/**
 * Utilities for iterable objects. Use this module by importing from from
 * `@sirpepe/shed/iterable`.
 */
/**
 * Groups the elements of an iterable in an array by a key and organizes the
 * arrays in a map. The map's keys are generated by a selector which can either
 * be a function or a key for any property on the elements. The selector
 * function (if provided) is invoked with one argument (the current value).
 *
 * Examples:
 *
 * ```typescript
 * const input = [
 *   { x: 0, y: "a" },
 *   { x: 1, y: "b" },
 *   { x: 2, y: "a" },
 *   { x: 3, y: "c" },
 *   { x: 4, y: "b" },
 * ];
 *
 * const fromProperty = groupBy(input, "y");
 * // returns: Map {
 * //   "a" => [{ x: 0, y: "a" }, { x: 2, y: "a" }],
 * //   "b" => [{ x: 1, y: "b" }, { x: 4, y: "b" }],
 * //   "c" => [{ x: 3, y: "c" }],
 * // }
 *
 * const fromFunction = groupBy(input, (value) => value.y.charCodeAt(0) % 2)
 * // returns: Map {
 * //   1 => [{ x: 0, y: "a" }, { x: 2, y: "a" }, { x: 3, y: "c" }],
 * //   0 => [{ x: 1, y: "b" }, { x: 4, y: "b" }, { x: 5, y: "b" }],
 * // }
 * ```
 */
export declare function groupBy<T, Key extends keyof T>(input: Iterable<T>, selector: Key): Map<T[Key], T[]>;
export declare function groupBy<T, Key>(input: Iterable<T>, selector: (element: T, index: number) => Key): Map<Key, T[]>;
/**
 * Organizes the elements of an iterable in a map. The map's keys are generated
 * by a selector which can either be a function or a key for any property on the
 * elements. The selector function (if provided) is invoked with one argument
 * (the current value). If the selector function produces the same key twice, it
 * will throw an error.
 *
 * Examples:
 *
 * ```typescript
 * ```
 */
export declare function mapBy<T, Key extends keyof T>(values: Iterable<T>, selector: Key): Map<T[Key], T>;
export declare function mapBy<T, Key>(values: Iterable<T>, selector: (element: T, index: number) => Key): Map<Key, T>;
/**
 * Splits an iterable into two groups. The first group contains elements
 * the predicate function returns truthy for, the second group contains elements
 * the predicate returns falsy for. The predicate is invoked with one argument
 * (the current value).
 *
 * Examples:
 *
 * ```typescript
 * ```
 */
export declare function partition<T>(input: Iterable<T>, predicate: (element: T) => boolean): [T[], T[]];
export declare function partition<T, U>(input: Iterable<T | U>, predicate: (element: T | U) => element is T): [T[], U[]];