import { Observable } from "rxjs";
/**
 * Operator that caches a source observable, and refresh it when it expires.
 * Refreshing occurs on subscription (as opposed to on a timer).
 *
 * @param timeout Flush the cache after having no subscribers for this duration
 * (milliseconds).
 *
 * Example:
 *
 * ```ts
 * apiService.fetchExpiringUrl.pipe(refreshing(url => url.expires < new Date()))
 * ```
 */
export declare const refreshing: <T>(isExpired: (value: T) => boolean, timeout?: number | undefined) => (source: Observable<T>) => Observable<T>;
/**
 * Operator that acts like `takeWhile`, except that **includes** the value
 * matching the predicate rather than rejecting it.
 *
 * Example:
 *
 * ```ts
 * from([1, 2, 3, 4, 5]).pipe(takeUntilFound(num => num === 3))
 * // 1, 2, 3
 * ```
 */
export declare const takeUntilFound: <T>(predicate: (value: T) => boolean) => (source: Observable<T>) => Observable<T>;