class int_vec dim = object (self:'self)
    val mutable _coords = Array.create dim 0

    method dot (x:'self) =
      let rec innerdot sum count =
        if count >= Array.length _coords then sum
        else innerdot (sum + _coords.(count) * x#coords.(count)) (count + 1)
      in
      innerdot 0 0

    method len = sqrt (float (self#dot self))

    method coords = _coords
  end