Function casting

packages/eigen-eigen-323c052e1731/test/basicstuff.cpp:182–189

#ifdef EIGEN_TEST_PART_2
void casting()
{
  Matrix4f m = Matrix4f::Random(), m2;
  Matrix4d n = m.cast<double>();
  VERIFY(m.isApprox(n.cast<float>()));
  m2 = m.cast<float>(); // check the specialization when NewType == Type
  VERIFY(m.isApprox(m2));
}
#endif

template <typename Scalar>