/**
 * Converts a value into a Candid-style variant representation of an optional value.
 *
 * @template T The type of the value.
 * @param {T | null | undefined} value - The value to convert into a Candid-style variant.
 * @returns {[] | [T]} A Candid-style variant representation: an empty array for `null` and `undefined` or an array with the value.
 */
export declare const toNullable: <T>(value?: T | null) => [] | [T];
/**
 * Extracts the value from a Candid-style variant representation of an optional value.
 *
 * @template T The type of the value.
 * @param {[] | [T]} value - A Candid-style variant representing an optional value.
 * @returns {T | undefined} The extracted value, or `undefined` if the array is empty.
 */
export declare const fromNullable: <T>(value: [] | [T]) => T | undefined;
/**
 * Extracts the value from a Candid-style variant representation of an optional value,
 * ensuring the value is defined. Throws an error if the array is empty or the value is nullish.
 *
 * @template T The type of the value.
 * @param {[] | [T]} value - A Candid-style variant representing an optional value.
 * @returns {T} The extracted value.
 * @throws {Error} If the array is empty or the value is nullish.
 */
export declare const fromDefinedNullable: <T>(value: [] | [T]) => T;
/**
 * Extracts the value from a nullish Candid-style variant representation.
 *
 * @template T The type of the value.
 * @param {([] | [T]) | undefined} value - A Candid-style variant or `undefined`.
 * @returns {T | undefined} The extracted value, or `undefined` if the input is nullish or the array is empty.
 */
export declare const fromNullishNullable: <T>(value: ([] | [T]) | undefined) => T | undefined;