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
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.
('a, 'id) hash
Its runtime represenation is a hash
function, but signed with a type parameter, so that different hash functions type mismatch
('a, 'id) eq
Its runtime represenation is an eq
function, but signed with a type parameter, so that different hash functions type mismatch
('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 = { ... };
type comparable('key, 'id) =
(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
orcomparable
.
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: { ... }) => Comparable with type t = M.t;
module MakeComparable: (M: { ... }) => Comparable with type t = M.t;
let comparableU:
cmp:Js.Fn.arity2(('a => 'a => int)) =>
(module Comparable
with type t = 'a);
let 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 = { ... };
('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: { ... }) => Hashable with type t = M.t;
module MakeHashable: (M: { ... }) => Hashable with type t = M.t;
let hashableU:
hash:Js.Fn.arity1(('a => int)) =>
eq:Js.Fn.arity2(('a => 'a => bool)) =>
(module Hashable
with type t = 'a);