import { EqualityComparer, ResultSelector } from '../types';
import type { IEnumerable } from './enumerable.interface';
export interface ILookup<TKey, TElement> {
}
export declare class Lookup<TKey, TElement> implements ILookup<TKey, TElement> {
    private _comparer;
    private _groupings;
    constructor(comparer?: EqualityComparer<TKey>);
    static create<TKey, TSource, TElement = TSource>(source: IEnumerable<TSource>, keySelector: ResultSelector<TSource, TKey>, elementSelector?: ResultSelector<TSource, TElement> | null, comparer?: EqualityComparer<TKey>): Lookup<TKey, TElement>;
    getGroups(): IGrouping<TKey, TElement>[];
    getGroupElements(key: TKey): IEnumerable<TElement>;
    getGrouping(key: TKey, create?: boolean): Grouping<TKey, TElement> | null;
}
export interface IGrouping<TKey, TElement> {
    key: TKey;
    elements: IEnumerable<TElement>;
}
export declare class Grouping<TKey, TElement> implements IGrouping<TKey, TElement> {
    readonly key: TKey;
    readonly elements: TElement[];
    get count(): number;
    constructor(key: TKey, elements?: TElement[]);
    atIndex(idx: number): TElement;
    add(element: TElement): void;
}