Question

我需要一些帮助，我是Prolog的新手，我需要显示一个我初始化的变量，但是我一直都会遇到错误，任何人都可以帮助我吗？这是代码：

:- use_module(library(lists), [member/2]).
:- use_module(contestlib, [for/3]).

knights(N,Max) :-
    PlacedKnights = [],
    findall((X,Y),(for(X,1,N),for(Y,1,N)),Squares),
    knights(Squares,PlacedKnights,Max).

knights(N,Max,PlacedKnights) :- 
    findall((X,Y),(for(X,1,N),for(Y,1,N)),Squares),
    knights(Squares,PlacedKnights,Max).
knights([],PlacedKnights,Max) :-
    # length(PlacedKnights,Max).
knights([(X,Y)|Squares],PlacedKnights,Max) :-
    ( is_attacked(X,Y,PlacedKnights) ->
        knights(Squares,PlacedKnights,Max)
    ;
        knights(Squares,[knight(X,Y)|PlacedKnights],Max1),
        knights(Squares,PlacedKnights,Max2),
        Max is max(Max1,Max2)
    ).

is_attacked(X,Y,PlacedKnights) :-
    ( NX is X - 1, NY is Y - 2
    ; NX is X - 1, NY is Y + 2
    ; NX is X + 1, NY is Y - 2
    ; NX is X + 1, NY is Y + 2
    ; NX is X - 2, NY is Y - 1
    ; NX is X - 2, NY is Y + 1
    ; NX is X + 2, NY is Y - 1
    ; NX is X + 2, NY is Y + 1
    ),
    member(knight(NX,NY),PlacedKnights).

如果完成了knights子句，我需要在结尾处显示PlacedKnights 我试过这个，但我得到错误：

错误：=字符＆＃39;预期，发现1＆＃39;

 knights(N,Max,Display) :-
    PlacedKnights = [],
    findall((X,Y),(for(X,1,N),for(Y,1,N)),Squares),
    knights(Squares,PlacedKnights,Max), Display = PlacedKnights.

显示prolog变量

0 个答案: