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 ('key, 'value, 'identity) t

('key, 'identity) t

'key is the field type

'value is the element type

'identity the identity of the collection

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

The identity needed for making an empty map

val make : id:('k, 'id) id -> ('k, 'v, 'id) t

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

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

isEmpty m checks whether a map m is empty

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

has m k checks whether m has the key k

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

val eqU : ('k, 'v, 'id) t -> ('k, 'v, 'id) t -> ('v -> 'v -> bool) Js.Fn.arity2 -> bool
val eq : ('k, 'v, 'id) t -> ('k, 'v, 'id) t -> ('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.

val findFirstByU : ('k, 'v, 'id) t -> ('k -> 'v -> bool) Js.Fn.arity2 -> ('k * 'v) option
val findFirstBy : ('k, 'v, 'id) t -> ('k -> 'v -> bool) -> ('k * 'v) option

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");;
val forEachU : ('k, 'v, 'id) t -> ('k -> 'v -> unit) Js.Fn.arity2 -> unit
val forEach : ('k, 'v, 'id) t -> ('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"]
val reduceU : ('k, 'v, 'id) t -> 'acc -> ('acc -> 'k -> 'v -> 'acc) Js.Fn.arity3 -> 'acc
val reduce : ('k, 'v, 'id) t -> '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"];;
val everyU : ('k, 'v, 'id) t -> ('k -> 'v -> bool) Js.Fn.arity2 -> bool
val every : ('k, 'v, 'id) t -> ('k -> 'v -> bool) -> bool

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

val someU : ('k, 'v, 'id) t -> ('k -> 'v -> bool) Js.Fn.arity2 -> bool
val some : ('k, 'v, 'id) t -> ('k -> 'v -> bool) -> bool

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

val size : ('k, 'v, 'id) t -> int

size s

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

toArray s

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

In increasing order

See toArray

val fromArray : ('k * 'v) array -> id:('k, 'id) id -> ('k, 'v, 'id) t

fromArray kvs ~id

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

keysToArray s

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

valuesToArray s

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

minKey s

  • returns

    the minimum key, None if not exist

val minKeyUndefined : ('k, _, _) t -> 'k Js.undefined

See minKey

val maxKey : ('k, _, _) t -> 'k option

maxKey s

  • returns

    the maximum key, None if not exist

val maxKeyUndefined : ('k, _, _) t -> 'k Js.undefined

See maxKey

val minimum : ('k, 'v, _) t -> ('k * 'v) option

minimum s

  • returns

    the minimum key value pair, None if not exist

val minUndefined : ('k, 'v, _) t -> ('k * 'v) Js.undefined

See minimum

val maximum : ('k, 'v, _) t -> ('k * 'v) option

maximum s

  • returns

    the maximum key value pair, None if not exist

val maxUndefined : ('k, 'v, _) t -> ('k * 'v) Js.undefined

See maximum

val get : ('k, 'v, 'id) t -> 'k -> 'v option

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;;
val getUndefined : ('k, 'v, 'id) t -> 'k -> 'v Js.undefined

See get

  • returns

    undefined when not found

val getWithDefault : ('k, 'v, 'id) t -> 'k -> 'v -> 'v

getWithDefault s k default

See get

  • returns

    default when k is not found

val getExn : ('k, 'v, 'id) t -> 'k -> 'v

getExn s k

See getExn

raise when k not exist

val remove : ('k, 'v, 'id) t -> 'k -> ('k, 'v, 'id) t

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|];;
val removeMany : ('k, 'v, 'id) t -> 'k array -> ('k, 'v, 'id) t

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

val set : ('k, 'v, 'id) t -> 'k -> 'v -> ('k, 'v, 'id) t

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"];;
val updateU : ('k, 'v, 'id) t -> 'k -> ('v option -> 'v option) Js.Fn.arity1 -> ('k, 'v, 'id) t
val update : ('k, 'v, 'id) t -> 'k -> ('v option -> 'v option) -> ('k, 'v, 'id) t

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.

val mergeMany : ('k, 'v, 'id) t -> ('k * 'v) array -> ('k, 'v, 'id) t

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

val mergeU : ('k, 'v, 'id) t -> ('k, 'v2, 'id) t -> ('k -> 'v option -> 'v2 option -> 'v3 option) Js.Fn.arity3 -> ('k, 'v3, 'id) t
val merge : ('k, 'v, 'id) t -> ('k, 'v2, 'id) t -> ('k -> 'v option -> 'v2 option -> 'v3 option) -> ('k, 'v3, 'id) t

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.

val keepU : ('k, 'v, 'id) t -> ('k -> 'v -> bool) Js.Fn.arity2 -> ('k, 'v, 'id) t
val keep : ('k, 'v, 'id) t -> ('k -> 'v -> bool) -> ('k, 'v, 'id) t

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

val partitionU : ('k, 'v, 'id) t -> ('k -> 'v -> bool) Js.Fn.arity2 -> ('k, 'v, 'id) t * ('k, 'v, 'id) t
val partition : ('k, 'v, 'id) t -> ('k -> 'v -> bool) -> ('k, 'v, 'id) t * ('k, 'v, 'id) t

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.

val split : ('k, 'v, 'id) t -> 'k -> (('k, 'v, 'id) t * ('k, 'v, 'id) t) * 'v option

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.

val mapU : ('k, 'v, 'id) t -> ('v -> 'v2) Js.Fn.arity1 -> ('k, 'v2, 'id) t
val map : ('k, 'v, 'id) t -> ('v -> 'v2) -> ('k, 'v2, 'id) t

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.

val mapWithKeyU : ('k, 'v, 'id) t -> ('k -> 'v -> 'v2) Js.Fn.arity2 -> ('k, 'v2, 'id) t
val mapWithKey : ('k, 'v, 'id) t -> ('k -> 'v -> 'v2) -> ('k, 'v2, 'id) t

mapWithKey m f

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

val getData : ('k, 'v, 'id) t -> ('k, 'v, 'id) Belt_MapDict.t

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

val getId : ('k, 'v, 'id) t -> ('k, 'id) id

getId s0

Advanced usage only

  • returns

    the identity of s0

val packIdData : id:('k, 'id) id -> data:('k, 'v, 'id) Belt_MapDict.t -> ('k, 'v, 'id) t

packIdData ~id ~data

Advanced usage only

  • returns

    the packed collection