Monkey & Banana in prolog

问题:

I have this prolog code for solving monkey and banana problem but my compiler give an error

This is my code:

move(state(middle, onbox, middle, hasnot), grasp,
     state(middle, onbox, middle, has)).
move(state(Pos, onfloor, Pos, Has), climb,
     state(Pos, onbox, Pos, Has)).
move(state(Pos1, onfloor, Pos1, Has), push(Pos1, Pos2),
     state(Pos2, onfloor, Pos2, Has)).
move(state(Pos1, onfloor, Box, Has), walk(Pos1, Pos2),
     state(Pos2, onfloor, Box, Has)).

canget(state(_,_,_,has)).
canget(State1) :- move(State1, Move, State2), canget(State2).

Error: Move is Singleton Variable.
What is my wrong?

回答1:

canget(S0) :-
   S = state(_,_,_,has),
   closure0(\X^Y^move(X,_,Y),S0,S).

Using closure0/3 and lambda