proposition: Lemma Forall2_inv_length : forall P r s, Forall2 P r s -> length r = length s.
proof: Proof. Proof using. introv H. induction H; rew_list; math. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)