%/* Monkey and the banana problem                       Robert Klerer  */
% solve(Time, Actions, States)? Generates possible plans...
solve(0,[],[state(a,c,d,couch,nil)]).
solve(T1,[A; H],[X,Y; Z]) :-
        solve(T0,H,[Y; Z]) , 
        rule(A,Y,X) , 
        not member(X,[Y; Z]) , 
        T1 is T0+1.

rule(get_off(couch),state(a,W,X,couch,Y),state(a,W,X,floor,Y)).
rule(get_off(chair),state(W,W,X,chair,Y),state(W,W,X,floor,Y)).
rule(get_on(chair),state(W,W,X,floor,Y),state(W,W,X,chair,Y)).
rule(get_on(couch),state(a,W,X,floor,Y),state(a,W,X,couch,Y)).

rule(move(self,a),state(W,X,Y,floor,nil),state(a,X,Y,floor,nil)).
rule(move(self,b),state(W,X,Y,floor,nil),state(b,X,Y,floor,nil)).
rule(move(self,c),state(W,X,Y,floor,nil),state(c,X,Y,floor,nil)).
rule(move(self,d),state(W,X,Y,floor,nil),state(d,X,Y,floor,nil)).

rule(move(stick,a),state(W,X,W,floor,stick),state(a,X,a,floor,stick)).
rule(move(stick,b),state(W,X,W,floor,stick),state(b,X,b,floor,stick)).
rule(move(stick,c),state(W,X,W,floor,stick),state(c,X,c,floor,stick)).
rule(move(stick,d),state(W,X,W,floor,stick),state(d,X,d,floor,stick)).

rule(move(chair,a),state(W,W,X,floor,nil),state(a,a,X,floor,nil)).
rule(move(chair,b),state(W,W,X,floor,nil),state(b,b,X,floor,nil)).
rule(move(chair,c),state(W,W,X,floor,nil),state(c,c,X,floor,nil)).
rule(move(chair,d),state(W,W,X,floor,nil),state(d,d,X,floor,nil)).

rule(grasp(stick),state(W,X,W,floor,nil),state(W,X,W,floor,stick)).
rule(drop(stick),state(W,X,W,floor,stick),state(W,X,W,floor,nil)).

rule(grasp(banana),state(b,X,Y,chair,stick),state(b,X,Y,chair,banana)).


:- write('Monkey and banana loaded!'), nl.
:-listing.