type Nothing;
type Maybe[T](T | Nothing);

func map[T, U](m: Maybe[T], fn: func(T) -> U) -> Maybe[U] {
    switch m {
        n: Nothing => Nothing,
        t: T => fn(t)
    }
}

func into[T, E](m: Maybe[T], err_fn: fn() -> E) -> Result[T, E] {
    switch m {
        n: Nothing => Err(err_fn),
        t: T => Ok(t),
    }
}

func is_nothing[T](m: Maybe[T]) -> bool {
    switch m {
        n: Nothing => true,
        _ => false
    }
}

func is_some[T](m: Maybe[T]) -> bool {
    m.is_nothing().not()
}