PROLOG
:- reconsult('prolog adts').
plan(State, Goal, _, Moves) :- equal_set(State, Goal),
write('moves are'), nl,
reverse_print_stack(Moves).
plan(State, Goal, Been_list, Moves) :-
move(Name, Preconditions, Actions),
conditions_met(Preconditions, State),
change_state(State, Actions, Child_state),
not(member_state(Child_state, Been_list)),
stack(Child_state, Been_list, New_been_list),
stack(Name, Moves, New_moves),
plan(Child_state, Goal, New_been_list, New_moves),!.
change_state(S, [], S).
change_state(S, [add(P)|T], S_new) :- change_state(S, T, S2),
add_to_set(P, S2, S_new), !.
change_state(S, [del(P)|T], S_new) :- change_state(S, T, S2),
remove_from_set(P, S2, S_new), !.
conditions_met(P, S) :- subset(P, S).
member_state(S, [H|_]) :- equal_set(S, H).
member_state(S, [_|T]) :- member_state(S, T).
reverse_print_stack(S) :- empty_stack(S).
reverse_print_stack(S) :- stack(E, Rest, S),
reverse_print_stack(Rest),
write(E), nl.
/* sample moves */
move(pickup(X), [handempty, clear(X), on(X, Y)],
[del(handempty), del(clear(X)), del(on(X, Y)),
add(clear(Y)), add(holding(X))]).
move(pickup(X), [handempty, clear(X), ontable(X)],
[del(handempty), del(clear(X)), del(ontable(X)),
add(holding(X))]).
move(putdown(X), [holding(X)],
[del(holding(X)), add(ontable(X)), add(clear(X)),
add(handempty)]).
move(stack(X, Y), [holding(X), clear(Y)],
[del(holding(X)), del(clear(Y)), add(handempty), add(on(X, Y)),
add(clear(X))]).
go(S, G) :- plan(S, G, [S], []).
test :- go([handempty, ontable(b), ontable(c), on(a, b), clear(c), clear(a)],
[handempty, ontable(c), on(a,b), on(b, c), clear(a)]).
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