take: New function

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
drop: New function

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
zero?: New function

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>
empty?: New function

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>