import type { PipeStep } from './pipe$.js';
import type { AnyAsyncIterable, AnyAwaitableIterable, AnyIterable, AsyncIteratedValue, IteratedValue } from './types/inputs/MinimalIterator.js';
import type { AnySubscribable } from './types/inputs/Subscribable.js';
import type { Observable } from './types/outputs/Observable.js';
import type { SimpleAsyncIterator, SimpleIterator } from './types/outputs/SimpleIterator.js';
export type ScanOrigin<D = unknown> = AnyAwaitableIterable<D> | AnySubscribable<D>;
export type ScanOriginValue<O extends ScanOrigin> = (O extends AnyIterable ? IteratedValue<O> : O extends AnyAsyncIterable ? AsyncIteratedValue<O> : unknown) & (O extends AnySubscribable<infer D> ? D : unknown);
export type ScanCallback<T, S> = (state: S, item: T) => S;
export type ScanResult<O, R> = (O extends AnyIterable ? SimpleIterator<R> : O extends AnyAsyncIterable ? SimpleAsyncIterator<R> : unknown) & (O extends AnySubscribable ? Observable<R> : unknown);
/**
 * Apply reducer-like function to each emitted value, emitting each result.
 *
 * @since 1.0.0
 * @version 2.5.0 Add support for async iterators
 */
export declare function scan$<O extends ScanOrigin, const S>(cb: ScanCallback<ScanOriginValue<O>, S>, init: S): PipeStep<O, ScanResult<O, S>>;