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111 lines
3.5 KiB
TypeScript
111 lines
3.5 KiB
TypeScript
/**
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* Copyright (c) 2021 OpenLens Authors
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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/**
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* Create a new type safe empty Iterable
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* @returns An `Iterable` that yields 0 items
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*/
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export function* newEmpty<T>(): Iterable<T> {
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return;
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}
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/**
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* Creates a new `Iterable` that yields at most n items from src.
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* Does not modify `src` which can be used later.
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* @param src An initial iterator
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* @param n The maximum number of elements to take from src. Yields up to the floor of `n` and 0 items if n < 0
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*/
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export function* take<T>(src: Iterable<T>, n: number): Iterable<T> {
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outer: for (let i = 0; i < n; i += 1) {
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for (const item of src) {
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yield item;
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continue outer;
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}
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// if we are here that means that `src` has been exhausted. Don't bother trying again.
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break outer;
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}
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}
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/**
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* Creates a new iterator that iterates (lazily) over its input and yields the
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* result of `fn` for each item.
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* @param src A type that can be iterated over
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* @param fn The function that is called for each value
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*/
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export function* map<T, U>(src: Iterable<T>, fn: (from: T) => U): Iterable<U> {
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for (const from of src) {
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yield fn(from);
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}
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}
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export function* flatMap<T, U>(src: Iterable<T>, fn: (from: T) => Iterable<U>): Iterable<U> {
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for (const from of src) {
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yield* fn(from);
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}
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}
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/**
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* Creates a new iterator that iterates (lazily) over its input and yields the
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* items that return a `truthy` value from `fn`.
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* @param src A type that can be iterated over
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* @param fn The function that is called for each value
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*/
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export function* filter<T>(src: Iterable<T>, fn: (from: T) => any): Iterable<T> {
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for (const from of src) {
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if (fn(from)) {
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yield from;
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}
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}
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}
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/**
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* Creates a new iterator that iterates (lazily) over its input and yields the
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* result of `fn` when it is `truthy`
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* @param src A type that can be iterated over
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* @param fn The function that is called for each value
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*/
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export function* filterMap<T, U>(src: Iterable<T>, fn: (from: T) => U): Iterable<U> {
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for (const from of src) {
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const res = fn(from);
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if (res) {
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yield res;
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}
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}
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}
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/**
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* Creates a new iterator that iterates (lazily) over its input and yields the
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* result of `fn` when it is not null or undefined
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* @param src A type that can be iterated over
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* @param fn The function that is called for each value
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*/
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export function* filterMapStrict<T, U>(src: Iterable<T>, fn: (from: T) => U): Iterable<U> {
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for (const from of src) {
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const res = fn(from);
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if (res != null) {
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yield res;
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}
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}
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}
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