import type { AnyIterable, MaybePromise } from "../../types";
/**
 * Applies a given function to each element of the input iterable.
 * Returns the same iterable passed as input.
 *
 * @template T - The type of elements in the input iterable.
 * @param fn - A function that takes an element and its index, applies side effects, and returns nothing.
 * @returns A function that accepts an input iterable and returns an async iterable.
 * @group Lazy helpers
 *
 * @example
 * ```ts
 * using([1, 2, 3])
 *     .forEach((n) => console.log(n)) // Logs 1, 2, and 3
 *     .consume();
 * ```
 */
export declare const forEach: <T>(fn: (element: T, index: number) => MaybePromise<void>) => (input: AnyIterable<T>) => AsyncIterable<Awaited<T>>;
/**
 * Applies a given function to each element of the input iterable.
 * Returns the same iterable passed as input.
 *
 * @template T - The type of elements in the input iterable.
 * @param fn - A function that takes an element and its index, applies side effects, and returns nothing.
 * @returns A function that accepts an input iterable and returns a sync iterable.
 * @group Lazy helpers
 *
 * @example
 * ```ts
 * using([1, 2, 3])
 *     .forEach((n) => console.log(n)) // Logs 1, 2, and 3
 *     .consume();
 * ```
 *
 * @remarks
 * Available as `forEach` when imported from `peter-piper/sync`.
 */
export declare const forEachSync: <T>(fn: (element: T, index: number) => void) => (input: Iterable<T>) => Iterable<T>;