proposition: Lemma concat_one : forall l, concat (l::nil) = l.
proof: Proof. Proof using. intros. rewrite concat_cons. rewrite concat_nil. rew_list~. Qed.
imports: Coq.Classes.Morphisms TLC(LibTactics LibLogic LibReflect LibOperation LibProd LibOption LibNat LibInt LibWf LibMonoid LibRelation)