(** The ``is less defined'' relation between values.
    A value is less defined than itself, and [Vundef] is
    less defined than any value. *)

Inductive lessdef: val -> val -> Prop :=
  | lessdef_refl: forall v, lessdef v v
  | lessdef_undef: forall v, lessdef Vundef v.(** The ``is less defined'' relation between values.
    A value is less defined than itself, and [Vundef] is
    less defined than any value. *)

Inductive lessdef: val -> val -> Prop :=
  | lessdef_refl: forall v, lessdef v v
  | lessdef_undef: forall v, lessdef Vundef v.(** The ``is less defined'' relation between values.
    A value is less defined than itself, and [Vundef] is
    less defined than any value. *)

Inductive lessdef: val -> val -> Prop :=
  | lessdef_refl: forall v, lessdef v v
  | lessdef_undef: forall v, lessdef Vundef v.

(* Specifications: *)
Lemma lessdef_same: forall v1 v2, v1 = v2 -> lessdef v1 v2.
Lemma lessdef_trans: forall v1 v2 v3, lessdef v1 v2 -> lessdef v2 v3 -> lessdef v1 v3.