import type { AnyIterable, AsyncReducer, Reducer } from "../../types";
/**
 * Reduces an input iterable to a single value using an asynchronous reducer function.
 *
 * @group Greedy helpers
 * @template T - The type of elements in the input iterable.
 * @template U - The type of the output value. Defaults to `T`.
 * @param reducer - An asynchronous reducer function that takes the accumulator, a value, and its index.
 * @param initialValue - Optional. The initial value of the accumulator. If not provided, the first value of the iterable is used.
 * @returns A function that accepts an input iterable and returns a Promise that resolves to the reduced value.
 *
 * @example
 * ```ts
 * const input = [1, 2, 3];
 * const add = async (acc: number, value: number) => acc + value;
 * const sum = reduce(add)(input);
 *
 * (async () => {
 *   console.log(await sum); // Logs 6
 * })();
 * ```
 */
export declare function reduce<T, U = T>(reducer: AsyncReducer<T, U>, initialValue?: U): (input: AnyIterable<T>) => Promise<U>;
/**
 * Reduces an input sync iterable to a single value using a reducer function.
 *
 * @group Greedy helpers
 * @template T - The type of elements in the input sync iterable.
 * @template U - The type of the output value. Defaults to `T`.
 * @param reducer - A reducer function that takes the accumulator, a value, and its index.
 * @param initialValue - Optional. The initial value of the accumulator. If not provided, the first value of the iterable is used.
 * @returns A function that accepts an input sync iterable and returns the reduced value.
 *
 * @example
 * ```ts
 * const input = [1, 2, 3];
 * const add = (acc: number, value: number) => acc + value;
 * const sumSync = reduceSync(add)(input);
 *
 * console.log(sumSync); // Logs 6
 * ```
 *
 * @remarks
 * Available as `reduce` when imported from `peter-piper/sync`.
 */
export declare function reduceSync<T, U = T>(reducer: Reducer<T, U>, initialValue?: U): (input: Iterable<T>) => U;