drop
ldrop is like keep, except that it returns the list of values
that do not satisfy the predicate argument.
ldrop(odd, [3, 4, 6, 5, 11, 12, 22, 31])
==> [6, 12, 22]
==> [6, 12, 22]
l is_zero(X)
= X == 0;
drop(is_zero, [4, 6, 2, 0, 1, -5, 0])
==> [4, 6, 2, 1, -5]
drop(is_zero, [4, 6, 2, 0, 1, -5, 0])
==> [4, 6, 2, 1, -5]