NAME

Prolog Interpreter alpha 0.02

SYNOPSIS

        Language::Prolog::Interpreter->readFile('E:/src/PROLOG/flamenco.pr');

or

        $a = <<'EOPROLOG';
        parent(john,sally).
        parent(john,joe).
        parent(mary,joe).
        parent(phil,beau).
        parent(jane,john).
        grandparent(X,Z) :-parent(X,Y),parent(Y,Z).
        EOPROLOG
        ;
        while ($a) {
                eval 'Language::Prolog::Interpreter->readStatement(\$a)';
                $@ && die $@,$a,"\n";
                $a=~s/^\s*//;
        }

        # Above is same as
        # eval 'Language::Prolog::Interpreter->readFile($pathtomyfile)';

        $a = '?- grandparent(GPARENT,GCHILD).';
        print $a,"\n";
        $Q = Language::Prolog::Interpreter->readStatement(\$a);
        while($Q->query()) {
                print "found solutions\n";
                print 'GPARENT = ',$Q->variableResult('GPARENT'),"\n";
                print 'GCHILD = ',$Q->variableResult('GCHILD'),"\n\n";
        }
        print "no more solutions\n\n";

        $a = 'member(A,[A|_]).';
        $b = 'member(A,[_|B]) :- member(A,B).'; #Classic member
        Language::Prolog::Interpreter->readStatement(\$a);
        Language::Prolog::Interpreter->readStatement(\$b);

        $a = '?- member(c(V),[a(a),b(b),c(c),d(d),c(q)]).';
        print $a,"\n";
        $Q = Language::Prolog::Interpreter->readStatement(\$a);
        while($Q->query()) {
                print "found solutions\n";
                print 'V = ',$Q->variableResult('V'),"\n\n";
        }
        print "no more solutions\n\n";

DESCRIPTION

A simple interpreter which doesn't allow infix operators (except for :- and ,, both of which are built in).

SYNTAX

There are three possible statements:

1. Clauses

A single clause ending in a statement terminator (.).

This gets added to the database.

2. Rules

A single rule ending in a statement terminator (.).

This gets added to the store.

3. Queries

The he query characters ?-, followed by a comma separated list of clauses, ending in a statement terminator (.).

This creates and returns a query.

Comments

Multi-line comments are Java-like, taking the form /** ... **/.

Single-line/end-of-line comments are donnated by %.

Whitespace

Whitespace is ignored everywhere except in single quoted atoms

TERMS

Terms are:-

Lists1:

Comma separated lists of terms enclosed in square brackets

        e.g [Term1,Term2]

Lists2:

As List1, but final term is a variable separated by a '|'

        e.g [Term1,Term2|Variable]

Atoms1:

sequence of characters/digits/underscore (i.e \w character class) starting with a lower case character.

        e.g. this_Is_An_Atom

Atoms1:

any sequence of characters enclosed in single quotes (')

        e.g. 'This is another atom!'

Variables:

sequence of characters/digits/underscore (i.e \w character class) starting with an upper case character or underscore

        e.g. This_is_a_var, _and_this, _90

Clauses:

an Atom1 immediately followed by a left bracket, (, followed by a comma separated list of terms, terminating in a right bracket.

        e.g clause(one), clause2(a,hello,'More !',[a,b,c])

Rules:

A Clause, followed by optional whitespace, followed by :-, followed by optional whitespace, followed by a list of clauses separated by commas.

AUTHOR

Jack Shirazi.

Since Mr Shirzai seems to have vanished, updated by Lee Goddard <lgoddard@cpan.org> to support file parsing, single- and multi-line comments, and multi-ilne clauses.

COPYRIGHT

Copyright (C) 1995, Jack Shirazi. All Rights Reserved.

Updates Copyright (C) 2001, Lee Goddard. All Rights Reserved.

Usage is under the same terms as for Perl itself.