I'm trying to inherit from SparseMatrix where the non-type template parameters determine the size of the matrix. These parameters are not the sizes themselves but instead are used to compute the size:

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typedef Eigen::SparseMatrix<double, Eigen::RowMajor> sparse_matrix;

template<enumT T1, size_t N1, enumT T2, size_t N2>
class myMatrix : public sparse_matrix {
   
public:
   
   static const enumT t1 = T1;
   static const size_t n1 = N1;
   static const enumT t2 = T2;
   static const size_t n2 = N2;
   
   myMatrix (const inputObj& input)
   :
      sparse_matrix ()
   {      
      size_t nCols (// compute num cols from templates and input);
      
      size_t nRows (// compute num rows from templates and input);
      
      this->resize (nRows, nCols);      
   }

template <typename derived>
   myMatrix& operator= (const Eigen::SparseMatrixBase<derived>& other) {
      this->sparse_matrix::operator= (other);
      return *this;
   }
}
;

I'm trying to get this class to multiply correctly but can't figure it out. I tried the following:

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template <typename derived>
myMatrix<derived::t1, derived::n1, T2, N2> operator* (const Eigen::SparseMatrixBase<derived>& rhs) {
   
   myMatrix<derived::t1, derived::n1, T2, N2> x  = this->sparse_matrix::operator * (rhs);
   return x;
}


And then tried calling:

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myMatrix<enumT::T0, 0, enumT::T0, 1> x;
myMatrix<enumT::T0, 1, enumT::T1, 1> y;
myMatrix<enumT:T0, 0, enumT::T1, 1> prod = x * y;


Anybody know how(if) this can be done?

adding:

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using sparse_matrix::operator=;

in the public section might help.

btw, what's the purpose of having sizes determined from compile time parameters? for small dense matrices it does make sense, but not for sparse matrices.