import { Observable, ExtractObservableType } from './observable';
export declare type Deriver<Child, DerivedState> = (state: ExtractObservableType<Child>) => DerivedState;
export interface Derived<Child extends Observable<any>, DerivedState = ExtractObservableType<Child>> extends Observable<DerivedState> {
    child: Child;
}
export declare const derived: <Child extends Observable<any>, DerivedState = ExtractObservableType<Child>>(child: Child, deriver: (state: ExtractObservableType<Child>) => DerivedState) => Derived<Child, DerivedState>;