased when the scope of
a symbol is indicated by its name.
<p>These conventions are not hard-coded into the language, but should be so into
the head of the programmer. Here are the most commonly used ones:
<p><ul>
<li>Global variables start with an asterisk "<code>*</code>"
<li>Functions and other global symbols start with a lower case letter
<li>Locally bound symbols start with an upper case letter
<li>Local functions start with an underscore "<code>_</code>"
<li>Classes start with a plus-sign "<code>+</code>", where the first letter
<ul>
<li>is in lower case for abstract classes
<li>and in upper case for normal classes
</ul>
<li>Methods end with a right arrow "<code>></code>"
<li>Class variables may be indicated by an upper case letter
</ul>
<p>For historical reasons, the global constant symbols <code>T</code> and
<code>NIL</code> do not obey these rules, and are written in upper case.
<p>For example, a local variable could easily overshadow a function definition:
<pre><code>
: (de max-speed (car)
(.. (get car 'speeds) ..) )
-> max-speed
</code></pre>
<p>Inside the body of <code>max-speed</code> (and all other functions called
during that execution) the kernel function <code>car</code> is redefined to some
other value, and will surely crash if something like <code>(car Lst)</code> is
executed. Instead, it is safe to write:
<pre><code>
: (de max-speed (Car) # 'Car' with upper case first letter
(.. (get Car 'speeds) ..) )
-> max-speed
</code></pre>
<p>Note that there are also some strict naming rules (as opposed to the
voluntary conventions) that are required by the corresponding kernel
functionalities, like:
<p><ul>
<li>Transient symbols are enclosed in double quotes (see <a
href="#transient-io">Transient Symbols</a>) <li>External symbols are enclosed in
braces (see <a href="#external-io">External Symbols</a>) <li>Pattern-Wildcards
start with an at-mark "<code>@</code>" (see <a href="refM.html#match">match</a>
and <a href="refF.html#fill">fill</a>) <li>Symbols referring to a shared library
contain a colon "<code>lib:sym</code>" </ul>
<p>With that, the last of the above conventions (local functions start with an
underscore) is not really necessary, because true local scope can be enforced
with transient symbols.
<p><hr>
<h3><a name="trad">Breaking Traditions</a></h3>
<p>PicoLisp does not try very hard to be compatible with traditional Lisp
systems. If you are used to some other Lisp dialects, you may notice the
following differences:
<p><dl>
<dt>Case Sensitivity
<dd>PicoLisp distinguishes between upper case and lower case characters in
symbol names. Thus, <code>CAR</code> and <code>car</code> are different symbols,
which was not the case in traditional Lisp systems.
<dt><code>QUOTE</code>
<dd>In traditional Lisp, the <code>QUOTE</code> function returns its
<i>first</i> unevaluated argument. In PicoLisp, on the other hand,
<code>quote</code> returns <i>all</i> (unevaluated) argument(s).
<dt><code>LAMBDA</code>
<dd>The <code>LAMBDA</code> function, in some way at the heart of traditional
Lisp, is completely missing (and <code>quote</code> is used instead).
<dt><code>PROG</code>
<dd>The <code>PROG</code> function of traditional Lisp, with its GOTO and ENTER
functionality, is also missing. PicoLisp's <code>prog</code> function is just a
simple sequencer (as <code>PROGN</code> in some Lisps).
<dt>Function/Value
<dd>In PicoLisp, a symbol cannot have a value <i>and</i> a function definition
at the same time. Though this is a disadvantage at first sight, it allows a
completely uniform handling of functional data.
</dl>
<p><hr>
<h3><a name="bugs">Bugs</a></h3>
<p>The names of the symbols <code>T</code> and <code>NIL</code> violate the <a
href="#conv">naming conventions</a>. They are global symbols, and should
therefore start with an asterisk "<code>*</code>". It is too easy to bind them
to some other value by mistake:
<pre><code>
(de foo (R S T)
...
</code></pre>
<p>However, <code><a href="refL.html#lint">lint</a></code> will issue a warning
in such a case.
<p><hr>
<h2><a name="fun">Function Reference</a></h2>
<p>This section provides a reference manual for the kernel functions, and some
extensions. See the thematically grouped list of indexes below.
<p>Though PicoLisp is a dynamically typed language (resolved at runtime, as
opposed to statically (compile-time) typed languages), many functions can only
accept and/or return a certain set of data types. For each function, the
expected argument types and return values are described with the following
abbreviations:
<p>The primary data types:
<p><ul>
<li><code>num</code> - Number
<li><code>sym</code> - Symbol
<li><code>lst</code> - List
</ul>
<p>Other (derived) data types
<p><ul>
<li><code>any</code> - Anything: Any primary data type
<li><code>flg</code> - Flag: Boolean value (<code>NIL</code> or non-<code>NIL</code>)
<li><code>cnt</code> - A count or a small number
<li><code>dat</code> - Date: Days, starting first of March of the year 0 A.D.
<li><code>tim</code> - Time: Seconds since midnight
<li><code>obj</code> - Object/Class: A symbol with methods and/or classes
<li><code>var</code> - Variable: Either a symbol or a cons pair
<li><code>exe</code> - Executable: A list as executable expression (<code>eval</code>)
<li><code>prg</code> - Prog-Body: A list of executable expressions (<code>run</code>)
<li><code>fun</code> - Function: Either a number (code-pointer), a symbol (message) or a list (lambda)
<li><code>msg</code> - Message: A symbol sent to an object (to invoke a method)
<li><code>cls</code> - Class: A symbol defined as an object's class
<li><code>typ</code> - Type: A list of <code>cls</code> symbols
<li><code>pat</code> - Pattern: A symbol whose name starts with an at-mark "<code>@</code>"
<li><code>pid</code> - Process ID: A number, the ID of a Unix process
<li><code>tree</code> - Database index tree specification
<li><code>hook</code> - Database hook object
</ul>
<p>
<a href="refA.html">A</a>
<a href="refB.html">B</a>
<a href="refC.html">C</a>
<a href="refD.html">D</a>
<a href="refE.html">E</a>
<a href="refF.html">F</a>
<a href="refG.html">G</a>
<a href="refH.html">H</a>
<a href="refI.html">I</a>
<a href="refJ.html">J</a>
<a href="refK.html">K</a>
<a href="refL.html">L</a>
<a href="refM.html">M</a>
<a href="refN.html">N</a>
<a href="refO.html">O</a>
<a href="refP.html">P</a>
<a href="refQ.html">Q</a>
<a href="refR.html">R</a>
<a href="refS.html">S</a>
<a href="refT.html">T</a>
<a href="refU.html">U</a>
<a href="refV.html">V</a>
<a href="refW.html">W</a>
<a href="refX.html">X</a>
<a href="refY.html">Y</a>
<a href="refZ.html">Z</a>
<a href="ref_.html">Other</a>
<p><dl>
<dt>Symbol Functions
<dd><code>
<a href="refN.html#new">new</a>
<a href="refS.html#sym">sym</a>
<a href="refS.html#str">str</a>
<a href="refC.html#char">char</a>
<a href="refN.html#name">name</a>
<a href="refS.html#sp?">sp?</a>
<a href="refP.html#pat?">pat?</a>
<a href="refF.html#fun?">fun?</a>
<a href="refA.html#all">all</a>
<a href="refS.html#symbols">symbols</a>
<a href="refL.html#local">local</a>
<a href="refI.html#import">import</a>
<a href="refI.html#intern">intern</a>
<a href="refE.html#extern">extern</a>
<a href="ref_.html#====">====</a>
<a href="refQ.html#qsym">qsym</a>
<a href="refL.html#loc">loc</a>
<a href="refB.html#box?">box?</a>
<a href="refS.html#str?">str?</a>
<a href="refE.html#ext?">ext?</a>
<a href="refT.html#touch">touch</a>
<a href="refZ.html#zap">zap</a>
<a href="refL.html#length">length</a>
<a href="refS.html#size">size</a>
<a href="refF.html#format">format</a>
<a href="refC.html#chop">chop</a>
<a href="refP.html#pack">pack</a>
<a href="refG.html#glue">glue</a>
<a href="refP.html#pad">pad</a>
<a href="refA.html#align">align</a>
<a href="refC.html#center">center</a>
<a href="refT.html#text">text</a>
<a href="refW.html#wrap">wrap</a>
<a href="refP.html#pre?">pre?</a>
<a href="refS.html#sub?">sub?</a>
<a href="refL.html#low?">low?</a>
<a href="refU.html#upp?">upp?</a>
<a href="refL.html#lowc">lowc</a>
<a href="refU.html#uppc">uppc</a>
<a href="refF.html#fold">fold</a>
<a href="refV.html#val">val</a>
<a href="refG.html#getd">getd</a>
<a href="refS.html#set">set</a>
<a href="refS.html#setq">setq</a>
<a href="refD.html#def">def</a>
<a href="refD.html#de">de</a>
<a href="refD.html#dm">dm</a>
<a href="refR.html#recur">recur</a>
<a href="refU.html#undef">undef</a>
<a href="refR.html#redef">redef</a>
<a href="refD.html#daemon">daemon</a>
<a href="refP.html#patch">patch</a>
<a href="refX.html#xchg">xchg</a>
<a href="refO.html#on">on</a>
<a href="refO.html#off">off</a>
<a href="refO.html#onOff">onOff</a>
<a href="refZ.html#zero">zero</a>
<a href="refO.html#one">one</a>
<a href="refD.html#default">default</a>
<a href="refE.html#expr">expr</a>
<a href="refS.html#subr">subr</a>
<a href="refL.html#let">let</a>
<a href="refL.html#let?">let?</a>
<a href="refU.html#use">use</a>
<a href="refA.html#accu">accu</a>
<a href="refP.html#push">push</a>
<a href="refP.html#push1">push1</a>
<a href="refP.html#pop">pop</a>
<a href="refC.html#cut">cut</a>
<a href="refD.html#del">del</a>
<a href="refQ.html#queue">queue</a>
<a href="refF.html#fifo">fifo</a>
<a href="refI.html#idx">idx</a>
<a href="refL.html#lup">lup</a>
<a href="refC.html#cache">cache</a>
<a href="refL.html#locale">locale</a>
<a href="refD.html#dirname">dirname</a>
</code>
<dt>Property Access
<dd><code>
<a href="refP.html#put">put</a>
<a href="refG.html#get">get</a>
<a href="refP.html#prop">prop</a>
<a href="ref_.html#;">;</a>
<a href="ref_.html#=:">=:</a>
<a href="ref_.html#:">:</a>
<a href="ref_.html#::">::</a>
<a href="refP.html#putl">putl</a>
<a href="refG.html#getl">getl</a>
<a href="refW.html#wipe">wipe</a>
<a href="refM.html#meta">meta</a>
</code>
<dt>Predicates
<dd><code>
<a href="refA.html#atom">atom</a>
<a href="refP.html#pair">pair</a>
<a href="refC.html#circ?">circ?</a>
<a href="refL.html#lst?">lst?</a>
<a href="refN.html#num?">num?</a>
<a href="refS.html#sym?">sym?</a>
<a href="refF.html#flg?">flg?</a>
<a href="refS.html#sp?">sp?</a>
<a href="refP.html#pat?">pat?</a>
<a href="refF.html#fun?">fun?</a>
<a href="refB.html#box?">box?</a>
<a href="refS.html#str?">str?</a>
<a href="refE.html#ext?">ext?</a>
<a href="refB.html#bool">bool</a>
<a href="refN.html#not">not</a>
<a href="ref_.html#==">==</a>
<a href="refN.html#n==">n==</a>
<a href="ref_.html#=">=</a>
<a href="ref_.html#<>"><></a>
<a href="ref_.html#=0">=0</a>
<a href="ref_.html#=T">=T</a>
<a href="refN.html#n0">n0</a>
<a href="refN.html#nT">nT</a>
<a href="ref_.html#<"><</a>
<a href="ref_.html#<="><=</a>
<a href="ref_.html#>">></a>
<a href="ref_.html#>=">>=</a>
<a href="refM.html#match">match</a>
</code>
<dt>Arithmetics
<dd><code>
<a href="ref_.html#+">+</a>
<a href="ref_.html#-">-</a>
<a href="ref_.html#*">*</a>
<a href="ref_.html#/">/</a>
<a href="ref_.html#%">%</a>
<a href="ref_.html#*/">*/</a>
<a href="ref_.html#**">**</a>
<a href="refI.html#inc">inc</a>
<a href="refD.html#dec">dec</a>
<a href="ref_.html#>>">>></a>
<a href="refL.html#lt0">lt0</a>
<a href="refL.html#le0">le0</a>
<a href="refG.html#ge0">ge0</a>
<a href="refG.html#gt0">gt0</a>
<a href="refA.html#abs">abs</a>
<a href="refB.html#bit?">bit?</a>
<a href="ref_.html#&">&</a>
<a href="ref_.html#|">|</a>
<a href="refX.html#x|">x|</a>
<a href="refS.html#sqrt">sqrt</a>
<a href="refS.html#seed">seed</a>
<a href="refR.html#rand">rand</a>
<a href="refM.html#max">max</a>
<a href="refM.html#min">min</a>
<a href="refL.html#length">length</a>
<a href="refS.html#size">size</a>
<a href="refA.html#accu">accu</a>
<a href="refF.html#format">format</a>
<a href="refP.html#pad">pad</a>
<a href="refM.html#money">money</a>
<a href="refR.html#round">round</a>
<a href="refB.html#bin">bin</a>
<a href="refO.html#oct">oct</a>
<a href="refH.html#hex">hex</a>
<a href="refH.html#hax">hax</a>
<a href="refF.html#fmt64">fmt64</a>
</code>
<dt>List Processing
<dd><code>
<a href="refC.html#car">car</a>
<a href="refC.html#cdr">cdr</a>
<a href="refC.html#caar">caar</a>
<a href="refC.html#cadr">cadr</a>
<a href="refC.html#cdar">cdar</a>
<a href="refC.html#cddr">cddr</a>
<a href="refC.html#caaar">caaar</a>
<a href="refC.html#caadr">caadr</a>
<a href="refC.html#cadar">cadar</a>
<a href="refC.html#caddr">caddr</a>
<a href="refC.html#cdaar">cdaar</a>
<a href="refC.html#cdadr">cdadr</a>
<a href="refC.html#cddar">cddar</a>
<a href="refC.html#cdddr">cdddr</a>
<a href="refC.html#cadddr">cadddr</a>
<a href="refC.html#cddddr">cddddr</a>
<a href="refN.html#nth">nth</a>
<a href="refC.html#con">con</a>
<a href="refC.html#cons">cons</a>
<a href="refC.html#conc">conc</a>
<a href="refC.html#circ">circ</a>
<a href="refR.html#rot">rot</a>
<a href="refL.html#list">list</a>
<a href="refN.html#need">need</a>
<a href="refR.html#range">range</a>
<a href="refF.html#full">full</a>
<a href="refM.html#make">make</a>
<a href="refM.html#made">made</a>
<a href="refC.html#chain">chain</a>
<a href="refL.html#link">link</a>
<a href="refY.html#yoke">yoke</a>
<a href="refC.html#copy">copy</a>
<a href="refM.html#mix">mix</a>
<a href="refA.html#append">append</a>
<a href="refD.html#delete">delete</a>
<a href="refD.html#delq">delq</a>
<a href="refR.html#replace">replace</a>
<a href="refI.html#insert">insert</a>
<a href="refR.html#remove">remove</a>
<a href="refP.html#place">place</a>
<a href="refS.html#strip">strip</a>
<a href="refS.html#split">split</a>
<a href="refR.html#reverse">reverse</a>
<a href="refF.html#flip">flip</a>
<a href="refT.html#trim">trim</a>
<a href="refC.html#clip">clip</a>
<a href="refH.html#head">head</a>
<a href="refT.html#tail">tail</a>
<a href="refS.html#stem">stem</a>
<a href="refF.html#fin">fin</a>
<a href="refL.html#last">last</a>
<a href="refM.html#member">member</a>
<a href="refM.html#memq">memq</a>
<a href="refM.html#mmeq">mmeq</a>
<a href="refS.html#sect">sect</a>
<a href="refD.html#diff">diff</a>
<a href="refI.html#index">index</a>
<a href="refO.html#offset">offset</a>
<a href="refP.html#prior">prior</a>
<a href="refA.html#assoc">assoc</a>
<a href="refA.html#asoq">asoq</a>
<a href="refR.html#rank">rank</a>
<a href="refS.html#sort">sort</a>
<a href="refU.html#uniq">uniq</a>
<a href="refG.html#group">group</a>
<a href="refL.html#length">length</a>
<a href="refS.html#size">size</a>
<a href="refV.html#val">val</a>
<a href="refS.html#set">set</a>
<a href="refX.html#xchg">xchg</a>
<a href="refP.html#push">push</a>
<a href="refP.html#push1">push1</a>
<a href="refP.html#pop">pop</a>
<a href="refC.html#cut">cut</a>
<a href="refQ.html#queue">queue</a>
<a href="refF.html#fifo">fifo</a>
<a href="refI.html#idx">idx</a>
<a href="refB.html#balance">balance</a>
<a href="refG.html#get">get</a>
<a href="refF.html#fill">fill</a>
<a href="refA.html#apply">apply</a>
</code>
<dt>Control Flow
<dd><code>
<a href="refL.html#load">load</a>
<a href="refA.html#args">args</a>
<a href="refN.html#next">next</a>
<a href="refA.html#arg">arg</a>
<a href="refR.html#rest">rest</a>
<a href="refP.html#pass">pass</a>
<a href="refQ.html#quote">quote</a>
<a href="refA.html#as">as</a>
<a href="refL.html#lit">lit</a>
<a href="refE.html#eval">eval</a>
<a href="refR.html#run">run</a>
<a href="refM.html#macro">macro</a>
<a href="refC.html#curry">curry</a>
<a href="refD.html#def">def</a>
<a href="refD.html#de">de</a>
<a href="refD.html#dm">dm</a>
<a href="refR.html#recur">recur</a>
<a href="refR.html#recurse">recurse</a>
<a href="refU.html#undef">undef</a>
<a href="refB.html#box">box</a>
<a href="refN.html#new">new</a>
<a href="refT.html#type">type</a>
<a href="refI.html#isa">isa</a>
<a href="refM.html#method">method</a>
<a href="refM.html#meth">meth</a>
<a href="refS.html#send">send</a>
<a href="refT.html#try">try</a>
<a href="refS.html#super">super</a>
<a href="refE.html#extra">extra</a>
<a href="refW.html#with">with</a>
<a href="refB.html#bind">bind</a>
<a href="refJ.html#job">job</a>
<a href="refL.html#let">let</a>
<a href="refL.html#let?">let?</a>
<a href="refU.html#use">use</a>
<a href="refA.html#and">and</a>
<a href="refO.html#or">or</a>
<a href="refN.html#nand">nand</a>
<a href="refN.html#nor">nor</a>
<a href="refX.html#xor">xor</a>
<a href="refB.html#bool">bool</a>
<a href="refN.html#not">not</a>
<a href="refN.html#nil">nil</a>
<a href="refT.html#t">t</a>
<a href="refP.html#prog">prog</a>
<a href="refP.html#prog1">prog1</a>
<a href="refP.html#prog2">prog2</a>
<a href="refI.html#if">if</a>
<a href="refI.html#if2">if2</a>
<a href="refI.html#ifn">ifn</a>
<a href="refW.html#when">when</a>
<a href="refU.html#unless">unless</a>
<a href="refC.html#cond">cond</a>
<a href="refN.html#nond">nond</a>
<a href="refC.html#case">case</a>
<a href="refS.html#state">state</a>
<a href="refW.html#while">while</a>
<a href="refU.html#until">until</a>
<a href="refL.html#loop">loop</a>
<a href="refD.html#do">do</a>
<a href="refA.html#at">at</a>
<a href="refF.html#for">for</a>
<a href="refC.html#catch">catch</a>
<a href="refT.html#throw">throw</a>
<a href="refF.html#finally">finally</a>
<a href="refC.html#co">co</a>
<a href="refY.html#yield">yield</a>
<a href="ref_.html#!">!</a>
<a href="refE.html#e">e</a>
<a href="ref_.html#$">$</a>
<a href="refS.html#sys">sys</a>
<a href="refC.html#call">call</a>
<a href="refT.html#tick">tick</a>
<a href="refI.html#ipid">ipid</a>
<a href="refO.html#opid">opid</a>
<a href="refK.html#kill">kill</a>
<a href="refQ.html#quit">quit</a>
<a href="refT.html#task">task</a>
<a href="refF.html#fork">fork</a>
<a href="refP.html#pipe">pipe</a>
<a href="refL.html#later">later</a>
<a href="refT.html#timeout">timeout</a>
<a href="refA.html#abort">abort</a>
<a href="refB.html#bye">bye</a>
</code>
<dt>Mapping
<dd><code>
<a href="refA.html#apply">apply</a>
<a href="refP.html#pass">pass</a>
<a href="refM.html#maps">maps</a>
<a href="refM.html#map">map</a>
<a href="refM.html#mapc">mapc</a>
<a href="refM.html#maplist">maplist</a>
<a href="refM.html#mapcar">mapcar</a>
<a href="refM.html#mapcon">mapcon</a>
<a href="refM.html#mapcan">mapcan</a>
<a href="refF.html#filter">filter</a>
<a href="refE.html#extract">extract</a>
<a href="refS.html#seek">seek</a>
<a href="refF.html#find">find</a>
<a href="refP.html#pick">pick</a>
<a href="refC.html#cnt">cnt</a>
<a href="refS.html#sum">sum</a>
<a href="refM.html#maxi">maxi</a>
<a href="refM.html#mini">mini</a>
<a href="refF.html#fish">fish</a>
<a href="refB.html#by">by</a>
</code>
<dt>Input/Output
<dd><code>
<a href="refP.html#path">path</a>
<a href="refI.html#in">in</a>
<a href="refO.html#out">out</a>
<a href="refE.html#err">err</a>
<a href="refC.html#ctl">ctl</a>
<a href="refI.html#ipid">ipid</a>
<a href="refO.html#opid">opid</a>
<a href="refP.html#pipe">pipe</a>
<a href="refA.html#any">any</a>
<a href="refS.html#sym">sym</a>
<a href="refS.html#str">str</a>
<a href="refL.html#load">load</a>
<a href="refH.html#hear">hear</a>
<a href="refT.html#tell">tell</a>
<a href="refK.html#key">key</a>
<a href="refP.html#poll">poll</a>
<a href="refP.html#peek">peek</a>
<a href="refC.html#char">char</a>
<a href="refS.html#skip">skip</a>
<a href="refE.html#eol">eol</a>
<a href="refE.html#eof">eof</a>
<a href="refF.html#from">from</a>
<a href="refT.html#till">till</a>
<a href="refL.html#line">line</a>
<a href="refF.html#format">format</a>
<a href="refS.html#scl">scl</a>
<a href="refR.html#read">read</a>
<a href="refP.html#print">print</a>
<a href="refP.html#println">println</a>
<a href="refP.html#printsp">printsp</a>
<a href="refP.html#prin">prin</a>
<a href="refP.html#prinl">prinl</a>
<a href="refM.html#msg">msg</a>
<a href="refS.html#space">space</a>
<a href="refB.html#beep">beep</a>
<a href="refT.html#tab">tab</a>
<a href="refF.html#flush">flush</a>
<a href="refR.html#rewind">rewind</a>
<a href="refR.html#rd">rd</a>
<a href="refP.html#pr">pr</a>
<a href="refW.html#wr">wr</a>
<a href="refW.html#wait">wait</a>
<a href="refS.html#sync">sync</a>
<a href="refE.html#echo">echo</a>
<a href="refI.html#info">info</a>
<a href="refF.html#file">file</a>
<a href="refD.html#dir">dir</a>
<a href="refL.html#lines">lines</a>
<a href="refO.html#open">open</a>
<a href="refC.html#close">close</a>
<a href="refP.html#port">port</a>
<a href="refL.html#listen">listen</a>
<a href="refA.html#accept">accept</a>
<a href="refH.html#host">host</a>
<a href="refC.html#connect">connect</a>
<a href="refU.html#udp">udp</a>
<a href="refS.html#script">script</a>
<a href="refO.html#once">once</a>
<a href="refR.html#rc">rc</a>
<a href="refA.html#acquire">acquire</a>
<a href="refR.html#release">release</a>
<a href="refP.html#pretty">pretty</a>
<a href="refP.html#pp">pp</a>
<a href="refS.html#show">show</a>
<a href="refV.html#view">view</a>
<a href="refH.html#here">here</a>
<a href="refP.html#prEval">prEval</a>
<a href="refM.html#mail">mail</a>
</code>
<dt>Object Orientation
<dd><code>
<a href="refC.html#*Class">*Class</a>
<a href="refC.html#class">class</a>
<a href="refD.html#dm">dm</a>
<a href="refR.html#rel">rel</a>
<a href="refV.html#var">var</a>
<a href="refV.html#var:">var:</a>
<a href="refN.html#new">new</a>
<a href="refT.html#type">type</a>
<a href="refI.html#isa">isa</a>
<a href="refM.html#method">method</a>
<a href="refM.html#meth">meth</a>
<a href="refS.html#send">send</a>
<a href="refT.html#try">try</a>
<a href="refO.html#object">object</a>
<a href="refE.html#extend">extend</a>
<a href="refS.html#super">super</a>
<a href="refE.html#extra">extra</a>
<a href="refW.html#with">with</a>
<a href="refT.html#This">This</a>
<a href="refC.html#can">can</a>
<a href="refD.html#dep">dep</a>
</code>
<dt>Database
<dd><code>
<a href="refP.html#pool">pool</a>
<a href="refJ.html#journal">journal</a>
<a href="refI.html#id">id</a>
<a href="refS.html#seq">seq</a>
<a href="refL.html#lieu">lieu</a>
<a href="refL.html#lock">lock</a>
<a href="refC.html#commit">commit</a>
<a href="refR.html#rollback">rollback</a>
<a href="refM.html#mark">mark</a>
<a href="refF.html#free">free</a>
<a href="refD.html#dbck">dbck</a>
<a href="refD.html#dbs">dbs</a>
<a href="refD.html#dbs+">dbs+</a>
<a href="refD.html#db:">db:</a>
<a href="refT.html#tree">tree</a>
<a href="refD.html#db">db</a>
<a href="refA.html#aux">aux</a>
<a href="refC.html#collect">collect</a>
<a href="refG.html#genKey">genKey</a>
<a href="refU.html#useKey">useKey</a>
<a href="refR.html#+relation">+relation</a>
<a href="refA.html#+Any">+Any</a>
<a href="refB.html#+Bag">+Bag</a>
<a href="refB.html#+Bool">+Bool</a>
<a href="refN.html#+Number">+Number</a>
<a href="refD.html#+Date">+Date</a>
<a href="refT.html#+Time">+Time</a>
<a href="refS.html#+Symbol">+Symbol</a>
<a href="refS.html#+String">+String</a>
<a href="refL.html#+Link">+Link</a>
<a href="refJ.html#+Joint">+Joint</a>
<a href="refB.html#+Blob">+Blob</a>
<a href="refH.html#+Hook">+Hook</a>
<a href="refI.html#+index">+index</a>
<a href="refK.html#+Key">+Key</a>
<a href="refR.html#+Ref">+Ref</a>
<a href="refR.html#+Ref2">+Ref2</a>
<a href="refI.html#+Idx">+Idx</a>
<a href="refS.html#+Sn">+Sn</a>
<a href="refF.html#+Fold">+Fold</a>
<a href="refA.html#+Aux">+Aux</a>
<a href="refU.html#+UB">+UB</a>
<a href="refD.html#+Dep">+Dep</a>
<a href="refL.html#+List">+List</a>
<a href="refN.html#+Need">+Need</a>
<a href="refM.html#+Mis">+Mis</a>
<a href="refA.html#+Alt">+Alt</a>
<a href="refB.html#blob">blob</a>
<a href="refD.html#dbSync">dbSync</a>
<a href="refN.html#new!">new!</a>
<a href="refS.html#set!">set!</a>
<a href="refP.html#put!">put!</a>
<a href="refI.html#inc!">inc!</a>
<a href="refB.html#blob!">blob!</a>
<a href="refU.html#upd">upd</a>
<a href="refR.html#rel">rel</a>
<a href="refR.html#request">request</a>
<a href="refO.html#obj">obj</a>
<a href="refF.html#fmt64">fmt64</a>
<a href="refR.html#root">root</a>
<a href="refF.html#fetch">fetch</a>
<a href="refS.html#store">store</a>
<a href="refC.html#count">count</a>
<a href="refL.html#leaf">leaf</a>
<a href="refM.html#minKey">minKey</a>
<a href="refM.html#maxKey">maxKey</a>
<a href="refI.html#init">init</a>
<a href="refS.html#step">step</a>
<a href="refS.html#scan">scan</a>
<a href="refI.html#iter">iter</a>
<a href="refP.html#prune">prune</a>
<a href="refZ.html#zapTree">zapTree</a>
<a href="refC.html#chkTree">chkTree</a>
<a href="refD.html#db/3">db/3</a>
<a href="refD.html#db/4">db/4</a>
<a href="refD.html#db/5">db/5</a>
<a href="refV.html#val/3">val/3</a>
<a href="refL.html#lst/3">lst/3</a>
<a href="refM.html#map/3">map/3</a>
<a href="refI.html#isa/2">isa/2</a>
<a href="refS.html#same/3">same/3</a>
<a href="refB.html#bool/3">bool/3</a>
<a href="refR.html#range/3">range/3</a>
<a href="refH.html#head/3">head/3</a>
<a href="refF.html#fold/3">fold/3</a>
<a href="refP.html#part/3">part/3</a>
<a href="refT.html#tolr/3">tolr/3</a>
<a href="refS.html#select/3">select/3</a>
<a href="refR.html#remote/2">remote/2</a>
</code>
<dt>Pilog
<dd><code>
<a href="refP.html#prove">prove</a>
<a href="ref_.html#->">-></a>
<a href="refU.html#unify">unify</a>
<a href="refB.html#be">be</a>
<a href="refC.html#clause">clause</a>
<a href="refR.html#repeat">repeat</a>
<a href="refA.html#asserta">asserta</a>
<a href="refA.html#assertz">assertz</a>
<a href="refR.html#retract">retract</a>
<a href="refR.html#rules">rules</a>
<a href="refG.html#goal">goal</a>
<a href="refF.html#fail">fail</a>
<a href="refP.html#pilog">pilog</a>
<a href="refS.html#solve">solve</a>
<a href="refQ.html#query">query</a>
<a href="ref_.html#?">?</a>
<a href="refR.html#repeat/0">repeat/0</a>
<a href="refF.html#fail/0">fail/0</a>
<a href="refT.html#true/0">true/0</a>
<a href="refN.html#not/1">not/1</a>
<a href="refC.html#call/1">call/1</a>
<a href="refO.html#or/2">or/2</a>
<a href="refN.html#nil/1">nil/1</a>
<a href="refE.html#equal/2">equal/2</a>
<a href="refD.html#different/2">different/2</a>
<a href="refA.html#append/3">append/3</a>
<a href="refM.html#member/2">member/2</a>
<a href="refD.html#delete/3">delete/3</a>
<a href="refP.html#permute/2">permute/2</a>
<a href="refU.html#uniq/2">uniq/2</a>
<a href="refA.html#asserta/1">asserta/1</a>
<a href="refA.html#assertz/1">assertz/1</a>
<a href="refR.html#retract/1">retract/1</a>
<a href="refC.html#clause/2">clause/2</a>
<a href="refS.html#show/1">show/1</a>
<a href="refD.html#db/3">db/3</a>
<a href="refD.html#db/4">db/4</a>
<a href="refD.html#db/5">db/5</a>
<a href="refV.html#val/3">val/3</a>
<a href="refL.html#lst/3">lst/3</a>
<a href="refM.html#map/3">map/3</a>
<a href="refI.html#isa/2">isa/2</a>
<a href="refS.html#same/3">same/3</a>
<a href="refB.html#bool/3">bool/3</a>
<a href="refR.html#range/3">range/3</a>
<a href="refH.html#head/3">head/3</a>
<a href="refF.html#fold/3">fold/3</a>
<a href="refP.html#part/3">part/3</a>
<a href="refT.html#tolr/3">tolr/3</a>
<a href="refS.html#select/3">select/3</a>
<a href="refR.html#remote/2">remote/2</a>
</code>
<dt>Debugging
<dd><code>
<a href="refP.html#pretty">pretty</a>
<a href="refP.html#pp">pp</a>
<a href="refS.html#show">show</a>
<a href="refL.html#loc">loc</a>
<a href="refD.html#*Dbg">*Dbg</a>
<a href="refD.html#doc">doc</a>
<a href="refM.html#more">more</a>
<a href="refD.html#depth">depth</a>
<a href="refW.html#what">what</a>
<a href="refW.html#who">who</a>
<a href="refC.html#can">can</a>
<a href="refD.html#dep">dep</a>
<a href="refD.html#debug">debug</a>
<a href="refD.html#d">d</a>
<a href="refU.html#unbug">unbug</a>
<a href="refU.html#u">u</a>
<a href="refV.html#vi">vi</a>
<a href="refL.html#ld">ld</a>
<a href="refT.html#trace">trace</a>
<a href="refU.html#untrace">untrace</a>
<a href="refT.html#traceAll">traceAll</a>
<a href="refP.html#proc">proc</a>
<a href="refH.html#hd">hd</a>
<a href="refB.html#bench">bench</a>
<a href="refE.html#edit">edit</a>
<a href="refL.html#lint">lint</a>
<a href="refL.html#lintAll">lintAll</a>
<a href="refS.html#select">select</a>
<a href="refU.html#update">update</a>
</code>
<dt>System Functions
<dd><code>
<a href="refC.html#cmd">cmd</a>
<a href="refA.html#argv">argv</a>
<a href="refO.html#opt">opt</a>
<a href="refV.html#version">version</a>
<a href="refG.html#gc">gc</a>
<a href="refR.html#raw">raw</a>
<a href="refA.html#alarm">alarm</a>
<a href="refP.html#protect">protect</a>
<a href="refH.html#heap">heap</a>
<a href="refS.html#stack">stack</a>
<a href="refA.html#adr">adr</a>
<a href="refE.html#env">env</a>
<a href="refU.html#up">up</a>
<a href="refD.html#date">date</a>
<a href="refT.html#time">time</a>
<a href="refU.html#usec">usec</a>
<a href="refS.html#stamp">stamp</a>
<a href="refD.html#dat$">dat$</a>
<a href="ref_.html#$dat">$dat</a>
<a href="refD.html#datSym">datSym</a>
<a href="refD.html#datStr">datStr</a>
<a href="refS.html#strDat">strDat</a>
<a href="refE.html#expDat">expDat</a>
<a href="refD.html#day">day</a>
<a href="refW.html#week">week</a>
<a href="refU.html#ultimo">ultimo</a>
<a href="refT.html#tim$">tim$</a>
<a href="ref_.html#$tim">$tim</a>
<a href="refT.html#telStr">telStr</a>
<a href="refE.html#expTel">expTel</a>
<a href="refL.html#locale">locale</a>
<a href="refA.html#allowed">allowed</a>
<a href="refA.html#allow">allow</a>
<a href="refP.html#pwd">pwd</a>
<a href="refC.html#cd">cd</a>
<a href="refC.html#chdir">chdir</a>
<a href="refC.html#ctty">ctty</a>
<a href="refI.html#info">info</a>
<a href="refD.html#dir">dir</a>
<a href="refD.html#dirname">dirname</a>
<a href="refE.html#errno">errno</a>
<a href="refN.html#native">native</a>
<a href="refC.html#call">call</a>
<a href="refT.html#tick">tick</a>
<a href="refK.html#kill">kill</a>
<a href="refQ.html#quit">quit</a>
<a href="refT.html#task">task</a>
<a href="refF.html#fork">fork</a>
<a href="refF.html#forked">forked</a>
<a href="refP.html#pipe">pipe</a>
<a href="refT.html#timeout">timeout</a>
<a href="refM.html#mail">mail</a>
<a href="refA.html#assert">assert</a>
<a href="refT.html#test">test</a>
<a href="refB.html#bye">bye</a>
</code>
<dt>Globals
<dd><code>
<a href="#nilSym">NIL</a>
<a href="refP.html#pico">pico</a>
<a href="refO.html#*OS">*OS</a>
<a href="refD.html#*DB">*DB</a>
<a href="refT.html#T">T</a>
<a href="refS.html#*Solo">*Solo</a>
<a href="refP.html#*PPid">*PPid</a>
<a href="refP.html#*Pid">*Pid</a>
<a href="ref_.html#@">@</a>
<a href="ref_.html#@@">@@</a>
<a href="ref_.html#@@@">@@@</a>
<a href="refT.html#This">This</a>
<a href="refP.html#*Prompt">*Prompt</a>
<a href="refD.html#*Dbg">*Dbg</a>
<a href="refZ.html#*Zap">*Zap</a>
<a href="refS.html#*Scl">*Scl</a>
<a href="refC.html#*Class">*Class</a>
<a href="refD.html#*Dbs">*Dbs</a>
<a href="refR.html#*Run">*Run</a>
<a href="refH.html#*Hup">*Hup</a>
<a href="refS.html#*Sig1">*Sig1</a>
<a href="refS.html#*Sig2">*Sig2</a>
<a href="ref_.html#^">^</a>
<a href="refE.html#*Err">*Err</a>
<a href="refM.html#*Msg">*Msg</a>
<a href="refU.html#*Uni">*Uni</a>
<a href="refL.html#*Led">*Led</a>
<a href="refT.html#*Tsm">*Tsm</a>
<a href="refA.html#*Adr">*Adr</a>
<a href="refA.html#*Allow">*Allow</a>
<a href="refF.html#*Fork">*Fork</a>
<a href="refB.html#*Bye">*Bye</a>
</code>
</dl>
<p><hr>
<h2><a name="down">Download</a></h2>
<p>The <code>PicoLisp</code> system can be downloaded from the <a
href="http://software-lab.de/down.html">PicoLisp Download</a> page.
</body>
</html>
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