#!/usr/local/bin/perl -l

use strict;
use warnings;
use lib '../lib/';
use aliased 'AI::Prolog::Parser';
use aliased 'AI::Prolog::Term';
use aliased 'AI::Prolog::Engine';

my $parser = Parser->new("append([a],[b,c,d],Z).");
my $query  = Term->new($parser);
my $engine = Engine->new($query,Parser->consult(append_prog()));

print "Appending two lists 'append([a],[b,c,d],Z).'";
print $engine->run;
while (my $result = $engine->more) {
    print $result;
}

$parser = Parser->new("append(X,[b,c,d],[a,b,c,d]).");
$query  = Term->new($parser);
$engine = Engine->new($query,Parser->consult(append_prog()));

print "\nWhich lists appends to a known list to form another known list 'append(X,[b,c,d],[a,b,c,d]).'";
print $engine->run;
while (my $result = $engine->more) {
    print $result;
}

$parser = Parser->new("append(X,Y,[a,b,c,d]).");
$query  = Term->new($parser);
$engine = Engine->new($query,Parser->consult(append_prog()));

print "\nWhich lists append to form a known list 'append(X,Y,[a,b,c,d]).'";
print $engine->run;
while (my $result = $engine->more) {
    print $result;

}

sub append_prog {
    "append([], X, X)."
   ."append([W|X],Y,[W|Z]) :- append(X,Y,Z).";
}