import { DistinctEqualFn } from "../operations/sync/distinct";
export interface Retainer<T> extends Iterable<T> {
    has?(value: T): boolean;
    add(value: T): void;
}
export interface RetainerWithHas<T> extends Retainer<T> {
    has(value: T): boolean;
}
export declare function arrayRetainer<T>(has?: (value: T, values: T[]) => boolean): Retainer<T>;
export declare function setRetainer<T>(): RetainerWithHas<T>;
export declare function distinctRetainer<T>(equalityFn?: DistinctEqualFn<T>): RetainerWithHas<T>;
export declare function retain<T>(iterable: Iterable<T>, retainer?: Retainer<T>): Iterable<T>;