Section ordre.
Variable A : Set.
Variable f g : A -> nat.
Definition e_lexfg (a b : A) := f a > f b \/ f a = f b /\ g a > g b.
End ordre.
Notation lexfg := (e_lexfg _) (only parsing).
(* <Warning> : Syntax is discontinued *)
Hint Resolve lexfg_systemSL.

Theorem lexfg_app_l :
forall a a' b : terms,
e_lexfg _ (e_P1 wt) (e_P2 wt) a a' ->
e_lexfg _ (e_P1 wt) (e_P2 wt) (app a b) (app a' b).