import { Type, Kind } from '..';
type _$simpleJoin<T extends (string | number)[], O extends string = ''> = T extends [
    infer Head extends string | number,
    ...infer Tail extends (string | number)[]
] ? _$simpleJoin<Tail, `${O}${Head}`> : O;
/**
 * Given a list of digits, return a natural number.
 *
 * @param {Digit.Digit[]} T - The list of digits.
 *
 * @example
 * ```ts
 * import { NaturalNumber } from "hkt-toolbelt";
 *
 * type T0 = NaturalNumber._$undigits<[1, 2, 3]>; // 123
 * type T1 = NaturalNumber._$undigits<[4, 5, 6]>; // 456
 * ```
 */
export type _$undigits<T extends (string | number)[]> = _$simpleJoin<T> extends `${infer N extends number}` ? N : never;
/**
 * Given a list of digits, return a natural number.
 *
 * @param {Digit.Digit[]} T - The list of digits.
 *
 * @example
 * ```ts
 * import { NaturalNumber } from "hkt-toolbelt";
 *
 * type T0 = $<NaturalNumber.Undigits, [1, 2, 3]>; // 123
 * type T1 = $<NaturalNumber.Undigits, [4, 5, 6]>; // 456
 * ```
 */
export interface Undigits extends Kind.Kind {
    f(x: Type._$cast<this[Kind._], (string | number)[]>): _$undigits<typeof x>;
}
/**
 * Given a list of digits, return a natural number.
 *
 * @param {Digit.Digit[]} T - The list of digits.
 *
 * @example
 * ```ts
 * import { NaturalNumber } from "hkt-toolbelt";
 *
 * const T0 = NaturalNumber.undigits([1, 2, 3]); // 123
 * const T1 = NaturalNumber.undigits([4, 5, 6]); // 456
 * ```
 */
export declare const undigits: Kind._$reify<Undigits>;
export {};