/**
 * Returns a new array formed by applying a given callback function to each
 * element of the array, and then flattening the result by one level. It is
 * identical to a `map` followed by a `flat` of depth 1
 * (`flat(map(data, ...args))`), but slightly more efficient than calling those
 * two methods separately. Equivalent to `Array.prototype.flatMap`.
 *
 * @param data - The items to map and flatten.
 * @param callbackfn - A function to execute for each element in the array. It
 * should return an array containing new elements of the new array, or a single
 * non-array value to be added to the new array.
 * @returns A new array with each element being the result of the callback
 * function and flattened by a depth of 1.
 * @signature
 *    R.flatMap(data, callbackfn)
 * @example
 *    R.flatMap([1, 2, 3], x => [x, x * 10]) // => [1, 10, 2, 20, 3, 30]
 * @dataFirst
 * @lazy
 * @category Array
 */
declare function flatMap<T, U>(data: ReadonlyArray<T>, callbackfn: (input: T, index: number, data: ReadonlyArray<T>) => ReadonlyArray<U> | U): Array<U>;
/**
 * Returns a new array formed by applying a given callback function to each
 * element of the array, and then flattening the result by one level. It is
 * identical to a `map` followed by a `flat` of depth 1
 * (`flat(map(data, ...args))`), but slightly more efficient than calling those
 * two methods separately. Equivalent to `Array.prototype.flatMap`.
 *
 * @param callbackfn - A function to execute for each element in the array. It
 * should return an array containing new elements of the new array, or a single
 * non-array value to be added to the new array.
 * @returns A new array with each element being the result of the callback
 * function and flattened by a depth of 1.
 * @signature
 *    R.flatMap(callbackfn)(data)
 * @example
 *    R.pipe([1, 2, 3], R.flatMap(x => [x, x * 10])) // => [1, 10, 2, 20, 3, 30]
 * @dataLast
 * @lazy
 * @category Array
 */
declare function flatMap<T, U>(callbackfn: (input: T, index: number, data: ReadonlyArray<T>) => ReadonlyArray<U> | U): (data: ReadonlyArray<T>) => Array<U>;

export { flatMap };