Arguments set {A} {dom} x v m _.

Corollary constant_OK : forall A dom v, OK dom (Dom.fold (fun x m => S.add x v m) dom (S.empty A)).
Definition constant (A : Type) dom (v : A) : t A dom :=
exist (OK dom) (Dom.fold (fun x m => S.add x v m) dom (@S.empty A)) (constant_OK dom v).