Question

Learning this very slowly… got some books today and they just plain suck..

so.. I’m trying to move X position through a list.. then return the remainder of the list. Problem being I’m returning merely the element at that position rather than the list. I believe my problem is either the base case or the unknown variable. I’m also not 100% sure when the “_” should be used..

an explanation would be extremely helpful.. thanx in advance.

move([X|_],0,X).
move([X|XS],K,L) :- K>0,
    K1 is K-1, move(XS,K1,L).

Answer 1

The base case should be move(X,0,X).

move([X|_],0,X) will unify X with the single element at the head of the list.