#!/usr/local/bin/perl
# see http://www.compapp.dcu.ie/~alex/LOGIC/monkey.html
# This is the classic Monkey/Banana problem
use strict;
use warnings;
use lib ('../lib/', 'lib');
use AI::Prolog;
my $prolog = AI::Prolog->new(<<'END_PROLOG');
perform(grasp,
state(middle, middle, onbox, hasnot),
state(middle, middle, onbox, has)).
perform(climb,
state(MP, BP, onfloor, H),
state(MP, BP, onbox, H)).
perform(push(P1,P2),
state(P1, P1, onfloor, H),
state(P2, P2, onfloor, H)).
perform(walk(P1,P2),
state(P1, BP, onfloor, H),
state(P2, BP, onfloor, H)).
getfood(state(_,_,_,has)).
getfood(S1) :- perform(Act, S1, S2),
nl, print('In '), print(S1), print(' try '), print(Act), nl,
getfood(S2).
END_PROLOG
$prolog->query("getfood(state(atdoor,atwindow,onfloor,hasnot)).");
$prolog->results; # note that everything is done internally.
# there's no need to process the results