zip.ts

'use strict';

import { map } from './map';

function* _zip<T>(source: Iterable<T>[]): Iterable<T[]> {
  for (let i = 0; i < source.length; i++) {
    let its = source.map(x => x[Symbol.iterator]());
    let nexts = its.map(it => it.next());
    if (nexts.every(next => !next.done)) {
      yield nexts.map(next => next.value);
    }
  }
}

export function zip<T>(source: Iterable<T>, ...args: Iterable<T>[]): Iterable<T[]> {
  return _zip<T>([source].concat(...args));
}

export function zipStatic<T>(...args: Iterable<T>[]): Iterable<T[]> {
  return _zip<T>(args);
}

export function zipWith<T, TResult>(
    source: Iterable<T>,
    fn: (...args: T[]) => TResult,
    ...args: Iterable<T>[]): Iterable<TResult> {
  return map(_zip([source].concat(...args)), zipArgs => fn(...zipArgs));
}

export function zipWithStatic<T, TResult>(
    fn: (...args: T[]) => TResult,
    ...args: Iterable<T>[]): Iterable<TResult> {
  return map<T[], TResult>(_zip<T>(args), zipArgs => fn(...zipArgs));
}