aggregateRightSelect<TResult> method

TResult aggregateRightSelect<TResult>(TResult initialValue, TResult aggregator(TResult aggregate, T element))

Aggregates the iterable into a single value in a right-associative manner.

Aggregates the source iterable by applying the aggregator function to each value in the collection in the order they appear, starting from the last element and working backwards. The result is a single value that is the result of the aggregation.

The aggregator function offers two parameters - the accumulator and the value. In each iteration, the accumulator represents the running result of the aggregation and the value represents the current element to process. The function should return what the next value of the aggregation should be, and that value will become the accumulator on the next iteration. Once the aggregation is complete, the last value to be returned is considered the result of the aggregation process.

The initialValue parameter determines the starting value of the aggregation and will be the first value passed as the accumulator parameter. If the iterable is empty, initialValue will be returned.

Example:

void main() {
  final list = ['a', 'b', 'c'];
  final result = list.aggregate('d', (prev, elem) => '($elem, $prev)');

  // Result: (a, (b, (c, d)))
}

Implementation

TResult aggregateRightSelect<TResult>(
  TResult initialValue,
  TResult Function(TResult aggregate, T element) aggregator,
) {
  final stack = Queue<T>();
  for (var obj in this) {
    stack.add(obj);
  }

  if (stack.isEmpty) {
    return initialValue;
  }

  var value = initialValue;
  if (stack.isEmpty) {
    return value;
  }

  while (stack.isNotEmpty) {
    value = aggregator(value, stack.removeLast());
  }

  return value;
}