Prolog append with cut operator

Question

What problem can occur when we use append with cut operator?

   append2([],L,L):-!.
   append2([H|T],L,[H|TL]):-append2(T,L,TL).

I have tri

Answer 1

It won't work when the first two arguments are variable:

?- append(X, Y, [1, 2, 3]).
X = [],
Y = [1, 2, 3] ;
X = [1],
Y = [2, 3] ;
X = [1, 2],
Y = [3] ;
X = [1, 2, 3],
Y = [] ;
false.

?- append2(X, Y, [1, 2, 3]).
X = [],
Y = [1, 2, 3].