78 lines
1.9 KiB
TypeScript
78 lines
1.9 KiB
TypeScript
// Bags and Deltas (which are Bags where item-counts can be negative).
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import { Value, Set, Dictionary, DefaultPointer } from '@preserves/core';
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export enum ChangeDescription {
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PRESENT_TO_ABSENT = -1,
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ABSENT_TO_ABSENT = 0,
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ABSENT_TO_PRESENT = 1,
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PRESENT_TO_PRESENT = 2,
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}
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export class Bag<T extends object = DefaultPointer> {
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_items: Dictionary<T, number>;
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constructor(s?: Set<T>) {
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this._items = new Dictionary();
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if (s) s.forEach((v) => this._items.set(v, 1));
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}
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get(key: Value<T>): number {
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return this._items.get(key, 0) as number;
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}
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change(key: Value<T>, delta: number, clamp: boolean = false): ChangeDescription {
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let oldCount = this.get(key);
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let newCount = oldCount + delta;
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if (clamp) {
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newCount = Math.max(0, newCount);
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}
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if (newCount === 0) {
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this._items.delete(key);
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return (oldCount === 0)
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? ChangeDescription.ABSENT_TO_ABSENT
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: ChangeDescription.PRESENT_TO_ABSENT;
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} else {
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this._items.set(key, newCount);
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return (oldCount === 0)
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? ChangeDescription.ABSENT_TO_PRESENT
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: ChangeDescription.PRESENT_TO_PRESENT;
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}
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}
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clear() {
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this._items = new Dictionary();
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}
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includes(key: Value<T>): boolean {
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return this._items.has(key);
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}
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get size(): number {
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return this._items.size;
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}
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keys(): IterableIterator<Value<T>> {
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return this._items.keys();
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}
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entries(): IterableIterator<[Value<T>, number]> {
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return this._items.entries();
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}
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forEach(f: (count: number, value: Value<T>) => void) {
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this._items.forEach(f);
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}
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snapshot(): Dictionary<T, number> {
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return this._items.clone();
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}
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clone(): Bag<T> {
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const b = new Bag<T>();
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b._items = this._items.clone();
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return b;
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}
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}
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