import { E as ExactRecord } from './ExactRecord-Do0Gswzd.cjs';
import { N as NonEmptyArray } from './NonEmptyArray-C9Od1wmF.cjs';
import './IfBoundedRecord-WIX9x_oz.cjs';
import 'type-fest';

/**
 * Groups the elements of a given iterable according to the string values
 * returned by a provided callback function. The returned object has separate
 * properties for each group, containing arrays with the elements in the group.
 * Unlike the built in `Object.groupBy` this function also allows the callback to
 * return `undefined` in order to exclude the item from being added to any
 * group.
 *
 * @param data - The items to group.
 * @param callbackfn - A function to execute for each element in the iterable.
 * It should return a value indicating the group of the current element, or
 * `undefined` when the item should be excluded from any group.
 * @returns An object with properties for all groups, each assigned to an array
 * containing the elements of the associated group.
 * @signature
 *    R.groupBy(data, callbackfn)
 * @example
 *    R.groupBy([{a: 'cat'}, {a: 'dog'}] as const, R.prop('a')) // => {cat: [{a: 'cat'}], dog: [{a: 'dog'}]}
 *    R.groupBy([0, 1], x => x % 2 === 0 ? 'even' : undefined) // => {even: [0]}
 * @dataFirst
 * @category Array
 */
declare function groupBy<T, Key extends PropertyKey = PropertyKey>(data: ReadonlyArray<T>, callbackfn: (value: T, index: number, data: ReadonlyArray<T>) => Key | undefined): ExactRecord<Key, NonEmptyArray<T>>;
/**
 * Groups the elements of a given iterable according to the string values
 * returned by a provided callback function. The returned object has separate
 * properties for each group, containing arrays with the elements in the group.
 * Unlike the built in `Object.groupBy` this function also allows the callback to
 * return `undefined` in order to exclude the item from being added to any
 * group.
 *
 * @param callbackfn - A function to execute for each element in the iterable.
 * It should return a value indicating the group of the current element, or
 * `undefined` when the item should be excluded from any group.
 * @returns An object with properties for all groups, each assigned to an array
 * containing the elements of the associated group.
 * @signature
 *    R.groupBy(callbackfn)(data);
 * @example
 *    R.pipe(
 *      [{a: 'cat'}, {a: 'dog'}] as const,
 *      R.groupBy(R.prop('a')),
 *    ); // => {cat: [{a: 'cat'}], dog: [{a: 'dog'}]}
 *    R.pipe(
 *      [0, 1],
 *      R.groupBy(x => x % 2 === 0 ? 'even' : undefined),
 *    ); // => {even: [0]}
 * @dataLast
 * @category Array
 */
declare function groupBy<T, Key extends PropertyKey = PropertyKey>(callbackfn: (value: T, index: number, data: ReadonlyArray<T>) => Key | undefined): (items: ReadonlyArray<T>) => ExactRecord<Key, NonEmptyArray<T>>;

export { groupBy };