s-panferov

interface Result<T, E> {
    map<U>(fn: (a: T) => U): Result<U, E>;
    mapErr<U>(fn: (a: E) => U): Result<T, U>;
    isOk(): boolean;
    isErr(): boolean;
    ok(): Option<T>;
    err(): Option<E>;
    and<U>(res: Result<U,E>): Result<U,E>;
    andThen<U>(op: (T) => Result<U,E>): Result<U,E>;