int_mul@{} (x y : Int) : Int. Proof. induction x as [|x IHx|x IHx] in y |- *. - exact 0. - exact (y + IHx y). - exact (-y + IHx y). Defined.
Require Import Basics.Overture Basics.Nat Basics.Tactics Basics.Decidable Basics.Equivalences Basics.PathGroupoids Types.Paths Types.Universe. Require Import Spaces.Nat.Core.