Future fold(initialValue, dynamic combine(previous, T element))

Reduces a sequence of values by repeatedly applying combine.

Source 

Future/*<S>*/ fold/*<S>*/(var/*=S*/ initialValue,
    /*=S*/ combine(var/*=S*/ previous, T element)) {

  _Future/*<S>*/ result = new _Future/*<S>*/();
  var/*=S*/ value = initialValue;
  StreamSubscription subscription;
  subscription = this.listen(
    (T element) {
      _runUserCode(
        () => combine(value, element),
        (/*=S*/ newValue) { value = newValue; },
        _cancelAndErrorClosure(subscription, result)
      );
    },
    onError: (e, st) {
      result._completeError(e, st);
    },
    onDone: () {
      result._complete(value);
    },
    cancelOnError: true);
  return result;
}