我正在学习 Prolog，但我遇到了这个问题，我真的不知道如何完成它。我认为我的代码是正确的，但我在 Sictus 中不断收到警告，我不知道我的错误在哪里。
这是问题所在：
/*
File: fall_dance_competition.pl
Purpose: Solve the Fall "Dance Competition" puzzle
Notes:
Saturday night, four couples went to the town’s annual fall dance
competition. Each couple dressed in matching colors and they all
performed very well. The competition was fierce but friendly and
everyone had a grand time. Determine the name of each couple,
their place in the competition, and the color each couple wore.
1. Tom, who wasn’t married to Jean, placed better than Mary
and her husband but worse than the West couple did.
2. The couple wearing brown won the event. Mr. and Mrs.
King came in 4th place.
3. Bill Snow and his wife didn’t wear the green outfits.
Jean wasn’t married to John.
4. The couple wearing blue placed after the couple wearing red
but before the King couple.
5. From 4th place to 1st place, the couples won in the following
order: John and his wife, the
couple wearing blue, Mr. and Mrs. Forest, Brenda and her husband.
6. George and his wife placed better than Tom and Sara.
*/
这是我的代码：
use_module( library(basics)).use_module(library(lists)).
lista([pareja(_,_,_,_,_),pareja(_,_,_,_,_),
pareja(_,_,_,_,_),pareja(_,_,_,_,_)]).
constraints( S ) :-
member(pareja(tom, _, _, _, _), S)
member(pareja(_, jean, _, _, _), S)
member(pareja(_, mary, _, _, _), S)
member(pareja(_, _, west, _, _), S)
perm2(Left_1, Right_1, pareja(tom, _, _, _, _), pareja(_, mary, _, _, _))
nextto(Left_1, Right_1, S)
perm2(Left_2, Right_2, pareja(_, _, west, _, _), pareja(tom, _, _, _, _))
nextto(Left_2, Right_2, S)
S = [pareja(_, _, _, 1, brown), _, _, _]
S = [_, _, _, pareja(_, _, king, 4, _)]
member(pareja(bill, _, snow, _, _), S)
member(pareja(_, _, _, _, green), S)
member(pareja(john, _, _, _, _), S)
nextto(pareja(_, _, _, _, red), pareja(_, _, _, _, blue), S)
nextto(pareja(_, _, _, _, blue), pareja(_, _, king, _, _), S)
S = [_, _, _, pareja(john, _, _, 4, _)]
S = [_, _, pareja(_, _, _, 3, blue), _]
S = [_, pareja(_, _, forest, 2, _), _, _]
S = [pareja(_, brenda, _, 1, _), _, _, _]
member(pareja(george, _, _, _, _), S)
member(pareja(tom, sara, _, _, _), S)
nextto(pareja(george, _, _, _, _), pareja(tom, sara, _, _, _), S).
green( Who ) :-
lista(S),
constraints(S),
member(pareja(_, Who, _, _, green), S).
nextto(X, Y, List) :- append(_, [X,Y|_], List).
append([X|Y],Z,[X|W]) :- append(Y,Z,W).
append([],X,X).
member(X,[X|T]).
member(X,[H|T]) :- member(X,T).
perm2(X,Y, X,Y).
perm2(X,Y, Y,X).
我使用了一些斑马拼图的例子来做到这一点。