import type { Guard } from '../guard/index.js';
import type { Option } from './option.js';
type Filter = {
    <Opt extends Option.Any, Fn extends Guard.Unary>(guard: Fn): (option: Opt) => Option<Guard.UnaryType<Fn>>;
    <Opt extends Option.Any, Fn extends Guard.Unary>(guard: Fn, option: Opt): Option<Guard.UnaryType<Fn>>;
};
/**
 * Calls the provided predicate function on the contained value I if the `Option` is `Some(I)`, and returns `Some(I)` if
 * the function returns `true`; otherwise, returns `None`
 *
 * @tags option, filter, right-biased
 */
export declare const filter: Filter;
export {};