Before inheriting from Matrix, be really, I mean REALLY, sure that using EIGEN_MATRIX_PLUGIN is not what you really want (see previous section). If you just need to add few members to Matrix, this is the way to go.
An example of when you actually need to inherit Matrix, is when you have several layers of heritage such as MyVerySpecificVector1, MyVerySpecificVector2 -> MyVector1 -> Matrix and MyVerySpecificVector3, MyVerySpecificVector4 -> MyVector2 -> Matrix.
In order for your object to work within the Eigen framework, you need to define a few members in your inherited class.
Here is a minimalistic example:
Output:
This is the kind of error you can get if you don't provide those methods
error: no match for ‘operator=’ in ‘v = Eigen::operator*( const Eigen::MatrixBase<Eigen::Matrix<double, -0x000000001, 1, 0, -0x000000001, 1> >::Scalar&, const Eigen::MatrixBase<Eigen::Matrix<double, -0x000000001, 1> >::StorageBaseType&) (((const Eigen::MatrixBase<Eigen::Matrix<double, -0x000000001, 1> >::StorageBaseType&) ((const Eigen::MatrixBase<Eigen::Matrix<double, -0x000000001, 1> >::StorageBaseType*)(& v))))’