Module Comparator

module Comparator: sig .. end

A type-indexed value that allows one to compare (and for generating error messages, serialize) values of the type in question.

One of the type parameters is a phantom parameter used to distinguish comparators potentially built on different comparison functions. In particular, we want to distinguish those using polymorphic compare and those using a monomorphic compare.

type ('a, 'witness) t = private {

	`compare :'a -> 'a -> int;`
	`sexp_of_t :'a -> Sexplib.Sexp.t;`

}

type ('a, 'b) comparator = ('a, 'b) t

module type S = sig .. end

module type S1 = sig .. end

module Poly: S1  with type 'a t = 'a

module S_to_S1: functor (S : S) -> S1 
  with type 'a t = S.t 
  with type comparator_witness = S.comparator_witness

The Make functors mint fresh types that are used as the phantom comparator_witnesses.

module Make: functor (M : sigtype t 

val sexp_of_t : t -> Sexplib.Sexp.t
val compare : t -> t -> int
end) -> S  with type t := M.t

module Make1: functor (M : sigtype 'a t 

val compare : 'a t -> 'a t -> int
val sexp_of_t : 'a t -> Sexplib.Sexp.t
end) -> S1  with type 'a t := 'a M.t