proposition: Theorem list_cons_iso : forall a, one + (a * list a) ≅ list a.
proof: Proof. intros. exists (fun p => match p with | inl _ => nil | inr (x, xs) => cons x xs end). exists (fun p => match p with | nil => inl tt | cons x xs => inr (x, xs) end). extensionalize. Qed.
imports: Hask.Ltac Hask.Prelude Hask.Control.Applicative Hask.Control.Monad Hask.Control.Monad.Cont Hask.Control.Monad.State Hask.Data.Functor.Contravariant Hask.Data.Functor.Identity Hask.Data.Functor.Kan Hask.Data.Functor.Yoneda Hask.Control.Lens Coq.Classes.Morphisms Coq.Setoids.Setoid Coq.Init.Datatypes Coq.Relations.Relation_Definitions FunctionalExtensionality