Prolog - get the factors for a given number doesn't stop?

Question

I need to find the factors of a given number , e.g :

?- divisors2(40,R).
R = [40,20,10,8,5,4,2,1].

The code :

% get all t         


        

Answer 1

You have a bug here

divisors1([H|T],S,X):-
   divisors1(T,W,X),
   Z is X mod H,
   Z==0,S=[H|W]. <=== here

If Z is Zero then S = [H|W] else S = W.