/
map.gleam
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map.gleam
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import gleam/result
import gleam/option.{Option}
import gleam/list
import gleam/pair
/// A dictionary of keys and values.
///
/// Any type can be used for the keys and values of a map, but all the keys
/// must be of the same type and all the values must be of the same type.
///
/// Each key can only be present in a map once.
///
/// Maps are not ordered in any way, and any unintentional ordering is not to
/// be relied upon in your code as it may change in future versions of Erlang
/// or Gleam.
///
/// See [the Erlang map module](https://erlang.org/doc/man/maps.html) for more
/// information.
///
pub external type Map(key, value)
/// Determines the number of key-value pairs in the map.
/// This function runs in constant time and does not need to iterate the map.
///
/// ## Examples
///
/// > new() |> size()
/// 0
///
/// > new() |> insert("key", "value") |> size()
/// 1
///
///
pub fn size(map: Map(k, v)) -> Int {
do_size(map)
}
if erlang {
external fn do_size(Map(k, v)) -> Int =
"maps" "size"
}
if javascript {
external fn do_size(Map(k, v)) -> Int =
"../gleam_stdlib.js" "map_size"
}
/// Converts the map to a list of 2-element tuples `#(key, value)`, one for
/// each key-value pair in the map.
///
/// The tuples in the list have no specific order.
///
/// ## Examples
///
/// > new() |> to_list()
/// []
///
/// > new() |> insert("key", 0) |> to_list()
/// [#("key", 0)]
///
pub fn to_list(map: Map(key, value)) -> List(#(key, value)) {
do_to_list(map)
}
if erlang {
external fn do_to_list(Map(key, value)) -> List(#(key, value)) =
"maps" "to_list"
}
if javascript {
external fn do_to_list(Map(key, value)) -> List(#(key, value)) =
"../gleam_stdlib.js" "map_to_list"
}
/// Converts a list of 2-element tuples `#(key, value)` to a map.
///
/// If two tuples have the same key the last one in the list will be the one
/// that is present in the map.
///
pub fn from_list(list: List(#(k, v))) -> Map(k, v) {
do_from_list(list)
}
if erlang {
external fn do_from_list(List(#(key, value))) -> Map(key, value) =
"maps" "from_list"
}
if javascript {
fn do_from_list(list: List(#(k, v))) -> Map(k, v) {
list.fold(list, new(), insert_pair)
}
}
/// Determines whether or not a value present in the map for a given key.
///
/// ## Examples
///
/// > new() |> insert("a", 0) |> has_key("a")
/// True
///
/// > new() |> insert("a", 0) |> has_key("b")
/// False
///
pub fn has_key(map: Map(k, v), key: k) -> Bool {
do_has_key(key, map)
}
if erlang {
external fn do_has_key(key, Map(key, v)) -> Bool =
"maps" "is_key"
}
if javascript {
fn do_has_key(key: k, map: Map(k, v)) -> Bool {
get(map, key) != Error(Nil)
}
}
/// Creates a fresh map that contains no values.
///
pub fn new() -> Map(key, value) {
do_new()
}
if erlang {
external fn do_new() -> Map(key, value) =
"maps" "new"
}
if javascript {
external fn do_new() -> Map(key, value) =
"../gleam_stdlib.js" "new_map"
}
/// Fetches a value from a map for a given key.
///
/// The map may not have a value for the key, so the value is wrapped in a
/// Result.
///
/// ## Examples
///
/// > new() |> insert("a", 0) |> get("a")
/// Ok(0)
///
/// > new() |> insert("a", 0) |> get("b")
/// Error(Nil)
///
pub fn get(from: Map(key, value), get: key) -> Result(value, Nil) {
do_get(from, get)
}
if erlang {
external fn do_get(Map(key, value), key) -> Result(value, Nil) =
"gleam_stdlib" "map_get"
}
if javascript {
external fn do_get(Map(key, value), key) -> Result(value, Nil) =
"../gleam_stdlib.js" "map_get"
}
/// Inserts a value into the map with the given key.
///
/// If the map already has a value for the given key then the value is
/// replaced with the new value.
///
/// ## Examples
///
/// > new() |> insert("a", 0) |> to_list
/// [#("a", 0)]
///
/// > new() |> insert("a", 0) |> insert("a", 5) |> to_list
/// [#("a", 5)]
///
pub fn insert(into map: Map(k, v), for key: k, insert value: v) -> Map(k, v) {
do_insert(key, value, map)
}
if erlang {
external fn do_insert(key, value, Map(key, value)) -> Map(key, value) =
"maps" "put"
}
if javascript {
external fn do_insert(key, value, Map(key, value)) -> Map(key, value) =
"../gleam_stdlib.js" "map_insert"
}
/// Updates all values in a given map by calling a given function on each key
/// and value.
///
/// ## Examples
///
/// > [#(3, 3), #(2, 4)]
/// > |> from_list
/// > |> map_values(fn(key, value) { key * value })
/// [#(3, 9), #(2, 8)]
///
///
pub fn map_values(in map: Map(k, v), with fun: fn(k, v) -> w) -> Map(k, w) {
do_map_values(fun, map)
}
if erlang {
external fn do_map_values(fn(key, value) -> b, Map(key, value)) -> Map(key, b) =
"maps" "map"
}
if javascript {
fn do_map_values(f: fn(key, value) -> b, map: Map(key, value)) -> Map(key, b) {
let f = fn(map, k, v) { insert(map, k, f(k, v)) }
map
|> fold(from: new(), with: f)
}
}
/// Gets a list of all keys in a given map.
///
/// Maps are not ordered so the keys are not returned in any specific order. Do
/// not write code that relies on the order keys are returned by this function
/// as it may change in later versions of Gleam or Erlang.
///
/// ## Examples
///
/// > keys([#("a", 0), #("b", 1)])
/// ["a", "b"]
///
pub fn keys(map: Map(keys, v)) -> List(keys) {
do_keys(map)
}
if erlang {
external fn do_keys(Map(keys, v)) -> List(keys) =
"maps" "keys"
}
if javascript {
fn do_keys(map: Map(k, v)) -> List(k) {
map
|> to_list
|> list.map(pair.first)
}
}
/// Gets a list of all values in a given map.
///
/// Maps are not ordered so the values are not returned in any specific order. Do
/// not write code that relies on the order values are returned by this function
/// as it may change in later versions of Gleam or Erlang.
///
/// ## Examples
///
/// > keys(from_list([#("a", 0), #("b", 1)]))
/// [0, 1]
///
pub fn values(map: Map(k, values)) -> List(values) {
do_values(map)
}
if erlang {
external fn do_values(Map(k, values)) -> List(values) =
"maps" "values"
}
if javascript {
fn do_values(map: Map(k, v)) -> List(v) {
map
|> to_list
|> list.map(pair.second)
}
}
/// Creates a new map from a given map, minus any entries that a given function
/// returns False for.
///
/// ## Examples
///
/// > from_list([#("a", 0), #("b", 1)])
/// > |> filter(fn(key, value) { value != 0 })
/// from_list([#("b", 1)])
///
/// > from_list([#("a", 0), #("b", 1)])
/// > |> filter(fn(key, value) { True })
/// from_list([#("a", 0), #("b", 1)])
///
pub fn filter(in map: Map(k, v), for property: fn(k, v) -> Bool) -> Map(k, v) {
do_filter(property, map)
}
if erlang {
external fn do_filter(
fn(key, value) -> Bool,
Map(key, value),
) -> Map(key, value) =
"maps" "filter"
}
if javascript {
fn do_filter(
f: fn(key, value) -> Bool,
map: Map(key, value),
) -> Map(key, value) {
let insert = fn(map, k, v) {
case f(k, v) {
True -> insert(map, k, v)
_ -> map
}
}
map
|> fold(from: new(), with: insert)
}
}
/// Creates a new map from a given map, only including any entries for which the
/// keys are in a given list.
///
/// ## Examples
///
/// > from_list([#("a", 0), #("b", 1)])
/// > |> take(["b"])
/// from_list([#("b", 1)])
///
/// > from_list([#("a", 0), #("b", 1)])
/// > |> take(["a", "b", "c"])
/// from_list([#("a", 0), #("b", 1)])
///
pub fn take(from map: Map(k, v), keeping desired_keys: List(k)) -> Map(k, v) {
do_take(desired_keys, map)
}
if erlang {
external fn do_take(List(k), Map(k, v)) -> Map(k, v) =
"maps" "with"
}
if javascript {
fn do_take(desired_keys: List(k), map: Map(k, v)) -> Map(k, v) {
let insert = fn(taken, key) {
case get(map, key) {
Ok(value) -> insert(taken, key, value)
_ -> taken
}
}
list.fold(over: desired_keys, from: new(), with: insert)
}
}
/// Creates a new map from a pair of given maps by combining their entries.
///
/// If there are entries with the same keys in both maps the entry from the
/// second map takes precedence.
///
/// ## Examples
///
/// > let a = from_list([#("a", 0), #("b", 1)])
/// > let b = from_list([#("b", 2), #("c", 3)])
/// > merge(a, b)
/// from_list([#("a", 0), #("b", 2), #("c", 3)])
///
pub fn merge(into map: Map(k, v), from new_entries: Map(k, v)) -> Map(k, v) {
do_merge(map, new_entries)
}
if erlang {
external fn do_merge(Map(k, v), Map(k, v)) -> Map(k, v) =
"maps" "merge"
}
if javascript {
fn insert_pair(map: Map(k, v), pair: #(k, v)) -> Map(k, v) {
insert(map, pair.0, pair.1)
}
fn do_merge(map: Map(k, v), new_entries: Map(k, v)) -> Map(k, v) {
new_entries
|> to_list
|> list.fold(map, insert_pair)
}
}
/// Creates a new map from a given map with all the same entries except for the
/// one with a given key, if it exists.
///
/// ## Examples
///
/// > delete([#("a", 0), #("b", 1)], "a")
/// from_list([#("b", 1)])
///
/// > delete([#("a", 0), #("b", 1)], "c")
/// from_list([#("a", 0), #("b", 1)])
///
pub fn delete(from map: Map(k, v), delete key: k) -> Map(k, v) {
do_delete(key, map)
}
if erlang {
external fn do_delete(k, Map(k, v)) -> Map(k, v) =
"maps" "remove"
}
if javascript {
external fn do_delete(k, Map(k, v)) -> Map(k, v) =
"../gleam_stdlib.js" "map_remove"
}
/// Creates a new map from a given map with all the same entries except any with
/// keys found in a given list.
///
/// ## Examples
///
/// > drop([#("a", 0), #("b", 1)], ["a"])
/// from_list([#("b", 2)])
///
/// > delete([#("a", 0), #("b", 1)], ["c"])
/// from_list([#("a", 0), #("b", 1)])
///
/// > drop([#("a", 0), #("b", 1)], ["a", "b", "c"])
/// from_list([])
///
pub fn drop(from map: Map(k, v), drop disallowed_keys: List(k)) -> Map(k, v) {
list.fold(over: disallowed_keys, from: map, with: delete)
}
/// Creates a new map with one entry updated using a given function.
///
/// If there was not an entry in the map for the given key then the function
/// gets `Error(Nil)` as its argument, otherwise it gets `Ok(value)`.
///
/// ## Example
///
/// > let increment = fn(x) {
/// > case x {
/// > Ok(i) -> i + 1
/// > Error(Nil) -> 0
/// > }
/// > }
/// > let map = from_list([#("a", 0)])
/// >
/// > update(map, "a" increment)
/// from_list([#("a", 1)])
///
/// > update(map, "b" increment)
/// from_list([#("a", 0), #("b", 0)])
///
pub fn update(
in map: Map(k, v),
update key: k,
with fun: fn(Option(v)) -> v,
) -> Map(k, v) {
map
|> get(key)
|> option.from_result
|> fun
|> insert(map, key, _)
}
fn do_fold(list: List(#(k, v)), initial: acc, fun: fn(acc, k, v) -> acc) -> acc {
case list {
[] -> initial
[#(k, v), ..tail] -> do_fold(tail, fun(initial, k, v), fun)
}
}
/// Combines all entries into a single value by calling a given function on each
/// one.
///
/// Maps are not ordered so the values are not returned in any specific order. Do
/// not write code that relies on the order entries are used by this function
/// as it may change in later versions of Gleam or Erlang.
///
/// # Examples
///
/// > let map = from_list([#("a", 1), #("b", 3), #("c", 9)])
/// > fold(map, 0, fn(key, value, accumulator) { accumulator + value })
/// 13
///
/// > import gleam/string.{append}
/// > fold(map, "", fn(key, value, accumulator) { append(accumulator, value) })
/// "abc"
///
pub fn fold(
over map: Map(k, v),
from initial: acc,
with fun: fn(acc, k, v) -> acc,
) -> acc {
map
|> to_list
|> do_fold(initial, fun)
}