ligo/gitlab-pages/docs/reference/map.md

id	title
map-reference	Map — Hashmaps that it makes sense to iterate over

Defining A Map Type

type move is int * int
type moveset is map(address, move)

type move = int * int
type moveset = (address, move) map

type move = (int, int);
type moveset = map(address, move);

Creating A Map

const moves: moveset = map
    ("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address) -> (1, 2);
    ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address) -> (0, 3);
end

let moves: moveset = Map.literal
  [ (("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address), (1, 2)) ;
    (("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address), (0, 3)) ;
  ]

let moves : moveset =
  Map.literal([
    ("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address, (1, 2)),
    ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address, (0, 3)),
  ]);

Map.find_opt(k: a', m: (a',b') map) : b' option

Retrieve the value associated with a particular key. This version returns an option which can either shift logic in response to a missing value or throw an error.

const my_balance : option(move) = moves[("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address)];

let my_balance : move option = Map.find_opt ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address) moves

let my_balance : option(move) =
  Map.find_opt("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address, moves);

Map.find(k: a', m: (a', b') map) : b'

Forcefully retrieve the value associated with a particular key. If that value doesn't exist, this function throws an error.

const my_balance : move = get_force(("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address), moves);

let my_balance : move = Map.find ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address) moves

let my_balance : move =
  Map.find("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address, moves);

Map.update(k: a', v: b', m: (a', b') map) : (a', b') map

Change the value associated with a particular key, if that value doesn't already exist add it.

The values of a PascaLIGO map can be updated using the ordinary assignment syntax:

function set_ (var m: moveset) : moveset is
  block {
    m[("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address)] := (4,9);
  } with m

We can update a map in CameLIGO using the Map.update built-in:

let updated_map: moveset = Map.update ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address) (Some (4,9)) moves

We can update a map in ReasonLIGO using the Map.update built-in:

let updated_map: moveset = Map.update(("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address), Some((4,9)), moves);

Map.add(k: a', v: b', m: (a', b') map) : (a', b') map

function set_ (var n : int ; var m : map(int, int)) : map(int, int) is block {
  m[23] := n ;
} with m

let add (n,m: int * (int, int) map) : foobar = Map.add 23 n m

let add = (n: int, m: map(int, int)) : foobar => Map.add(23, n, m);

Map.remove(k: a', m: (a', b') map) : (a', b') map

Remove a key and its associated value from the map.

function rm (var m : map(int, int)) : map(int, int) is block {
  remove 42 from map m
} with m

let rm (m: (int, int) map) : (int, int) map = Map.remove 42 m

let rm = (m: map(int, int)): map(int, int) => Map.remove(42, m);

Map.iter(iterator_function: (a', b') -> unit, m: (a', b') map) : unit

Run a function returning unit over the contents of a map's key-value pairs. For example an assertion.

function iter_op (const m : moveset) : unit is
  block {
    function aggregate (const i : address ; const j : move) : unit is block
      { if j.1 > 1 then skip else failwith("fail") } with unit
  } with map_iter(aggregate, m);

let iter_op (m : moveset) : unit =
  let assert_eq = fun (i,j: address * move) -> assert (j.0 > 1)
  in Map.iter assert_eq m

let iter_op = (m: moveset): unit => {
  let assert_eq = ((i,j): (address, move)) => assert (j[0] > 1);
  Map.iter(assert_eq, m);
};

Map.map(mapping_function: (a', b') -> b', m: (a', b') map) : (a', b') map

Update the values associated with every key in the map according to some update rule mapping_function.

function map_op (const m : moveset) : moveset is
  block {
    function increment (const i : address ; const j : move) : move is (j.1, j.2 + 1);
  } with map_map (increment, m);

let map_op (m : moveset) : moveset =
  let increment = fun (i,j: address * move) -> (j.0, j.1 + 1)
  in Map.map increment m

let map_op = (m: moveset): moveset => {
  let increment = ((i,j): (address, move)) => (j[0], j[1] + 1);
  Map.map(increment, m);
};

Map.fold(folding_function: (b', (a', b')) -> b', m: (a', b') map, initial: b') : b'

Combine every value in the map together according to a fold rule folding_function.

function fold_op (const m : moveset) : int is
  block {
    function aggregate (const j : int; const cur : address * (int * int)) : int is j + cur.2.2
  } with map_fold(aggregate, m, 5)

let fold_op (m : moveset) : moveset =
  let aggregate = fun (i,j: int * (address * (int * int))) -> i + j.1.1
  in Map.fold aggregate m 5

let fold_op = (m: moveset): moveset => {
  let aggregate = ((i,j): (int, (address, (int,int)))) => i + j[1][1];
  Map.fold(aggregate, m, 5);
};

Map.mem(k: a', m: (a', b') map) : bool

Test whether a particular key k exists in a given map m.

function mem (const k: int; const m: map(int, int)) : bool is map_mem(k, m)

let mem (k,m: int * (int, int) map) : bool = Map.mem k m

let mem = ((k,m): (int, map(int,int))): bool => Map.mem(k, m);

Map.empty() : (a', b') map

Create an empty map.

const empty_map : map(int, int) = map end

let empty_map : (int, int) map = Map.empty

let empty_map: map(int, int) = Map.empty;

Map.literal(key_value_pair_list: (a', b') list) : (a', b') map

Constructs a map from a list of key-value pair tuples.

const moves: moveset = map
    ("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address) -> (1, 2);
    ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address) -> (0, 3);
end

let moves: moveset = Map.literal
  [ (("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address), (1, 2)) ;
    (("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address), (0, 3)) ;
  ]

let moves : moveset =
  Map.literal([
    ("tz1KqTpEZ7Yob7QbPE4Hy4Wo8fHG8LhKxZSx": address, (1, 2)),
    ("tz1gjaF81ZRRvdzjobyfVNsAeSC6PScjfQwN": address, (0, 3)),
  ]);

Map.size(m: (a', b') map) : nat

Get the size of a given map m.

function size_ (const m : map(int, int)) : nat is
  block {skip} with (size(m))

let size_ (m: (int, int) map) : nat = Map.size m

let size_ = (m: map(int, int)): nat => Map.size(m);