import { Kind, Number as Number_, Type } from '..';
type _$stringToDigitMap = {
    '0': 0;
    '1': 1;
    '2': 2;
    '3': 3;
    '4': 4;
    '5': 5;
    '6': 6;
    '7': 7;
    '8': 8;
    '9': 9;
};
/**
 * Given a natural number, return the list of digits.
 *
 * @param {number} x - The natural number to convert to a list of digits.
 *
 * Similar to `NaturalNumber.ToList`, but returns the list of digits as numbers
 * instead of strings.
 *
 * @example
 * ```ts
 * import { NaturalNumber } from "hkt-toolbelt";
 *
 * type Result = NaturalNumber._$digits<42>; // [4, 2]
 * //    ^? [4, 2]
 */
export type _$digits<S extends Number_.Number, O extends number[] = []> = 0 extends 1 ? never : Number_._$toString<S> extends `${infer Head}${infer Tail}` ? _$digits<Tail, Head extends keyof _$stringToDigitMap ? [...O, _$stringToDigitMap[Head]] : never> : O extends [] ? never : O;
/**
 * Given a natural number, return the list of digits.
 *
 * @param {number} x - The natural number to convert to a list of digits.
 *
 * Similar to `NaturalNumber.ToList`, but returns the list of digits as numbers
 * instead of strings.
 *
 * @example
 * ```ts
 * import { NaturalNumber } from "hkt-toolbelt";
 *
 * type Result = $<NaturalNumber.Digits, 42>; // [4, 2]
 * //   ^? [4, 2]
 * ```
 */
export interface Digits extends Kind.Kind {
    f(x: Type._$cast<this[Kind._], Number_.Number>): _$digits<typeof x>;
}
/**
 * Given a natural number, return the list of digits.
 *
 * @param {number} x - The natural number to convert to a list of digits.
 *
 * Similar to `NaturalNumber.ToList`, but returns the list of digits as numbers
 * instead of strings.
 *
 * @example
 * ```ts
 * import { NaturalNumber } from "hkt-toolbelt";
 *
 * const result = NaturalNumber.digits(42)
 * //    ^? [4, 2]
 * ```
 */
export declare const digits: Kind._$reify<Digits>;
export {};