/**
 * A successful value
 */
export declare type Ok<R> = {
    _tag: 'ok';
    value: R;
};
/**
 * A failed value
 */
export declare type Err<L> = {
    _tag: 'error';
    error: L;
};
/**
 * A safe result type: imagine a language with no exceptions — the way to handle
 * errors would be to use something like a tagged union type.
 *
 * Why would we want that? I want to explicitly handle exceptions in this library
 * and having this construct really helps. It's also pretty easy to implement.
 */
export declare type Result<L, R> = Err<L> | Ok<R>;
export declare function ok<O>(value: O): Ok<O>;
export declare function err<E>(error: E): Err<E>;
/**
 * Checks whether a value is an `Ok`.
 * Handy with TypeScript guards
 */
export declare function isOk<R>(result: Result<any, R>): result is Ok<R>;
/**
 * Checks whether a value is an `Err`.
 * Handy with TypeScript guards
 */
export declare function isErr<L>(either: Result<L, any>): either is Err<L>;
/**
 * Convert a `Promise<T>` into a `Promise<Result<Error, T>>`,
 * therefore catching the errors and being able to handle them explicitly
 */
export declare function safeAsync<O>(promise: Promise<O>): Promise<Result<Error, O>>;