?- append(cons(1, cons(2, nil)), cons(3, nil), L).
L = cons(1, cons(2, cons(3, nil)))
?- append(X, Y, cons(a, cons(b, nil))).
X = nil, Y = cons(a, cons(b, nil))
X = cons(a, nil), Y = cons(b, nil)
X = cons(a, cons(b, nil)), Y = nil
?- member(X, cons(a, cons(b, cons(c, nil)))).
X = a
X = b
X = c
?- member(b, cons(a, cons(b, cons(c, nil)))).
true
?- reverse(cons(1, cons(2, cons(3, nil))), R).
R = cons(3, cons(2, cons(1, nil)))
?- length(cons(a, cons(b, nil)), N).
N = s(s(zero))
?- length(L, s(s(zero))).
L = cons(_1, cons(_2, nil))