proposition: Lemma create_height : forall l x e r, avl l -> avl r -> -(2) <= height l - height r <= 2 -> height (create l x e r) = max (height l) (height r) + 1.
proof: Proof. unfold create; intros; auto. Qed.
imports: FunInd Recdef FMapInterface FMapList ZArith Int FMapAVL Lia