import type {
	Predicate,
	ReadOnlyIterable,
	Single,
	Unary,
} from "@lou.codes/types";
/**
 * Filters items in an iterable against a predicate and returns items that
 * evaluated to `true`.
 *
 * @category Generators
 * @example
 * ```typescript
 * const filterEven = filter((number: number) => number % 2 === 0);
 *
 * iterableToArray(filterEven([1, 2, 3, 4])); // [2, 4]
 * iterableToArray(filterEven([1, 3, 5, 7])); // []
 * ```
 * @param predicate Predicate function to evaluate each item.
 * @returns Curried function with `predicate` set in context.
 */
export declare const filter: <Item, Filtered extends Item = never>(
	predicate: Single<Filtered> extends Single<never> ? Unary<Item, boolean>
	:	Predicate<Item, Filtered>,
) => (iterable: ReadOnlyIterable<Item>) => Readonly<IterableIterator<Filtered>>;