import type { Callback } from '../../types/Callback.js';
/**
 * Calls a defined callback function on each element of an array, and
 * returns the total (using `+`) of all the callback return values, or
 * zero if the array is empty.
 *
 * @param callback - A function that accepts up to three arguments. The
 *  sum method calls the callback function one time for each
 *  element in the array.
 */
export declare const sum: <T>(arr: readonly T[], callback?: Callback<T, number>) => number;