text: /** PURE_IMPORTS_START .._operators_reduce PURE_IMPORTS_END */
  import { reduce as higherOrderReduce } from '../operators/reduce';
  /* tslint:enable:max-line-length */
  /**
   * Applies an accumulator function over the source Observable, and returns the
   * accumulated result when the source completes, given an optional seed value.
   *
   * <span class="informal">Combines together all values emitted on the source,
   * using an accumulator function that knows how to join a new source value into
   * the accumulation from the past.</span>
   *
   * <img src="./img/reduce.png" width="100%">
   *
   * Like
   * [Array.prototype.reduce()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce),
   * `reduce` applies an `accumulator` function against an accumulation and each
   * value of the source Observable (from the past) to reduce it to a single
   * value, emitted on the output Observable. Note that `reduce` will only emit
   * one value, only when the source Observable completes. It is equivalent to
   * applying operator {@link scan} followed by operator {@link last}.
   *
   * Returns an Observable that applies a specified `accumulator` function to each
   * item emitted by the source Observable. If a `seed` value is specified, then
   * that value will be used as the initial value for the accumulator. If no seed
   * value is specified, the first item of the source is used as the seed.
   *
   * @example <caption>Count the number of click events that happened in 5 seconds</caption>
   * var clicksInFiveSeconds = Rx.Observable.fromEvent(document, 'click')
   *   .takeUntil(Rx.Observable.interval(5000));
   * var ones = clicksInFiveSeconds.mapTo(1);
   * var seed = 0;
   * var count = ones.reduce((acc, one) => acc + one, seed);
   * count.subscribe(x => console.log(x));
   *
   * @see {@link count}
   * @see {@link expand}
   * @see {@link mergeScan}
   * @see {@link scan}
   *
   * @param {function(acc: R, value: T, index: number): R} accumulator The accumulator function
   * called on each source value.
   * @param {R} [seed] The initial accumulation value.
   * @return {Observable<R>} An Observable that emits a single value that is the
   * result of accumulating the values emitted by the source Observable.
   * @method reduce
   * @owner Observable
   */
  export function reduce(accumulator, seed) {
      // providing a seed of `undefined` *should* be valid and trigger
      // hasSeed! so don't use `seed !== undefined` checks!
      // For this reason, we have to check it here at the original call site
      // otherwise inside Operator/Subscriber we won't know if `undefined`
      // means they didn't provide anything or if they literally provided `undefined`
      if (arguments.length >= 2) {
          return higherOrderReduce(accumulator, seed)(this);
      }
      return higherOrderReduce(accumulator)(this);
  }
  //# sourceMappingURL=reduce.js.map
  