(** Measure over types *)
Parameter max_weight: nat.

(* Specifications: *)
Axiom weight_range: forall t, weight t <= max_weight.
Axiom weight_sub: forall x y, sub x y -> weight x <= weight y.
Axiom weight_sub_strict: forall x y, sub x y -> x <> y -> weight x < weight y.
End TYPE_ALGEBRA.