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.