import { AsyncIterableX } from '../asynciterablex';
/**
 * @ignore
 */
export declare function defaultCompareAsync<T>(key: T, minValue: T): Promise<number>;
/**
 * @ignore
 */
export declare function extremaBy<TSource, TKey>(source: AsyncIterable<TSource>, keyFn: (x: TSource) => TKey | Promise<TKey>, cmp: (x: TKey, y: TKey) => number | Promise<number>): AsyncIterableX<TSource>;