/**
 * Check whether the number is out of range, and give a prompt if it is out of range
 * @param {*number} num
 */
export declare function checkBoundary(num: number): void;
/**
 * Exact multiplication
 *
 * @param {number} x
 * @param {number} y
 * @returns {*}  {number}
 */
export declare function multi(x: number, y: number): number;
/**
 * Exact addition
 *
 * @param {number} x
 * @param {number} y
 * @returns {*}
 */
export declare function plus(x: number, y: number): number;
/**
 * Exact subtraction
 *
 * @param {number} x
 * @param {number} y
 * @returns {*}
 */
export declare function minus(x: number, y: number): number;
/**
 * Exact division
 *
 * @param {number} num1
 * @param {number} num2
 * @returns {*}  {number}
 */
export declare function divide(x: number, y: number): number;
/**
 * rounding
 *
 * @param {number} num
 * @param {number} ratio
 * @returns {*}
 */
export declare function round(num: number, ratio: number): number;