Module Belt.Id

Belt.Id

Provide utilities to create identified comparators or hashes for data structures used below.

It create a unique identifier per module of functions so that different data structures with slightly different comparison functions won't mix

Belt.Id

Provide utiliites to create identified comparators or hashes for data structures used below.

It create a unique identifer per module of functions so that different data structures with slightly different comparison functions won't mix.

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)