import type { AnyIterable, ArrayLikePredicate, AsyncArrayLikePredicate } from "../../types";
/**
 * Yields the first element in an input iterable that satisfies an optional async predicate function.
 * If no predicate is provided, the first element in the iterable is yielded.
 *
 * @group Lazy helpers
 * @template T - The type of elements in the input iterable.
 * @param predicate - An optional async predicate function to test each element of the input iterable.
 * @returns A function that accepts an input iterable and returns a new asynchronous iterable.
 *
 * @example
 * ```ts
 * const input = [1, 2, 3, 4];
 * const isEven = async (x: number) => x % 2 === 0;
 * const firstIterable = first<number>(isEven)(input);
 *
 * (async () => {
 *   for await (const x of firstIterable) {
 *     console.log(x); // Logs 2
 *   }
 * })();
 * ```
 */
export declare const first: <T>(predicate?: AsyncArrayLikePredicate<T> | undefined) => (input: AnyIterable<T>) => AsyncIterable<Awaited<T>>;
/**
 * Yields the first element in an input sync iterable that satisfies an optional predicate function.
 * If no predicate is provided, the first element in the iterable is yielded.
 *
 * @group Lazy helpers
 * @template T - The type of elements in the input sync iterable.
 * @param predicate - An optional predicate function to test each element of the input sync iterable.
 * @returns A function that accepts an input sync iterable and returns a new sync iterable.
 *
 * @example
 * ```ts
 * const input = [1, 2, 3, 4];
 * const isEven = (x: number) => x % 2 === 0;
 * const firstSyncIterable = firstSync<number>(isEven)(input);
 *
 * for (const x of firstSyncIterable) {
 *   console.log(x); // Logs 2
 * }
 * ```
 *
 * @remarks
 * Available as `first` when imported from `peter-piper/sync`.
 */
export declare const firstSync: <T>(predicate?: ArrayLikePredicate<T> | undefined) => (input: Iterable<T>) => Iterable<T>;