/**
 * Represents an immutable set that works best for a small number of elements (less than 32).
 * It uses bits to encode element membership efficiently.
*/
export declare class SmallImmutableSet<T> {
    private readonly items;
    private readonly additionalItems;
    private static cache;
    private static create;
    private static empty;
    static getEmpty<T>(): SmallImmutableSet<T>;
    private constructor();
    add(value: T, keyProvider: IDenseKeyProvider<T>): SmallImmutableSet<T>;
    has(value: T, keyProvider: IDenseKeyProvider<T>): boolean;
    merge(other: SmallImmutableSet<T>): SmallImmutableSet<T>;
    intersects(other: SmallImmutableSet<T>): boolean;
    equals(other: SmallImmutableSet<T>): boolean;
}
export interface IDenseKeyProvider<T> {
    getKey(value: T): number;
}
export declare const identityKeyProvider: IDenseKeyProvider<number>;
/**
 * Assigns values a unique incrementing key.
*/
export declare class DenseKeyProvider<T> {
    private readonly items;
    getKey(value: T): number;
    reverseLookup(value: number): T | undefined;
    reverseLookupSet(set: SmallImmutableSet<T>): T[];
    keys(): IterableIterator<T>;
}