proposition: Lemma split_cons : forall x y l r s, (r,s) = split l -> split ((x,y)::l) = (x::r, y::s).
proof: Proof. Proof using. introv H. rewrite split_cons_let. rewrite~ <- H. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)