543 lines
12 KiB
TypeScript
543 lines
12 KiB
TypeScript
/**
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* Empty iterator
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*/
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export const IATEND: Iterator<any> = {
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next: function () {
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return { done: true, value: undefined };
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},
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};
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/**
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* Empty iterable
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*/
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export const IEMPTY: Iterable<any> = {
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[Symbol.iterator]: () => IATEND,
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};
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/**
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* Iterable constructor, from an initial value, and a step value
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*/
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export function irecur<T, S>(start: T, step: (a: T) => T | null): Iterable<T> {
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return {
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[Symbol.iterator]: function* () {
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let val: T | null = start;
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do {
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yield val;
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val = step(val);
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} while (val !== null);
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},
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};
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}
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/**
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* Iterable constructor, from an array
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*
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* The iterator will yield the next value each time it is called, then undefined when the array's end is reached.
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*/
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export function iarray<T>(array: T[], offset = 0): Iterable<T> {
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return {
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[Symbol.iterator]: function () {
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return array.slice(offset)[Symbol.iterator]();
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},
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};
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}
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/**
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* Iterable constructor, from a single value
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*
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* The value will be yielded only once, not repeated over.
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*/
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export function isingle<T>(value: T): Iterable<T> {
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return iarray([value]);
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}
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/**
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* Iterable that repeats the same value.
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*/
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export function irepeat<T>(value: T, count = -1): Iterable<T> {
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return {
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[Symbol.iterator]: function* () {
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let n = count;
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while (n != 0) {
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yield value;
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n--;
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}
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},
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};
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}
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/**
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* Equivalent of Array.forEach for all iterables.
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*
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* If the callback returns *stopper*, the iteration is stopped.
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*/
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export function iforeach<T>(
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iterable: Iterable<T>,
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callback: (_: T) => any,
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stopper: any = null,
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): void {
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for (let value of iterable) {
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if (callback(value) === stopper) {
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break;
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}
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}
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}
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/**
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* Returns the first item passing a predicate
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*/
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export function ifirst<T>(
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iterable: Iterable<T>,
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predicate: (item: T) => boolean,
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): T | null {
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for (let value of iterable) {
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if (predicate(value)) {
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return value;
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}
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}
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return null;
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}
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/**
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* Returns the first non-null result of a value-yielding predicate, applied to each iterator element
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*/
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export function ifirstmap<T1, T2>(
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iterable: Iterable<T1>,
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predicate: (item: T1) => T2 | null,
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): T2 | null {
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for (let value of iterable) {
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let res = predicate(value);
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if (res !== null) {
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return res;
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}
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}
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return null;
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}
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/**
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* Materialize an array from consuming an iterable
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*
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* To avoid materializing infinite iterators (and bursting memory), the item count is limited to 1 million, and an
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* exception is thrown when this limit is reached.
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*/
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export function imaterialize<T>(iterable: Iterable<T>, limit = 1000000): T[] {
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let result: T[] = [];
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for (let value of iterable) {
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result.push(value);
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if (result.length >= limit) {
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throw new Error("Length limit on iterator materialize");
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}
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}
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return result;
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}
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/**
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* Count items in an iterator
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*
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* To avoid counting infinite iterators (and bursting memory), the item count is limited by
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* the *limit* parameter, and Infinity will be returned after that many.
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*/
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export function ilength<T>(iterable: Iterable<T>, limit = 1000000): number {
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let result = 0;
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for (let _ of iterable) {
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if (result >= limit) {
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return Infinity;
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}
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result += 1;
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}
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return result;
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}
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/**
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* Iterate over natural integers
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*
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* If *count* is not specified, the iterator is infinite
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*/
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export function irange(
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count: number = -1,
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start = 0,
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step = 1,
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): Iterable<number> {
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return {
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[Symbol.iterator]: function* () {
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let i = start;
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let n = count;
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while (n != 0) {
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yield i;
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i += step;
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n--;
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}
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},
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};
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}
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/**
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* Iterate over numbers, by applying a step taken from an other iterator
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*
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* This iterator stops when the "step iterator" stops
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*
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* With no argument, istep() == irange()
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*/
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export function istep(start = 0, step_iterable = irepeat(1)): Iterable<number> {
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return {
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[Symbol.iterator]: function* () {
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let i = start;
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yield i;
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for (let step of step_iterable) {
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i += step;
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yield i;
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}
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},
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};
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}
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/**
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* Skip a given number of values from an iterator, discarding them.
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*/
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export function iskip<T>(iterable: Iterable<T>, count = 1): Iterable<T> {
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return {
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[Symbol.iterator]: function () {
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let iterator = iterable[Symbol.iterator]();
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let n = count;
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while (n-- > 0) {
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iterator.next();
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}
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return iterator;
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},
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};
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}
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/**
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* Return the value at a given position in the iterator
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*/
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export function iat<T>(iterable: Iterable<T>, position: number): T | null {
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if (position < 0) {
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return null;
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} else {
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if (position > 0) {
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iterable = iskip(iterable, position);
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}
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let iterator = iterable[Symbol.iterator]();
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let state = iterator.next();
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return state.done ? null : state.value;
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}
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}
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/**
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* Chain an iterable of iterables.
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*
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* This will yield values from the first yielded iterator, then the second one, and so on...
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*/
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export function ichainit<T>(iterables: Iterable<Iterable<T>>): Iterable<T> {
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return {
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[Symbol.iterator]: function* () {
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for (let iterable of iterables) {
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for (let value of iterable) {
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yield value;
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}
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}
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},
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};
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}
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/**
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* Chain iterables.
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*
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* This will yield values from the first iterator, then the second one, and so on...
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*/
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export function ichain<T>(...iterables: Iterable<T>[]): Iterable<T> {
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if (iterables.length == 0) {
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return IEMPTY;
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} else {
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return ichainit(iterables);
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}
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}
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/**
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* Loop an iterator for a number of times.
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*
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* If count is negative, if will loop forever (infinite iterator).
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*
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* onloop may be used to know when the iterator resets.
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*/
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export function iloop<T>(
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base: Iterable<T>,
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count = -1,
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onloop?: Function,
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): Iterable<T> {
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return {
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[Symbol.iterator]: function* () {
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let n = count;
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let start = false;
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while (n-- != 0) {
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for (let value of base) {
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if (start) {
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if (onloop) {
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onloop();
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}
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start = false;
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}
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yield value;
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}
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start = true;
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}
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},
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};
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}
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/**
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* Iterator version of "map".
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*/
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export function imap<T1, T2>(
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iterable: Iterable<T1>,
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mapfunc: (_: T1) => T2,
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): Iterable<T2> {
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return {
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[Symbol.iterator]: function* () {
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for (let value of iterable) {
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yield mapfunc(value);
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}
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},
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};
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}
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/**
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* Iterator version of "reduce".
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*/
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export function ireduce<T>(
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iterable: Iterable<T>,
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reduce: (item1: T, item2: T) => T,
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init: T,
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): T {
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let result = init;
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for (let value of iterable) {
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result = reduce(result, value);
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}
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return result;
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}
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/**
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* Iterator version of "filter".
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*/
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export function ifilter<T>(
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iterable: Iterable<T>,
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filterfunc: (_: T) => boolean,
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): Iterable<T> {
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return {
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[Symbol.iterator]: function* () {
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for (let value of iterable) {
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if (filterfunc(value)) {
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yield value;
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}
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}
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},
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};
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}
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/**
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* Apply map, and filter invalid results in the same pass.
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*/
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export function imapfilter<T1, T2>(
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iterable: Iterable<T1>,
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mapfunc: (_: T1) => T2 | null,
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): Iterable<Exclude<T2, null>> {
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return {
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[Symbol.iterator]: function* () {
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for (let value of iterable) {
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const mapped = mapfunc(value);
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if (mapped !== null) {
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yield mapped as Exclude<T2, null>;
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}
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}
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},
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};
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}
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/**
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* Type filter, to return a list of instances of a given type
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*/
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export function ifiltertype<T>(
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iterable: Iterable<any>,
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filter: (item: any) => item is T,
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): Iterable<T> {
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return ifilter(iterable, filter);
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}
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/**
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* Class filter, to return a list of instances of a given type
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*/
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export function ifilterclass<T>(
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iterable: Iterable<any>,
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classref: { new (...args: any[]): T },
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): Iterable<T> {
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return ifilter(iterable, (item): item is T => item instanceof classref);
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}
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/**
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* Combine two iterables.
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*
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* This iterates through the second one several times, so if one iterator may be infinite,
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* it should be the first one.
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*/
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export function icombine<T1, T2>(
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it1: Iterable<T1>,
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it2: Iterable<T2>,
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): Iterable<[T1, T2]> {
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return ichainit(imap(it1, (v1) => imap(it2, (v2): [T1, T2] => [v1, v2])));
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}
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/**
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* Advance through two iterables at the same time, yielding item pairs
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*
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* Iteration will stop at the first of the two iterators that stops.
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*/
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export function izip<T1, T2>(
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it1: Iterable<T1>,
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it2: Iterable<T2>,
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): Iterable<[T1, T2]> {
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return {
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[Symbol.iterator]: function* () {
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let iterator1 = it1[Symbol.iterator]();
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let iterator2 = it2[Symbol.iterator]();
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let state1 = iterator1.next();
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let state2 = iterator2.next();
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while (!state1.done && !state2.done) {
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yield [state1.value, state2.value];
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state1 = iterator1.next();
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state2 = iterator2.next();
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}
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},
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};
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}
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/**
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* Advance two iterables at the same time, yielding item pairs (greedy version)
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*
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* Iteration will stop when both iterators are consumed, returning partial couples (undefined in the peer) if needed.
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*/
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export function izipg<T1, T2>(
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it1: Iterable<T1>,
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it2: Iterable<T2>,
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): Iterable<[T1 | undefined, T2 | undefined]> {
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return {
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[Symbol.iterator]: function* () {
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let iterator1 = it1[Symbol.iterator]();
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let iterator2 = it2[Symbol.iterator]();
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let state1 = iterator1.next();
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let state2 = iterator2.next();
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while (!state1.done || !state2.done) {
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yield [state1.value, state2.value];
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state1 = iterator1.next();
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state2 = iterator2.next();
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}
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},
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};
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}
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/**
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* Partition in two iterables, one with values that pass the predicate, the other with values that don't
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*/
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export function ipartition<T>(
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iterable: Iterable<T>,
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predicate: (item: T) => boolean,
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): [Iterable<T>, Iterable<T>] {
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return [
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ifilter(iterable, predicate),
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ifilter(iterable, (x) => !predicate(x)),
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];
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}
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/**
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* Alternate between several iterables (pick one from the first one, then one from the second...)
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*/
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export function ialternate<T>(iterables: Iterable<T>[]): Iterable<T> {
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return {
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[Symbol.iterator]: function* () {
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let iterators = iterables.map((iterable) => iterable[Symbol.iterator]());
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let done: boolean;
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do {
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done = false;
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// TODO Remove "dried-out" iterators
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for (let iterator of iterators) {
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let state = iterator.next();
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if (!state.done) {
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done = true;
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yield state.value;
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}
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}
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} while (done);
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},
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};
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}
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/**
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* Yield items from an iterator only once.
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*
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* Beware that even if this function is not materializing, it keeps track of yielded item, and may choke on
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* infinite or very long streams. Thus, no more than *limit* items will be yielded (an error is thrown
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* when this limit is reached).
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*
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* This function is O(n²)
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*/
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export function iunique<T>(
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iterable: Iterable<T>,
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limit = 1000000,
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): Iterable<T> {
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return {
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[Symbol.iterator]: function* () {
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let done: Set<T> = new Set();
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let n = limit;
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for (let value of iterable) {
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if (!done.has(value)) {
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if (n-- > 0) {
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done.add(value);
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yield value;
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} else {
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throw new Error("Unique count limit on iterator");
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}
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}
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}
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},
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};
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}
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/**
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* Common reduce shortcuts
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*/
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export const isum = (iterable: Iterable<number>) =>
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ireduce(iterable, (a, b) => a + b, 0);
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export const icat = (iterable: Iterable<string>) =>
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ireduce(iterable, (a, b) => a + b, "");
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export const imin = (iterable: Iterable<number>) =>
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ireduce(iterable, Math.min, Infinity);
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export const imax = (iterable: Iterable<number>) =>
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ireduce(iterable, Math.max, -Infinity);
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/**
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* Min/max by key function
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*/
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export function iminBy<T>(
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iterable: Iterable<T>,
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key: (value: T) => number,
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): T | undefined {
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return ireduce(
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iterable,
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(item1, item2) =>
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(typeof item1 == "undefined" || typeof item2 == "undefined") ||
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(key(item1) > key(item2))
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? item2
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: item1,
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undefined,
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);
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}
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export function imaxBy<T>(
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iterable: Iterable<T>,
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key: (value: T) => number,
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): T | undefined {
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return iminBy(iterable, (value) => -key(value));
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}
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