import { Digit, InputNumber } from './type.js';
/**
 * Remove the given character from the left side of the string.
 *
 * @param str the string
 * @param char the character to remove
 * @returns the string with the given character removed from the start
 */
export declare function trimLeft(str: string, char: string): string;
/**
 * Remove the given character from the right side of the string.
 *
 * @param str the string
 * @param char the character to remove
 * @returns the string with the given character removed from the end
 */
export declare function trimRight(str: string, char: string): string;
/**
 * Split the given string into an array of digits.
 *
 * @param str the string
 * @returns an array of digits, or null if the string contains invalid characters
 */
export declare function splitToDigits(str: string): Digit[] | null;
/**
 * Validate the given input number and convert it to a string.
 *
 * @param number the input number
 * @returns a string representation of the number
 * @throws TypeError if the input number is not in a valid type
 */
export declare function validateNumber(number: InputNumber): string;