sig
type label
type t
val weight : Nonnegative.WEIGHT.label -> Nonnegative.WEIGHT.t
val compare : Nonnegative.WEIGHT.t -> Nonnegative.WEIGHT.t -> int
val add :
Nonnegative.WEIGHT.t -> Nonnegative.WEIGHT.t -> Nonnegative.WEIGHT.t
val zero : Nonnegative.WEIGHT.t
end