如何在Prolog中使用评估

Question

I am very new to Prolog and I can't seem to wrap my mind around it. I am trying to write a predicate that, given facts predefined about prerequisites for college, will be able to list all the prereqs in a list.

So far I have

list_prereqs(Course, List) :-
   prereqs(Course, List),
   list_prereqs(List, A).

But this doesn't work. How do I use the answer that I get from prereqs in the recursive call? Or am I going about this all wrong?

Answer 1

How about findall/3 ? Like this;

list_prereqs(Prereqs) :-
   findall(prereqs(Course, List), prereqs(Course, List), Prereqs).

Prereqs above is unified to the list of all the prereqs.