fold
inline fun <T, K, R> Grouping<T, K>.fold(
initialValueSelector: (key: K, element: T) -> R,
operation: (key: K, accumulator: R, element: T) -> R
): Map<K, R>
Platform and version requirements: Kotlin 1.1
Groups elements from the Grouping source by key and applies 登录查看完整内容
