import type { CustomOptions, CustomValidate } from "../custom";
/**
 * Determines if the input is a number.
 *
 * @param input - The value to check.
 * @param validate - Additional validation to run against the input if it is a number. Default is `undefined`.
 * @returns `true` if the input is a number, `false` otherwise.
 *
 * @example
 * ```typescript
 * isNumber(5); // true
 * isNumber(Number.NaN); // false
 * isNumber(Number.POSITIVE_INFINITY); // false
 * ```
 */
export declare function isNumber(input: unknown, validate?: CustomValidate<number>): input is number;
export type NumberOptions = Omit<CustomOptions<number>, "typecheck">;
/**
 * Verifies that the input is a number, and returns it.
 * If the input is not a number, the fallback value is returned.
 *
 * @param input The value to check.
 * @param fallback The value to return if the input is not a number. Default is `null`.
 * @returns The number value of the input, or the fallback if the input is not a number.
 */
export declare function number(input: unknown, fallback: number, options?: NumberOptions): number;
export declare function number(input: unknown, fallback?: number | null | undefined, options?: NumberOptions): number | null;