Module L.
Include Coq.Lists.List.
Definition null {A : Type} (l : list A) : bool :=
match l with
| L.nil => true
| L.cons _ _ => false
end.
#[global] Hint Rewrite null_spec in_map_iff in_app_iff : simplication_hints.
#[global] Hint Rewrite in_remove_iff : simplication_hints.

Lemma rev_inj {A : Type} (xs1 : list A) (xs2 : list A)
(rev_EQ : rev xs1 = rev xs2)
: xs1 = xs2.