import type { IEnumerable, IEqualityComparer, IGrouping, SelectorKeyType } from "../../types";
type GroupByFunc = {
    <TSource, TKey extends SelectorKeyType>(source: Iterable<TSource>, keySelector: (x: TSource) => TKey): IEnumerable<IGrouping<TKey, TSource>>;
    <TSource, TKey>(source: Iterable<TSource>, keySelector: (x: TSource) => TKey, comparer: IEqualityComparer<TKey>): IEnumerable<IGrouping<TKey, TSource>>;
};
export declare const groupBy: GroupByFunc;
export {};