Maps

The map module defines the map type and all the map manipulation related functions.

A map is an associative container that can store heterogeneous types.

All the given examples assume the following imports:

let map = import('std/map');
let io = import('std/io');

Functions

map Member Functions

new

map.new(key1, value1, key2, value2, ...) -> map

Creates a new map using the given key/value pairs. The keys must be convertible to strings. Also, it must correspond a value to each key, meaning that the number of arguments must always be even

Example:

let m = map.new(0, "Zero", 1, "One", "Answer?", 42);
io.println(m);

Gives the output:

{Answer?: 42, 0: Zero, 1: One}

Note that the elements are not stored in any particular order and thus do not necessarily follow the given one

len

map.len() -> int

Returns the number of key/value pairs inside the map

Example:

io.println(map.new(0, "Zero", 1, "One", "Answer?", 42).len());

Gives the output:

3

insert

map.insert(key, value) -> map

Inserts the key/value pair and returns the modified map

Example:

let m = map.new(0, "Zero");
m.insert(1, "One");
io.println(m.insert("Answer?", 42));

Gives the output:

{Answer?: 42, 0: Zero, 1: One}

erase

map.erase(key) -> map

Removes the key and its associated value and returns the modified map

Example:

let m = map.new(0, "Zero", 1, "One", "Answer?", 42);
m.erase(1);
io.println(m.erase("Answer?"));

Gives the output:

{0: Zero}

get

map.get(key) -> map

Returns the value associated with key, or nil if it doesn't exist

Example:

let m = map.new(0, "Zero", 1, "One", "Answer?", 42);
io.println(m.get("Answer?"));
io.println(m.get("Oops"));

Gives the output:

42
(nil)

operator []

map[key] -> value

Returns the value associated with key, or nil if it doesn't exist

Example:

let m = map.new(0, "Zero", 1, "One", "Answer?", 42);
io.println(m["Answer?"]);
io.println(m["Oops"]);

Gives the output:

2
(nil)

each

map.each() -> iterator

Returns an iterator pointing to the first key/value pair, allowing easy map iteration

Example:

let m = map.new(0, "Zero", 1, "One", "Answer?", 42);
for elem in m.each() {
    io.println(elem.0, ": ", elem.1);
}

Gives the output:

Answer?: 42
0: Zero
1: One


iterator.next() -> value

Returns the key/value pair pointed by the iterator, or nil if out of range, and then advances the iterator to the next element

Example:

let m = map.new(0, "Zero", 1, "One", "Answer?", 42);
let iter = m.each();
for i in range(m.len()) {
    let elem = iter.next();
    io.println(elem.0, ': ', elem.1);
}

Gives the output:

Answer?: 42
0: Zero
1: One