The Prolog Library

The Prolog library comprises a number of packages which are thought to be useful in a number of applications. Note that the predicates in the Prolog library are not built-in predicates. One has to explicitly load each package to get access to its predicates. The following packages are provided:

arrays

provides an implementation of extendible arrays with logarithmic access time.

assoc

uses AVL trees to implement "association lists", i.e. extendible finite mappings from terms to terms.

atts

provides a means of associating with variables arbitrary attributes, i.e. named properties that can be used as storage locations as well as hooks into Prolog's unification.

heaps

implements binary heaps, the main application of which are priority queues.

lists

provides basic operations on lists.

terms

provides a number of operations on terms.

ordsets

defines operations on sets represented as lists with the elements ordered in Prolog standard order.

queues

defines operations on queues (FIFO stores of information).

random

provides a random number generator.

system

provides access to operating system services.

trees

uses binary trees to represent non-extendible arrays with logarithmic access time. The functionality is very similar to that of library(arrays), but library(trees) is slightly more efficient if the array does not need to be extendible.

ugraphs

provides an implementation of directed and undirected graphs with unlabeled edges.

wgraphs

provides an implementation of directed and undirected graphs where each edge has an integral weight.

sockets

provides an interface to system calls for manipulating sockets.

linda/client

linda/server

provides an implementation of the Linda concept for process communication.

db

provides storage and retrieval of terms on disk files with user-defined multiple indexing.

clpb

provides constraint solving over Booleans.

clpq

clpr

provides constraint solving over Q (Rationals) or R (Reals).

clpfd

provides constraint solving over Finite (Integer) Domains

chr

provides Constraint Handling Rules

objects

provides the combination of the logic programming and the object-oriented programming paradigms.

gcla

is a specification tool that is based on Generalized Horn Clause Language, a generalization of Prolog.

tcltk

An interface to the Tcl/Tk language and toolkit.

gauge

is a profiling tool for Prolog programs with a graphical interface based on tcltk.

charsio

defines I/O predicates that read from, or write to, a list of character codes.

jasper

An interface to the Java language.

flinkage

is a utility program for generating glue code for the Foreign Language Interface when building statically linked Runtime Systems or Development Systems.

timeout

provides a way of running goals with an execution time limit.

xref

provides a cross reference producer for debugging and program analysis.

To load a library package Package, you will normally enter a query

| ?- use_module(library(Package)).

A library package normally consists of one or more hidden modules.

An alternative way of loading from the library is using the built-in predicate require/1 (see section Reading-in Programs). The index file `INDEX.pl' needed by require/1 can be created by the make_index program. This program is loaded as:

| ?- use_module(library(mkindex)).

make_index:make_library_index(+LibraryDirectory)

Creates a file `INDEX.pl' in LibraryDirectory. All `*.pl' files in the directory and all its subdirectories are scanned for module/2 declarations. From these declarations, the exported predicates are entered into the index.

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