(** Nullity Test *)

Definition if_zero (A : Type) (a b : A) (n : N.t) : A :=
  recursion a (fun _ _ => b) n.#[global]
Instance if_zero_wd (A : Type) :
 Proper (Logic.eq ==> Logic.eq ==> N.eq ==> Logic.eq) (@if_zero A).

Theorem if_zero_0 : forall (A : Type) (a b : A), if_zero a b 0 = a.