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zena:ordered-map

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import {…} from 'zena:ordered-map';

Classes

OrderedMap

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final class OrderedMap<K extends Hashable, V> extends HashMap<K, V>
Extends HashMap<K, V>
Re-exported from zena:collections/hash-map.zena

A hash map that iterates in insertion order — exported as OrderedHashMap.

Order is maintained by a doubly-linked list through the entries, so it costs two pointers per entry and nothing per lookup. Replacing an existing key's value keeps its position; deleting a key and inserting it again moves it to the end.

Iteration follows the same rules as JavaScript's Map:

  • entries inserted during an iteration are visited by it;
  • entries deleted before an iteration reaches them are not visited;
  • deleting the entry an iteration is parked on does not disturb it;
  • once an iterator reports exhaustion it stays exhausted.

Example: let m = new OrderedHashMap<String, i32>(); m["b"] = 2; m["a"] = 1; // Iteration order: "b", "a"

Constructors
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new(capacity: i32 = 16)
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Methods
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clear(): void
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Removes every entry.

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keys(): Iterator<K>
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Returns an iterator over the keys, in insertion order.

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forEach(callback: (key: K, value: V) => void): void
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Calls callback once per entry, in insertion order, under the same rules as iteration.

14 inherited members
From HashMap
Properties
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size: i32 { get; }
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Methods
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get(key: K): inline (true, V) | inline (false, _)
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(true, value) if the key is present, (false, _) otherwise. An inline tuple, so this is the allocation-free way to test and read in one step.

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getOr(key: K, defaultValue: V): V
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The value for key, or defaultValue if the key is absent.

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getOption(key: K): Option<V>
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Some(value) if the key is present, None otherwise. Prefer get unless the result has to be stored or passed on.

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has(key: K): boolean
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delete(key: K): boolean
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Removes key. Returns whether it was present.

Operators
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operator []=(key: K, value: V): void
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operator [](key: K): V
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The value for key. Throws KeyNotFoundError if the key is absent.

From Iterable
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contains(value: T): boolean
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Returns true if the collection contains the specified value.

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all(predicate: (item: T) => boolean): boolean
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Returns true if all elements match the given predicate. Returns true if the collection is empty.

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some(predicate: (item: T) => boolean): boolean
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Returns true if at least one element matches the given predicate. Returns false if the collection is empty.

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fold<R>(initial: R, combine: (acc: R, item: T) => R): R
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Reduces the collection to a single value by accumulating state.

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find(predicate: (item: T) => boolean): inline (true, T) | inline (false, _)
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Finds the first element that matches the predicate. Returns an inline tuple (true, item) if found, or (false, _) if not.

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filter(predicate: (item: T) => boolean): Iterable<T>
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Returns a new iterable containing only the elements that match the predicate.