Docs / API / Belt / Map

Map

The top level provides generic immutable map operations.

It also has three specialized inner modules Belt.Map.Int, Belt.Map.String and Belt.Map.Dict.

t

RESCRIPT

type t<'key, 'value, 'identity>

'key is the field type

'value is the element type

'identity the identity of the collection

id

RESCRIPT

type id<'key, 'id> = Belt_Id.comparable<'key, 'id>

The identity needed for making an empty map.

make

RESCRIPT

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

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

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

let m = Belt.Map.make(~id=module(IntCmp))

Belt.Map.set(m, 0, "a")

isEmpty

RESCRIPT

let isEmpty: t<'a, 'b, 'c> => bool

isEmpty(m) checks whether a map m is empty.

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

Belt.Map.isEmpty(Belt.Map.fromArray([(1, "1")], ~id=module(IntCmp))) == false

has

RESCRIPT

let has: (t<'k, 'v, 'id>, 'k) => bool

has(m, k) checks whether m has the key k.

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

Belt.Map.has(Belt.Map.fromArray([(1, "1")], ~id=module(IntCmp)), 1) == true

cmpU

Deprecated

Use cmp instead

RESCRIPT

let cmpU: (t<'k, 'v, 'id>, t<'k, 'v, 'id>, ('v, 'v) => int) => int

cmp

RESCRIPT

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.

eqU

Deprecated

Use eq instead

RESCRIPT

let eqU: (t<'k, 'v, 'id>, t<'k, 'v, 'id>, ('v, 'v) => bool) => bool

eq

RESCRIPT

let eq: (t<'k, 'v, 'id>, t<'k, 'v, 'id>, ('v, 'v) => bool) => bool

eq(m1, m2, veq)tests whether the mapsm1andm2are 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.

findFirstByU

Deprecated

Use findFirstBy instead

RESCRIPT

let findFirstByU: (t<'k, 'v, 'id>, ('k, 'v) => bool) => option<('k, 'v)>

findFirstBy

RESCRIPT

let findFirstBy: (t<'k, 'v, 'id>, ('k, 'v) => bool) => option<('k, 'v)>

findFirstBy(m, p) uses function f to find the first key value pair to match predicate p.

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

let s0 = Belt.Map.fromArray(~id=module(IntCmp), [(4, "4"), (1, "1"), (2, "2"), (3, "")])

s0->Belt.Map.findFirstBy((k, _) => k == 4) == Some(4, "4")

forEachU

Deprecated

Use forEach instead

RESCRIPT

let forEachU: (t<'k, 'v, 'id>, ('k, 'v) => unit) => unit

forEach

RESCRIPT

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.

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

let s0 = Belt.Map.fromArray(~id=module(IntCmp), [(4, "4"), (1, "1"), (2, "2"), (3, "3")])

let acc = ref(list{})

Belt.Map.forEach(s0, (k, v) => acc := list{(k, v), ...acc.contents})

acc.contents == list{(4, "4"), (3, "3"), (2, "2"), (1, "1")}

reduceU

Deprecated

Use reduce instead

RESCRIPT

let reduceU: (t<'k, 'v, 'id>, 'acc, ('acc, 'k, 'v) => 'acc) => 'acc

reduce

RESCRIPT

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.

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

let s0 = Belt.Map.fromArray(~id=module(IntCmp), [(4, "4"), (1, "1"), (2, "2"), (3, "3")])

Belt.Map.reduce(s0, list{}, (acc, k, v) => list{(k, v), ...acc}) ==
  list{(4, "4"), (3, "3"), (2, "2"), (1, "1")}

everyU

Deprecated

Use every instead

RESCRIPT

let everyU: (t<'k, 'v, 'id>, ('k, 'v) => bool) => bool

every

RESCRIPT

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

someU

Deprecated

Use some instead

RESCRIPT

let someU: (t<'k, 'v, 'id>, ('k, 'v) => bool) => bool

some

RESCRIPT

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

size

RESCRIPT

let size: t<'k, 'v, 'id> => int

size(s)

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

Belt.Map.size(Belt.Map.fromArray([(2, "2"), (2, "1"), (3, "3")], ~id=module(IntCmp))) == 2

toArray

RESCRIPT

let toArray: t<'k, 'v, 'id> => array<('k, 'v)>

toArray(s)

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

Belt.Map.toArray(Belt.Map.fromArray([(2, "2"), (1, "1"), (3, "3")], ~id=module(IntCmp))) == [
    (1, "1"),
    (2, "2"),
    (3, "3"),
  ]

toList

RESCRIPT

let toList: t<'k, 'v, 'id> => list<('k, 'v)>

In increasing order. See Belt.Map.toArray

fromArray

RESCRIPT

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

fromArray(kvs, ~id);

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

Belt.Map.toArray(Belt.Map.fromArray([(2, "2"), (1, "1"), (3, "3")], ~id=module(IntCmp))) == [
    (1, "1"),
    (2, "2"),
    (3, "3"),
  ]

keysToArray

RESCRIPT

let keysToArray: t<'k, 'v, 'id> => array<'k>

keysToArray(s);

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

Belt.Map.keysToArray(Belt.Map.fromArray([(2, "2"), (1, "1"), (3, "3")], ~id=module(IntCmp))) == [
    1,
    2,
    3,
  ]

valuesToArray

RESCRIPT

let valuesToArray: t<'k, 'v, 'id> => array<'v>

valuesToArray(s);

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

Belt.Map.valuesToArray(Belt.Map.fromArray([(2, "2"), (1, "1"), (3, "3")], ~id=module(IntCmp))) == [
    "1",
    "2",
    "3",
  ]

minKey

RESCRIPT

let minKey: t<'k, 'a, 'b> => option<'k>

minKey(s) returns the minimum key, None if not exist.

minKeyUndefined

RESCRIPT

let minKeyUndefined: t<'k, 'a, 'b> => Js.undefined<'k>

See Belt.Map.minKey

maxKey

RESCRIPT

let maxKey: t<'k, 'a, 'b> => option<'k>

maxKey(s) returns the maximum key, None if not exist.

maxKeyUndefined

RESCRIPT

let maxKeyUndefined: t<'k, 'a, 'b> => Js.undefined<'k>

See Belt.Map.maxKey

minimum

RESCRIPT

let minimum: t<'k, 'v, 'a> => option<('k, 'v)>

minimum(s) returns the minimum key value pair, None if not exist.

minUndefined

RESCRIPT

let minUndefined: t<'k, 'v, 'a> => Js.undefined<('k, 'v)>

See Belt.Map.minimum

maximum

RESCRIPT

let maximum: t<'k, 'v, 'a> => option<('k, 'v)>

maximum(s) returns the maximum key value pair, None if not exist.

maxUndefined

RESCRIPT

let maxUndefined: t<'k, 'v, 'a> => Js.undefined<('k, 'v)>

See Belt.Map.maximum

get

RESCRIPT

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

get(s, k)

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

Belt.Map.get(Belt.Map.fromArray([(2, "2"), (1, "1"), (3, "3")], ~id=module(IntCmp)), 2) == Some("2")

Belt.Map.get(Belt.Map.fromArray([(2, "2"), (1, "1"), (3, "3")], ~id=module(IntCmp)), 4) == None

getUndefined

RESCRIPT

let getUndefined: (t<'k, 'v, 'id>, 'k) => Js.undefined<'v>

See Belt.Map.get. Returns undefined when not found

getWithDefault

RESCRIPT

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

getWithDefault(s, k, default)

See Belt.Map.get

Returns default when k is not found.

getExn

RESCRIPT

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

getExn(s, k)

See Belt.Map.get

throw when k not exist

getOrThrow

RESCRIPT

let getOrThrow: (t<'k, 'v, 'id>, 'k) => 'v

getOrThrow(s, k)

See Belt.Map.get

throw when k not exist

remove

RESCRIPT

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.

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

let s0 = Belt.Map.fromArray([(2, "2"), (1, "1"), (3, "3")], ~id=module(IntCmp))

let s1 = Belt.Map.remove(s0, 1)

let s2 = Belt.Map.remove(s1, 1)

s1 == s2

Belt.Map.keysToArray(s1) == [2, 3]

removeMany

RESCRIPT

let removeMany: (t<'k, 'v, 'id>, array<'k>) => t<'k, 'v, 'id>

removeMany(s, xs)

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

set

RESCRIPT

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.

Examples

RESCRIPT
module IntCmp = Belt.Id.MakeComparable({
  type t = int
  let cmp = (a, b) => Pervasives.compare(a, b)
})

let s0 = Belt.Map.fromArray([(2, "2"), (1, "1"), (3, "3")], ~id=module(IntCmp))

let s1 = Belt.Map.set(s0, 2, "3")

Belt.Map.valuesToArray(s1) == ["1", "3", "3"]

updateU

Deprecated

Use update instead

RESCRIPT

let updateU: (
  t<'k, 'v, 'id>,
  'k,
  option<'v> => option<'v>,
) => t<'k, 'v, 'id>

update

RESCRIPT

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(m, x)), 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.

mergeMany

RESCRIPT

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.

mergeU

Deprecated

Use merge instead

RESCRIPT

let mergeU: (
  t<'k, 'v, 'id>,
  t<'k, 'v2, 'id>,
  ('k, option<'v>, option<'v2>) => option<'v3>,
) => t<'k, 'v3, 'id>

merge

RESCRIPT

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.

keepU

Deprecated

Use keep instead

RESCRIPT

let keepU: (t<'k, 'v, 'id>, ('k, 'v) => bool) => t<'k, 'v, 'id>

keep

RESCRIPT

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.

partitionU

Deprecated

Use partition instead

RESCRIPT

let partitionU: (
  t<'k, 'v, 'id>,
  ('k, 'v) => bool,
) => (t<'k, 'v, 'id>, t<'k, 'v, 'id>)

partition

RESCRIPT

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.

split

RESCRIPT

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.

mapU

Deprecated

Use map instead

RESCRIPT

let mapU: (t<'k, 'v, 'id>, 'v => 'v2) => t<'k, 'v2, 'id>

map

RESCRIPT

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.

mapWithKeyU

Deprecated

Use mapWithKey instead

RESCRIPT

let mapWithKeyU: (t<'k, 'v, 'id>, ('k, 'v) => 'v2) => t<'k, 'v2, 'id>

mapWithKey

RESCRIPT

let mapWithKey: (t<'k, 'v, 'id>, ('k, 'v) => 'v2) => t<'k, 'v2, 'id>

mapWithKey(m, f)

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

getData

RESCRIPT

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.

getId

RESCRIPT

let getId: t<'k, 'v, 'id> => id<'k, 'id>

Advanced usage only. Returns the identity of s0.

packIdData

RESCRIPT

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.

checkInvariantInternal

RESCRIPT

let checkInvariantInternal: t<'a, 'b, 'c> => unit

throw when invariant is not held