Inductive list_order {A : Type} (R : A -> A -> Prop) : list A -> list A -> Prop :=
| lo_cons:  forall l1 l2 h, Forall (fun x => R x h) l1 -> list_order R (l1 ++ l2) (h :: l2).
Definition W {A : Type} (R : A -> A -> Prop) (l : list A) : Prop :=
Acc (list_order R) l.
(*  forall l', list_order R l' l -> Acc (list_order R) l'. *)

Lemma deuxpointun (A : Type) (R : A -> A -> Prop) (l : list A) (a : A) :
(forall b, R b a -> forall l', W R l' -> W R (b :: l')) ->
W R l (* /\
(forall l', list_order R l' l -> W R (a :: l')) *) ->
W R (a :: l).