T2688.hs:8:22:
    Couldn't match expected type ‘v’ with actual type ‘s’
      ‘s’ is a rigid type variable bound by
          the class declaration for ‘VectorSpace’ at T2688.hs:5:21
      ‘v’ is a rigid type variable bound by
          the class declaration for ‘VectorSpace’ at T2688.hs:5:19
    In the second argument of ‘(/)’, namely ‘s’
    In the second argument of ‘(*^)’, namely ‘(1 / s)’
    Relevant bindings include
      s :: s (bound at T2688.hs:8:10)
      v :: v (bound at T2688.hs:8:5)
      (^/) :: v -> s -> v (bound at T2688.hs:8:5)