import type * as GB from "../../GroupBy";
import type * as C from "../core";
/**
 * Partition a stream using a function and process each stream individually.
 * This returns a data structure that can be used
 * to further filter down which groups shall be processed.
 *
 * After calling apply on the GroupBy object, the remaining groups will be processed
 * in parallel and the resulting streams merged in a nondeterministic fashion.
 *
 * Up to `buffer` elements may be buffered in any group stream before the producer
 * is backpressured. Take care to consume from all streams in order
 * to prevent deadlocks.

 */
export declare function groupByKey_<R, E, A, K>(self: C.Stream<R, E, A>, f: (a: A) => K, buffer?: number): GB.GroupBy<R, E, K, A, A>;
/**
 * Partition a stream using a function and process each stream individually.
 * This returns a data structure that can be used
 * to further filter down which groups shall be processed.
 *
 * After calling apply on the GroupBy object, the remaining groups will be processed
 * in parallel and the resulting streams merged in a nondeterministic fashion.
 *
 * Up to `buffer` elements may be buffered in any group stream before the producer
 * is backpressured. Take care to consume from all streams in order
 * to prevent deadlocks.
 *
 * @ets_data_first groupByKey_
 */
export declare function groupByKey<A, K>(f: (a: A) => K, buffer?: number): <R, E>(self: C.Stream<R, E, A>) => GB.GroupBy<R, E, K, A, A>;
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