(** * Addendum to the standard library of Coq *)
Require Export Omega.
Global Obligation Tactic := idtac.
Notation "[ x ; .. ; y ]" := (cons x .. (cons y nil) .. ).

Lemma map_ext2 : forall {A B} (f g : A -> B) l,
(forall a : A, In a l -> f a = g a) -> map f l = map g l.