proposition: Lemma split_length_r : forall l r s, (r,s) = split l -> length s = length l.
proof: Proof. Proof using. introv E. forwards*: split_length E. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)