/**
 * represents a simple "present or absent" type.
 *
 * This is very similar to existing implementations, e.g. in fp-ts
 * and differs mostly in that the types are a bit more relaxed.
 *
 * @module
 */
export type Option<T> = Readonly<{
    __tag: "some";
    value: T;
} | {
    __tag: "none";
}>;
export declare const some: <T>(value: T) => Option<T>;
export declare const none: Option<never>;
export declare const fromNullable: <T>(value: T | undefined | null) => Option<T>;
export declare const map: <T, U>(fn: (value: T) => U) => (option: Option<T>) => Option<U>;
export declare const flatMap: <T, U>(fn: (value: T) => Option<U>) => (option: Option<T>) => Option<U>;
export declare const match: <T, R>(onNone: () => R, onSome: (value: T) => R) => (option: Option<T>) => R;
export declare const getOrElse: <T, F>(fn: () => F) => (option: Option<T>) => T | F;
export declare const toUndefined: <T>(option: Option<T>) => T | undefined;
export declare const alt: <T>(second: Option<T>) => (first: Option<T>) => Option<T>;
/**
 * attempt to evaluate a function, returns none if evaluation throws
 */
export declare const attempt: <T>(fn: () => T) => Option<T>;