Module Base.Comparator

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 ‑> Sexp.t;

}

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

module type S : sig ... end

module type S1 : sig ... end

module type S_fc : sig ... end

val make : compare:('a ‑> 'a ‑> int) ‑> sexp_of_t:('a ‑> Sexp.t) ‑> (module S_fc with type comparable_t = 'a)

make creates a comparator witness for the given comparison. It is intended as a lightweight alternative to the functors below, to be used like so: include (val Comparator.make ~compare ~sexp_of_t)

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

module Make : functor (M : sig ... end) -> S with type t := M.t

Make creates a comparator value and its phantom comparator_witness type for a nullary type.

module Make1 : functor (M : sig ... end) -> S1 with type a t := a M.t

Make1 creates a comparator value and its phantom comparator_witness type for a unary type. It takes a compare and sexp_of_t that have non-standard types because the Comparator.t type doesn't allow passing in additional values for the type argument.