import type { IEnumerable } from "../../types";
export type SelectFunc = {
    <TSource, TResult>(source: Iterable<TSource>, selector: (x: TSource, index: number) => TResult): IEnumerable<TResult>;
    <TSource, TKey extends keyof TSource>(source: Iterable<TSource>, key: TKey): IEnumerable<TSource[TKey]>;
};
/**
 * Projects each element of a sequence into a new form.
 * @param source A sequence of values to invoke a transform function on.
 * @param selector A key of TSource.
 * @returns
 * An IEnumerable<T> whose elements are the result of getting the value from the key on each element of source.
 */
export declare const select: SelectFunc;