Id (melange.Belt.Id)

type ('a, 'id) hash

('a, 'id) hash

Its runtime represenation is a hash function, but signed with a type parameter, so that different hash functions type mismatch

type ('a, 'id) eq

('a, 'id) eq

Its runtime represenation is an eq function, but signed with a type parameter, so that different hash functions type mismatch

type ('a, 'id) cmp

('a,'id) cmp

Its runtime representation is a cmp function, but signed with a type parameter, so that different hash functions type mismatch

module type Comparable = sig ... end

type ('key, 'id) comparable =
  (module Comparable
  with type identity = 'id
   and type t = 'key)

('key, 'id) cmparable is a module of functions, here it only includes cmp.

Unlike normal functions, when created, it comes with a unique identity (guaranteed by the type system).

It can be created using function comparableU or comparable.

The idea of a unique identity when created is that it makes sure two sets would type mismatch if they use different comparison function

module MakeComparableU (M : sig ... end) : Comparable with type t = M.t

module MakeComparable (M : sig ... end) : Comparable with type t = M.t

val comparableU : 
  cmp:('a -> 'a -> int) Js.Fn.arity2 ->
  (module Comparable
  with type t = 'a)

val comparable : cmp:('a -> 'a -> int) -> (module Comparable with type t = 'a)

module C = (
  val Belt.Id.comparable ~cmp:(compare : int -> int -> int)
)
let m = Belt.Set.make(module C)

Note that the name of C can not be ignored

module type Hashable = sig ... end

type ('key, 'id) hashable =
  (module Hashable
  with type identity = 'id
   and type t = 'key)

('key, 'id) hashable is a module of functions, here it only includes hash, eq.

Unlike normal functions, when created, it comes with a unique identity (guaranteed by the type system).

It can be created using function hashableU or hashable.

The idea of a unique identity when created is that it makes sure two hash sets would type mismatch if they use different comparison function

module MakeHashableU (M : sig ... end) : Hashable with type t = M.t

module MakeHashable (M : sig ... end) : Hashable with type t = M.t

val hashableU : 
  hash:('a -> int) Js.Fn.arity1 ->
  eq:('a -> 'a -> bool) Js.Fn.arity2 ->
  (module Hashable
  with type t = 'a)

val hashable : 
  hash:('a -> int) ->
  eq:('a -> 'a -> bool) ->
  (module Hashable
  with type t = 'a)