(** Compatibility of evaluation functions with the "less defined than" relation. *)

Ltac TrivialExists :=
  match goal with
  | [ |- exists v, Some ?x = Some v /\ _ ] => exists x; split; auto
  | _ => idtac
  end.

Lemma set_optvar_lessdef: forall e1 e2 optid v1 v2, env_lessdef e1 e2 -> Val.lessdef v1 v2 -> env_lessdef (set_optvar optid v1 e1) (set_optvar optid v2 e2).