import { IObservable, IReader } from "../base.js";
import { DebugOwner } from "../debugName.js";
/**
 * Creates an observable that has the latest changed value of the given observables.
 * Initially (and when not observed), it has the value of the last observable.
 * When observed and any of the observables change, it has the value of the last changed observable.
 * If multiple observables change in the same transaction, the last observable wins.
*/
export declare function latestChangedValue<T extends IObservable<any>[]>(owner: DebugOwner, observables: T): IObservable<ReturnType<T[number]["get"]>>;
/**
 * Works like a derived.
 * However, if the value is not undefined, it is cached and will not be recomputed anymore.
 * In that case, the derived will unsubscribe from its dependencies.
*/
export declare function derivedConstOnceDefined<T>(owner: DebugOwner, fn: (reader: IReader) => T): IObservable<T | undefined>;