想打印路径，但出现错误

Question

  domains
  list=symbol*
  predicates
     path(symbol,symbol)
     solve(symbol,symbol,list)
     insert(symbol,list,list)
  clauses
  path(a,b). 
  path(b,c).
  path(c,d).
  path(d,e). 
  path(a,d).
  path(c,e).
solve(X, Z, P):-
    path(X,Z),
insert(Z,Temp,P),
P=Temp.
solve(X,Z,P):-
path(X,Y),
insert(Y,Temp,P),
P=Temp,
    solve(Y,Z,P).
insert(X,[X|Tail],Tail).
insert(X,[Y|Tail],[Y|Tail1]):-
insert(X,Tail,Tail1).

想打印我从一个点到另一个点所遵循的路径。但是会出现错误。例如，我想:

goal
solve(a,c,P).

答:p = (a, b, c)

Answer 1

我不明白你的解谓词是做什么的。以下是我的猜测:

solve(Start, End, [Start|PathMinusStart]) :-
    solve_(Start, End, PathMinusStart).
solve_(Start, End, [End]) :-
    path(Start, End).
solve_(Start, End, [Waypoint|Path]) :-
    path(Start, Waypoint),
    solve_(Waypoint, End, Path).

solve将使用;为您提供一个接一个的路径来浏览它们(好吧，我想至少因为我对您正在使用的prolog实现一无所知)。

Answer 2

search_path(Node, End, Temp, Path) :- path(Node,End),reverse([End | [Node | Temp]], Path).
search_path(Node, End, Temp, Path) :- 
  path(Node, Next),
  not(member(Node, Temp)),
  search_path(Next, End, [Node | Temp], Path).
solve(Start, End, Path) :- search_path(Start, End, [], Path).