type Result*[T, E] {
    Ok(value: T)
    Err(error: E)
}

fn is-ok*[T, E](result: &Result[T, E]) bool =
    match result {
        Result.Ok(_) -> true
        Result.Err(_) -> false
    }

fn is-err*[T, E](result: &Result[T, E]) bool =
    !result.is-ok()

fn map*[A, B, E](result: Result[A, E], f: fn(A) B) Result[B, E] =
    match result {
        Result.Ok(v) -> Result.Ok(f(v))
        Result.Err(e) -> Result.Err(e)
    }