试图学习Prolog，无法弄清楚出了什么问题

Question

做一个小示例，我想在某个pozition

的列表中插入一个符号

domains
    element = symbol
    list = element*
    position = integer
predicates
    insert (element, position, list, list) %(input,input,input,output)
clauses 
    insert (E,_,[],[E]). 
    insert (E, 1,[H|T],[E|[H|T]]).       %(I insert E on the "first" position)
    % I get errors how E and T are not bound. I have no idea how to make them bound
    insert (E,P,[H|T],[H1|T1]) :-
           P > 1,
           P1 = P - 1,
           insert (E,P1,T,T1).

它行不通...但是我不知道为什么。好吧，有点有效。我希望它向我展示outputList = [NEW_LIST]，而不是显示每个symbolName=_，然后显示outputList = [_,_,_,_]。

Answer 1

显然，符号数据类型存在一些问题，如果我使用整数，它会自行修复。

另外，这是

domains
    element = integer
     list = element*
     position = integer
predicates
     insert (element, position, list, list) %(input,input,input,output)
clauses 
     insert (E,_,[],[E]). 
     insert (E, 1,[H|T],[E|[H|T]]).
     insert (E,P,[H|T],[H|T1]) :-  % has to be "H" (or anything else) in both
          P > 1,                   % so prolog understands what we are trying to do
          P1 = P - 1,              % don't really understand why though
          insert (E,P1,T,T1).      % I might be wrong