Question

I am new to Prolog and I’m trying to to create function that will simply remove all instances of an element from a list. The following code is what I have so far:

remove([H|T], E, L2) :- (\+ ([H|T] == []) ->
    (H == E
        -> remove(T, E, L2)
        ; append(L2, H, L2), remove(T, E, L2)
    )
    ; append(L2, [])
).

When I run this code on:

remove([1,2,3,4,5], 3, L2).

i get an error:

ERROR: Out of global stack

Could someone point me to why I am getting this problem?

Answer 1

This statement

[H|T] == []

can never be true because an empty list can never be identical to a list that contains at least one element.