import { IterableX } from '../iterable';
/**
 * @ignore
 */
export declare function defaultCompare<T>(key: T, minValue: T): number;
/**
 * @ignore
 */
export declare function extremaBy<TSource, TKey>(source: Iterable<TSource>, keyFn: (x: TSource) => TKey, cmp: (x: TKey, y: TKey) => number): IterableX<TSource>;