pnpm/lib/node_modules/most/src/combinator/flatMap.js

Fast, disk space efficient package manager

/** @license MIT License (c) copyright 2010-2016 original author or authors */
/** @author Brian Cavalier */
/** @author John Hann */

import { mergeConcurrently, mergeMapConcurrently } from './mergeConcurrently'

/**
 * Map each value in the stream to a new stream, and merge it into the
 * returned outer stream. Event arrival times are preserved.
 * @param {function(x:*):Stream} f chaining function, must return a Stream
 * @param {Stream} stream
 * @returns {Stream} new stream containing all events from each stream returned by f
 */
export function flatMap (f, stream) {
  return mergeMapConcurrently(f, Infinity, stream)
}

/**
 * Monadic join. Flatten a Stream<Stream<X>> to Stream<X> by merging inner
 * streams to the outer. Event arrival times are preserved.
 * @param {Stream<Stream<X>>} stream stream of streams
 * @returns {Stream<X>} new stream containing all events of all inner streams
 */
export function join (stream) {
  return mergeConcurrently(Infinity, stream)
}