hunk.code_window:  * @param {function(value: T, ?index: number): ObservableInput} project A function
    * that, when applied to an item emitted by the source Observable, returns an
    * Observable.
    * @return {Observable} An Observable that emits the result of applying the
    * projection function (and the optional `resultSelector`) to each item emitted
    * by the source Observable and taking values from each projected inner
    * Observable sequentially.
    * @method concatMap
    * @owner Observable
  
hunk.labels: keep keep keep keep replace keep keep keep keep
hunk.after_edit:  * projection function (and the optional deprecated `resultSelector`) to each item emitted
  
hunk.file_path: src/internal/operators/concatMap.ts
hunk.type: replace
file: import { mergeMap } from './mergeMap';
  import { ObservableInput, OperatorFunction } from '../types';
  
  /* tslint:disable:max-line-length */
  export function concatMap<T, R>(project: (value: T, index: number) =>  ObservableInput<R>): OperatorFunction<T, R>;
  /** @deprecated resultSelector no longer supported, use inner map instead */
  export function concatMap<T, R>(project: (value: T, index: number) => ObservableInput<R>, resultSelector: undefined): OperatorFunction<T, R>;
  /** @deprecated resultSelector no longer supported, use inner map instead */
  export function concatMap<T, I, R>(project: (value: T, index: number) =>  ObservableInput<I>, resultSelector: (outerValue: T, innerValue: I, outerIndex: number, innerIndex: number) => R): OperatorFunction<T, R>;
  /* tslint:enable:max-line-length */
  
  /**
   * Projects each source value to an Observable which is merged in the output
   * Observable, in a serialized fashion waiting for each one to complete before
   * merging the next.
   *
   * <span class="informal">Maps each value to an Observable, then flattens all of
   * these inner Observables using {@link concatAll}.</span>
   *
   * ![](concatMap.png)
   *
   * Returns an Observable that emits items based on applying a function that you
   * supply to each item emitted by the source Observable, where that function
   * returns an (so-called "inner") Observable. Each new inner Observable is
   * concatenated with the previous inner Observable.
   *
   * __Warning:__ if source values arrive endlessly and faster than their
   * corresponding inner Observables can complete, it will result in memory issues
   * as inner Observables amass in an unbounded buffer waiting for their turn to
   * be subscribed to.
   *
   * Note: `concatMap` is equivalent to `mergeMap` with concurrency parameter set
   * to `1`.
   *
   * ## Example
   * For each click event, tick every second from 0 to 3, with no concurrency
   *
   * ```javascript
   * const clicks = fromEvent(document, 'click');
   * const result = clicks.pipe(
   *   concatMap(ev => interval(1000).pipe(take(4)),
   * );
   * result.subscribe(x => console.log(x));
   *
   * // Results in the following:
   * // (results are not concurrent)
   * // For every click on the "document" it will emit values 0 to 3 spaced
   * // on a 1000ms interval
   * // one click = 1000ms-> 0 -1000ms-> 1 -1000ms-> 2 -1000ms-> 3
   * ```
   *
   * @see {@link concat}
   * @see {@link concatAll}
   * @see {@link concatMapTo}
   * @see {@link exhaustMap}
   * @see {@link mergeMap}
   * @see {@link switchMap}
   *
   * @param {function(value: T, ?index: number): ObservableInput} project A function
   * that, when applied to an item emitted by the source Observable, returns an
   * Observable.
   * @return {Observable} An Observable that emits the result of applying the
   * projection function (and the optional `resultSelector`) to each item emitted
   * by the source Observable and taking values from each projected inner
   * Observable sequentially.
   * @method concatMap
   * @owner Observable
   */
  export function concatMap<T, I, R>(
    project: (value: T, index: number) =>  ObservableInput<I>,
    resultSelector?: (outerValue: T, innerValue: I, outerIndex: number, innerIndex: number) => R
  ): OperatorFunction<T, I|R> {
    return mergeMap(project, resultSelector, 1);
  }
  