{1.f, 2.f, 3.f} * 2.f = {2.f, 4.f, 6.f}
{1.f, 0.f} + {0.f, 1.f} = {1.f, 1.f}

template<class T, size_t N>
class Vec : public std::array<T, N>
{
  friend Vec<T, N>& operator*=(Vec<T, N>& a, const Vec<T, N>& b)
  {
    std::transform(a.begin(), a.end(), b.begin(), a.begin(), std::multiplies<>());
    return a;
  }

  template<class S>
  friend Vec<T, N>& operator*=(Vec<T, N>& a, const S& b)
  {
    std::transform(a.begin(), a.end(), a.begin(), [&] (T x) { return x*b; });
    return a;
  }

  template<class S>
  friend Vec<T, N> operator*(Vec<T, N> a, const S& b)
  {
    return a *= b;
  }
};
using Vec2 = Vec<float, 2>;

Vec2 a{1.f, 1.f};
auto b = a * 0.5f; // b = {.5f, .5f} <- as expected
auto c = 0.5f * a; // c = {.5f, 0.f} <- what happened here?