(* Lemmas about ident lists *)

Fixpoint id_in_list (id: ident) (ids: list ident) : bool :=
 match ids with i::ids' => orb (Pos.eqb id i) (id_in_list id ids') | _ => false end.Fixpoint compute_list_norepet (ids: list ident) : bool :=
 match ids with
 | id :: ids' => if id_in_list id ids' then false else compute_list_norepet ids'
 | nil => true
 end.

Lemma id_in_list_false: forall i ids, id_in_list i ids = false -> ~In i ids.