目标（指令）失败：用户：主 Prolog swi答案

【问题标题】：Goal (directive) failed: user:main Prolog swi目标（指令）失败：用户：主 Prolog swi
【发布时间】：2017-04-18 23:46:28
【问题描述】：

may(_,[],[]).
may(num(U),[est(C1,N1,NT1)|T1],[est(C1,N1,NT1)|T2]):-
   U =< NT1,
   may(num(U),T1,T2).

min(_,[],[]).
min(num(U),[est(C2,N2,NT2)|T3],[est(C2,N2,NT2)|T4]):-
    U > NT2,
    min(num(U),T3,T4).

main:-
   U is 2.0,
   mayores(num(U),
      [ est(3,"J",3.1), est(6,"P",4.5), est(7,"L",2.0), est(4,"R",1.5),
        est(2,"C",4.7), est(5,"F",2.0), est(9,"A",3.5), est(11,"K",4.8),
        est(8,"M",2.4), est(15,"S",1.5), est(17,"D",0.5), est(19,"G",2.0)
      ],
      T2), 
   menores(num(U),
      [ est(3,"J",3.1), est(6,"P",4.5), est(7,"L",2.0), est(4,"R",1.5),
        est(2,"C",4.7), est(5,"F",2.0), est(9,"A",3.5), est(11,"K",4.8),
        est(8,"M",2.4), est(15,"S",1.5), est(17,"D",0.5), est(19,"G",2.0)
      ],
      T4), 
   write(T4),
   write(T2),
   halt.
:- main.

代码需要将值 2 分成不同的列表。但是当我将它运行到ideone时它给了我这个错误。

Goal (directive) failed: user:main.

【问题讨论】：

你正在使用mayores和may ...

标签： prolog prolog-toplevel

【解决方案1】：

首先，在您的程序中，更喜欢使用顶层来代替halt/0 或write/1。因此：

t2_t4(T2, T4) :-
   Es = [ est(3,"J",3.1), est(6,"P",4.5), est(7,"L",2.0), est(4,"R",1.5),
          est(2,"C",4.7), est(5,"F",2.0), est(9,"A",3.5), est(11,"K",4.8),
          est(8,"M",2.4), est(15,"S",1.5), est(17,"D",0.5), est(19,"G",2.0)
      ],
   U is 2.0,
   mayores(num(U), Es, T2), 
   menores(num(U), Es, T4).

?- t2_t4(T2, T4).
false.

不幸的是，这失败了。为了减少失败的根源，减少数据的大小和目标的数量。我完成于：

:- op(950, fy, *)。 *(_)。月经（_，[]，_/*[]*/）。 menores(num(U), [est(C2,N2,NT2)|T3], _/*~~[est(C2,N2,NT2)|T4]~~*/):- U > NT2, * ~~menores(num(U),T3,T4)~~。 t2_t4（T2，T4）：- Es = [ /* ~~est(3,"J",3.1), est(6,"P",4.5), est(7,"L",2.0), est(4,"R",1.5 ),~~ ~~est(2,"C",4.7), est(5,"F",2.0), est(9,"A",3.5), est(11,"K",4.8),~~ ~~est(8,"M",2.4), est(15,"S",1.5), est(17,"D",0.5),~~ */ 估计（19，“G”，2.0） ], U 为 2.0， * ~~mayores(num(U), Es, T2)~~, 月经（num（U），Es，T4）。

所以实际的问题是menores 仅针对元素较小的情况定义。如果它们相等或更大，menores 将失败。您也需要明确说明这一点。 mayores 的参数相同。为什么不将两者放在一个谓词中？另外，不用num/1。

mayores_menores(_,[], [], []).
mayores_menores(U,[E|Es],[E|Mays],Mens):-
   E = est(_,_,NT),
   U =< NT,
   mayores_menores(U,Es,Mays,Mens).
mayores_menores(U,[E|Es],Mays,[E|Mens]):-
   E = est(_,_,NT),
   U > NT,
   mayores_menores(U,Es,Mays,Mens).


t2_t4x(T2, T4) :-
   Es = [ est(3,"J",3.1), est(6,"P",4.5), est(7,"L",2.0), est(4,"R",1.5),
          est(2,"C",4.7), est(5,"F",2.0), est(9,"A",3.5), est(11,"K",4.8),
          est(8,"M",2.4), est(15,"S",1.5), est(17,"D",0.5), est(19,"G",2.0)
      ],
   mayores_menores(2.0, Es, T2, T4).

【讨论】：