Definition IfEq b l1 l2 := L.equal cmp l1 l2 = b.

Lemma equal_cont_IfEq : forall m1 cont e2 l, (forall e, IfEq (cont e) l (flatten_e e)) -> IfEq (equal_cont cmp m1 cont e2) (elements m1 ++ l) (flatten_e e2).