proposition: Lemma alt_endo_nothing {c} (m n : Maybe c) : m <|> n = Nothing <-> m = Nothing /\ n = Nothing.
proof: Proof. induction m, n; simpl; intuition auto; discriminate. Qed.
imports: Category.Lib Category.Theory.Functor Category.Theory.Coq.Functor.Proofs Category.Theory.Coq.Applicative.Proofs Category.Theory.Coq.Monad.Proofs Category.Theory.Coq.Maybe