SortedMap: keys in order¶

2 min read

SortedMap<K, V> keeps keys in their comparison order. Use it when you need the first, last, or nearest key as well as ordinary lookups. Keys must support Comparable<K>.

Import: import system.collections; · Availability: desktop, browser, and Node.

import system;
import system.collections;

fun main() {
    let scores = SortedMap<string, int>();
    scores["Sam"] = 80;
    scores["Ada"] = 95;
    for (let entry in scores) {
        System.println(entry.key);
    }
}

Output:

Ada
Sam

Read and change¶

set adds or replaces a value. get(key) returns Option<V>, while indexed reading requires the key to exist. contains, remove, clear, .length, and is_empty() cover common operations.

first_key() and last_key() return Option<K>. ceiling_key(key) finds the smallest key greater than or equal to the supplied key. floor_key(key) finds the largest key less than or equal to it. Both return None if no key qualifies.

keys() and values() return arrays in key order. Iteration produces key-value pairs in that same order.

Member	Returns	Effect
`SortedMap<K, V>(capacity = 8)`	`SortedMap<K, V>`	Empty map with room for `capacity` entries.
`map[key] = value`, `set(key, value)`	`void`	Adds the key or replaces its value.
`get(key)`	`Option<V>`	Value for `key`, or `None`.
`map[key]`	`V`	Value for `key`; a missing key stops the program.
`contains(key)`	`bool`	Whether `key` is present.
`remove(key)`	`bool`	Deletes the entry; `false` when the key was missing.
`clear()`	`void`	Deletes every entry and keeps capacity.
`.length`	`int`	Number of entries.
`is_empty()`	`bool`	`true` when there are no entries.
`first_key()`	`Option<K>`	Smallest key.
`last_key()`	`Option<K>`	Largest key.
`ceiling_key(key)`	`Option<K>`	Smallest key greater than or equal to `key`.
`floor_key(key)`	`Option<K>`	Largest key less than or equal to `key`.
`keys()`	`K[]`	New array of keys, smallest first.
`values()`	`V[]`	New array of values, in key order.

Lookups are fast, but adding or removing a key moves the entries after it. For large maps that change often and don't need ordering, a Map is faster. SortedMap is not a Collection, so the query helpers are not available on it; copy keys() or values() into a list first if you need them.

See all SortedMap signatures and Map for ordinary key lookup.