#[deprecated(use = snd_list_prod)]
Notation map_snd_list_prod := snd_list_prod (only parsing).
(** Sum of elements of a list of [nat]: [list_sum] *)
Definition list_sum l := fold_right plus 0 l.

Corollary flat_map_constant_length A B c (f: A -> list B) l:
(forall x, In x l -> length (f x) = c) -> length (flat_map f l) = (length l) * c.