Prolog separating into two lists issue

Question

I have a prolog assignment.

I need to look at the first item in a list, see if its following items are the same until they are not and separate the lists by the firs

Answer 1

When the first two elements are different you do not need a recursive goal.

grab([], [], []).
grab([A,A|Rest], [A|As], L2):- !, grab([A|Rest], As, L2).
grab([A|Tail], [A], Tail).