我有这段代码
DOMAINS
s = symbol.
sList = symbol*.
PREDICATES
nondeterm link(s, s,integer).
nondeterm depth_first_search(s, s, sList,integer).
CLAUSES
link("Erbil","Koysinjaq",12).
link("Erbil","Kirkuk",15).
link("Erbil","Shaqlawa",15).
link("Erbil","Mosul",22).
link("Shaqlawa","Akre",33).
link("Mosul","Duhok",44).
link("Mosul","Akre",55).
link("Kirkuk","Koysinjaq",66).
link("Kirkuk","Chamchamal",88).
link("Chamchamal","Sulaimani",34).
link("Koysinjaq","Sulaimani",22).
link("Sulaimani","Ranya",33).
link("Akre","Duhok",22).
depth_first_search(X, X, [X],0).
depth_first_search(X, Y, [X|T],L):-
link(X, Z , L1),
depth_first_search(Z, Y, T,L2),L=L1+L2 .
GOAL
depth_first_search("Erbil", "Duhok", PathToGoal,Dis).
我想找到最短的路径和两个城市之间的距离,我从开始节点的目标开始,计算距离,然后返回它,但是当我运行它时我得到了错误PROGRAM ERROR 1040
什么都不知道,所以在谷歌搜索,没有什么是可以理解的