猴子＆amp;香蕉在prolog

Question

我有解决猴子和香蕉问题的prolog代码，但我的编译器发出错误

这是我的代码：

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).

错误：Move是Singleton Variable 我错了什么？

Answer 1

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

使用closure0/3和lambda