Module Belt_Map

A immutable sorted map module which allows customize compare behavior.

The implementation uses balanced binary trees, and therefore searching and insertion take time logarithmic in the size of the map.

For more info on this module's usage of identity, `make` and others, please see the top level documentation of Belt, A special encoding for collection safety.

Example usage:

module PairComparator = Belt.Id.MakeComparable(struct
  type t = int * int
  let cmp (a0, a1) (b0, b1) =
    match Pervasives.compare a0 b0 with
    | 0 -> Pervasives.compare a1 b1
    | c -> c
end)

let myMap = Belt.Map.make ~id:(module PairComparator)
let myMap2 = Belt.Map.set myMap (1, 2) "myValue"

The API documentation below will assume a predeclared comparator module for integers, IntCmp

module Int = Belt_MapInt;

Specalized when key type is int, more efficient than the generic type, its compare behavior is fixed using the built-in comparison

module String = Belt_MapString;

specalized when key type is string, more efficient than the generic type, its compare behavior is fixed using the built-in comparison

module Dict = Belt_MapDict;

This module seprate identity from data, it is a bit more verboe but slightly more efficient due to the fact that there is no need to pack identity and data back after each operation

type t('key, 'value, 'identity);

('key, 'identity) t

'key is the field type

'value is the element type

'identity the identity of the collection

type id('key, 'id) = Belt_Id.comparable('key, 'id);

The identity needed for making an empty map

let make: id:id('k, 'id) => t('k, 'v, 'id);

make ~id creates a new map by taking in the comparator

let m = Belt.Map.make ~id:(module IntCmp)
let isEmpty: t(_, _, _) => bool;

isEmpty m checks whether a map m is empty

isEmpty (fromArray [|1,"1"|] ~id:(module IntCmp)) = false
let has: t('k, 'v, 'id) => 'k => bool;

has m k checks whether m has the key k

has (fromArray [|1,"1"|] ~id:(module IntCmp)) 1 = true
let cmpU: t('k, 'v, 'id) => t('k, 'v, 'id) => Js.Fn.arity2(('v => 'v => int)) => int;
let cmp: t('k, 'v, 'id) => t('k, 'v, 'id) => ('v => 'v => int) => int;

cmp m0 m1 vcmp

Total ordering of map given total ordering of value function.

It will compare size first and each element following the order one by one.

let eqU: t('k, 'v, 'id) => t('k, 'v, 'id) => Js.Fn.arity2(('v => 'v => bool)) => bool;
let eq: t('k, 'v, 'id) => t('k, 'v, 'id) => ('v => 'v => bool) => bool;

eq m1 m2 veq tests whether the maps m1 and m2 are equal, that is, contain equal keys and associate them with equal data. veq is the equality predicate used to compare the data associated with the keys.

let findFirstByU: t('k, 'v, 'id) => Js.Fn.arity2(('k => 'v => bool)) => option(('k, 'v));
let findFirstBy: t('k, 'v, 'id) => ('k => 'v => bool) => option(('k, 'v));

findFirstBy m p uses funcion f to find the first key value pair to match predicate p.

let s0 = fromArray ~id:(module IntCmp) [|4,"4";1,"1";2,"2,"3""|];;
findFirstBy s0 (fun k v -> k = 4 ) = option (4, "4");;
let forEachU: t('k, 'v, 'id) => Js.Fn.arity2(('k => 'v => unit)) => unit;
let forEach: t('k, 'v, 'id) => ('k => 'v => unit) => unit;

forEach m f applies f to all bindings in map m. f receives the 'k as first argument, and the associated value as second argument. The bindings are passed to f in increasing order with respect to the ordering over the type of the keys.

let s0 = fromArray ~id:(module IntCmp) [|4,"4";1,"1";2,"2,"3""|];;
let acc = ref [] ;;
forEach s0 (fun k v -> acc := (k,v) :: !acc);;

!acc = [4,"4"; 3,"3"; 2,"2"; 1,"1"]
let reduceU: t('k, 'v, 'id) => 'acc => Js.Fn.arity3(('acc => 'k => 'v => 'acc)) => 'acc;
let reduce: t('k, 'v, 'id) => 'acc => ('acc => 'k => 'v => 'acc) => 'acc;

reduce m a f computes (f kN dN ... (f k1 d1 a)...), where k1 ... kN are the keys of all bindings in m (in increasing order), and d1 ... dN are the associated data.

let s0 = fromArray ~id:(module IntCmp) [|4,"4";1,"1";2,"2,"3""|];;
reduce s0 [] (fun acc k v -> (k,v) acc ) = [4,"4";3,"3";2,"2";1,"1"];;
let everyU: t('k, 'v, 'id) => Js.Fn.arity2(('k => 'v => bool)) => bool;
let every: t('k, 'v, 'id) => ('k => 'v => bool) => bool;

every m p checks if all the bindings of the map satisfy the predicate p. Order unspecified

let someU: t('k, 'v, 'id) => Js.Fn.arity2(('k => 'v => bool)) => bool;
let some: t('k, 'v, 'id) => ('k => 'v => bool) => bool;

some m p checks if at least one binding of the map satisfy the predicate p. Order unspecified

let size: t('k, 'v, 'id) => int;

size s

size (fromArray [2,"2"; 2,"1"; 3,"3"] ~id:(module IntCmp)) = 2 ;;
let toArray: t('k, 'v, 'id) => array(('k, 'v));

toArray s

toArray (fromArray [2,"2"; 1,"1"; 3,"3"] ~id:(module IntCmp)) = [1,"1";2,"2";3,"3"]
let toList: t('k, 'v, 'id) => list(('k, 'v));

In increasing order

See toArray

let fromArray: array(('k, 'v)) => id:id('k, 'id) => t('k, 'v, 'id);

fromArray kvs ~id

toArray (fromArray [2,"2"; 1,"1"; 3,"3"] ~id:(module IntCmp)) = [1,"1";2,"2";3,"3"]
let keysToArray: t('k, 'v, 'id) => array('k);

keysToArray s

keysToArray (fromArray [2,"2"; 1,"1"; 3,"3"] ~id:(module IntCmp)) =
[|1;2;3|];;
let valuesToArray: t('k, 'v, 'id) => array('v);

valuesToArray s

valuesToArray (fromArray [2,"2"; 1,"1"; 3,"3"] ~id:(module IntCmp)) =
[|"1";"2";"3"|];;
let minKey: t('k, _, _) => option('k);

minKey s

  • returns

    the minimum key, None if not exist

let minKeyUndefined: t('k, _, _) => Js.undefined('k);

See minKey

let maxKey: t('k, _, _) => option('k);

maxKey s

  • returns

    the maximum key, None if not exist

let maxKeyUndefined: t('k, _, _) => Js.undefined('k);

See maxKey

let minimum: t('k, 'v, _) => option(('k, 'v));

minimum s

  • returns

    the minimum key value pair, None if not exist

let minUndefined: t('k, 'v, _) => Js.undefined(('k, 'v));

See minimum

let maximum: t('k, 'v, _) => option(('k, 'v));

maximum s

  • returns

    the maximum key value pair, None if not exist

let maxUndefined: t('k, 'v, _) => Js.undefined(('k, 'v));

See maximum

let get: t('k, 'v, 'id) => 'k => option('v);

get s k

get (fromArray [2,"2"; 1,"1"; 3,"3"] ~id:(module IntCmp)) 2 =
Some "2";;
get (fromArray [2,"2"; 1,"1"; 3,"3"] ~id:(module IntCmp)) 2 =
None;;
let getUndefined: t('k, 'v, 'id) => 'k => Js.undefined('v);

See get

  • returns

    undefined when not found

let getWithDefault: t('k, 'v, 'id) => 'k => 'v => 'v;

getWithDefault s k default

See get

  • returns

    default when k is not found

let getExn: t('k, 'v, 'id) => 'k => 'v;

getExn s k

See getExn

raise when k not exist

let remove: t('k, 'v, 'id) => 'k => t('k, 'v, 'id);

remove m x when x is not in m, m is returned reference unchanged.

let s0 =  (fromArray [2,"2"; 1,"1"; 3,"3"] ~id:(module IntCmp));;

let s1 = remove s0 1;;
let s2 = remove s1 1;;
s1 == s2 ;;
keysToArray s1 = [|2;3|];;
let removeMany: t('k, 'v, 'id) => array('k) => t('k, 'v, 'id);

removeMany s xs

Removing each of xs to s, note unlike remove, the reference of return value might be changed even if none in xs exists s

let set: t('k, 'v, 'id) => 'k => 'v => t('k, 'v, 'id);

set m x y returns a map containing the same bindings as m, with a new binding of x to y. If x was already bound in m, its previous binding disappears.

let s0 =  (fromArray [2,"2"; 1,"1"; 3,"3"] ~id:(module IntCmp));;

let s1 = set s0 2 "3";;

valuesToArray s1 =  ["1";"3";"3"];;
let updateU: t('k, 'v, 'id) => 'k => Js.Fn.arity1((option('v) => option('v))) => t('k, 'v, 'id);
let update: t('k, 'v, 'id) => 'k => (option('v) => option('v)) => t('k, 'v, 'id);

update m x f returns a map containing the same bindings as m, except for the binding of x. Depending on the value of y where y is f (get x m), the binding of x is added, removed or updated. If y is None, the binding is removed if it exists; otherwise, if y is Some z then x is associated to z in the resulting map.

let mergeMany: t('k, 'v, 'id) => array(('k, 'v)) => t('k, 'v, 'id);

mergeMany s xs

Adding each of xs to s, note unlike add, the reference of return value might be changed even if all values in xs exist s

let mergeU: t('k, 'v, 'id) => t('k, 'v2, 'id) => Js.Fn.arity3(('k => option('v) => option('v2) => option('v3))) => t('k, 'v3, 'id);
let merge: t('k, 'v, 'id) => t('k, 'v2, 'id) => ('k => option('v) => option('v2) => option('v3)) => t('k, 'v3, 'id);

merge m1 m2 f computes a map whose keys is a subset of keys of m1 and of m2. The presence of each such binding, and the corresponding value, is determined with the function f.

let keepU: t('k, 'v, 'id) => Js.Fn.arity2(('k => 'v => bool)) => t('k, 'v, 'id);
let keep: t('k, 'v, 'id) => ('k => 'v => bool) => t('k, 'v, 'id);

keep m p returns the map with all the bindings in m that satisfy predicate p.

let partitionU: t('k, 'v, 'id) => Js.Fn.arity2(('k => 'v => bool)) => (t('k, 'v, 'id), t('k, 'v, 'id));
let partition: t('k, 'v, 'id) => ('k => 'v => bool) => (t('k, 'v, 'id), t('k, 'v, 'id));

partition m p returns a pair of maps (m1, m2), where m1 contains all the bindings of s that satisfy the predicate p, and m2 is the map with all the bindings of s that do not satisfy p.

let split: t('k, 'v, 'id) => 'k => ((t('k, 'v, 'id), t('k, 'v, 'id)), option('v));

split x m returns a tuple (l r), data, where l is the map with all the bindings of m whose 'k is strictly less than x; r is the map with all the bindings of m whose 'k is strictly greater than x; data is None if m contains no binding for x, or Some v if m binds v to x.

let mapU: t('k, 'v, 'id) => Js.Fn.arity1(('v => 'v2)) => t('k, 'v2, 'id);
let map: t('k, 'v, 'id) => ('v => 'v2) => t('k, 'v2, 'id);

map m f returns a map with same domain as m, where the associated value a of all bindings of m has been replaced by the result of the application of f to a. The bindings are passed to f in increasing order with respect to the ordering over the type of the keys.

let mapWithKeyU: t('k, 'v, 'id) => Js.Fn.arity2(('k => 'v => 'v2)) => t('k, 'v2, 'id);
let mapWithKey: t('k, 'v, 'id) => ('k => 'v => 'v2) => t('k, 'v2, 'id);

mapWithKey m f

The same as map except that f is supplied with one more argument: the key

let getData: t('k, 'v, 'id) => Belt_MapDict.t('k, 'v, 'id);

getData s0

Advanced usage only

  • returns

    the raw data (detached from comparator), but its type is still manifested, so that user can pass identity directly without boxing

let getId: t('k, 'v, 'id) => id('k, 'id);

getId s0

Advanced usage only

  • returns

    the identity of s0

let packIdData: id:id('k, 'id) => data:Belt_MapDict.t('k, 'v, 'id) => t('k, 'v, 'id);

packIdData ~id ~data

Advanced usage only

  • returns

    the packed collection