I am doing a project using matrices. Eigen is the best C++ matrix library I've found. However, I am required to write my own API for matrix class. So I decide to write a wrapper matrix class based on Eigen.

I wanna to keep all the benefits of Eigen, and therefore I decide to make my wrapper class inherit from Eigen. Here, I found some tutorial,
http://eigen.tuxfamily.org/dox-devel/Cu ... Eigen.html

However, I wanna to prevent my wrapper class calling the Eigen functions directly. So, I wanna to make the inheritance private. Could anybody tell me if the private inheritance is a good thing to do?

I met some problem even for simple multiplication operation. I guess it is because of the expression type. But I can't find the right type. Here is my sample codes

Code: Select all

class MyMatrix : private Eigen::MatrixXd
{
public:
   typedef Eigen::MatrixXd Base;
public:
   MyMatrix() : Eigen::MatrixXd() { }
   MyMatrix(const Eigen::MatrixXd& eMtr) : Eigen::MatrixXd(eMtr) { }

   template<typename OtherDerived>
   MyMatrix& operator= (const Eigen::MatrixBase<OtherDerived>& other)
   {
      this->Base::operator=(other);
      return *this;
   }

   template<typename OtherDerived>
   MyMatrix& operator=(const Eigen::ReturnByValue<OtherDerived>& other)
        {
      this->Base::operator=(other);
      return *this;
        }

   const Eigen::ProductReturnType<Eigen::MatrixXd,Eigen::MatrixXd>::Type
   operator* (const MyMatrix& other) const
   {
      return this->Base::operator*(other);
   }

   template<typename Derived> friend
   const typename Eigen::ProductReturnType<typename     Derived,Eigen::MatrixXd>::Type&
   operator* (const Eigen::MatrixBase<Derived>& m1, const MyMatrix& m2);
};

template<typename Derived>
const typename Eigen::ProductReturnType<typename Derived,Eigen::MatrixXd>::Type
operator* (const Eigen::MatrixBase<Derived>& m1, const MyMatrix& m2)
{
   return m1 * (Eigen::MatrixXd)m2;
};

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int main()
{      
   unsigned N = 100;
   MyMatrix cMtr1 = Eigen::MatrixXd::Random(N,N);
   MyMatrix cMtr2 = Eigen::MatrixXd::Random(N,N);
   MyMatrix cMtr3 = Eigen::MatrixXd::Random(N,N);
   MyMatrix r1, r2;

        r1 = cMtr1 * cMtr2 // works well
   r2 = cMtr1 * cMtr2 * cMtr3; // doesn't work
}


The above does not work for the product of three matrices. Could anybody give me some thought or a solution?

Thank you so much!

there were many mistakes (typename, reference, wrong declaration):

Code: Select all

class MyMatrix : private Eigen::MatrixXd
{
public:
   typedef Eigen::MatrixXd Base;
public:
   MyMatrix() : Eigen::MatrixXd() { }
   MyMatrix(const Eigen::MatrixXd& eMtr) : Eigen::MatrixXd(eMtr) { }

   template<typename OtherDerived>
   MyMatrix& operator= (const Eigen::MatrixBase<OtherDerived>& other)
   {
      this->Base::operator=(other);
      return *this;
   }

   template<typename OtherDerived>
   MyMatrix& operator=(const Eigen::ReturnByValue<OtherDerived>& other)
        {
      this->Base::operator=(other);
      return *this;
        }

   const Eigen::ProductReturnType<Eigen::MatrixXd,Eigen::MatrixXd>::Type
   operator* (const MyMatrix& other) const
   {
      return this->Base::operator*(other);
   }

   template<typename Derived> friend
   const typename ProductReturnType<Derived,Eigen::MatrixXd>::Type
   operator* (const Eigen::MatrixBase<Derived>& m1, const MyMatrix& m2)
   {
     return m1 * static_cast<const Eigen::MatrixXd&>(m2);
   }
};


Thank you very much for your reply. I am new to C++ and doing my first internship. Could you please give me some specific suggestions if I could use private inheritance? I really don't have too much experience with C++. Could you please give me a right direction for wrapping Eigen? I really appreciate your help.

ggael wrote:there were many mistakes (typename, reference, wrong declaration):

Code: Select all

class MyMatrix : private Eigen::MatrixXd
{
public:
   typedef Eigen::MatrixXd Base;
public:
   MyMatrix() : Eigen::MatrixXd() { }
   MyMatrix(const Eigen::MatrixXd& eMtr) : Eigen::MatrixXd(eMtr) { }

   template<typename OtherDerived>
   MyMatrix& operator= (const Eigen::MatrixBase<OtherDerived>& other)
   {
      this->Base::operator=(other);
      return *this;
   }

   template<typename OtherDerived>
   MyMatrix& operator=(const Eigen::ReturnByValue<OtherDerived>& other)
        {
      this->Base::operator=(other);
      return *this;
        }

   const Eigen::ProductReturnType<Eigen::MatrixXd,Eigen::MatrixXd>::Type
   operator* (const MyMatrix& other) const
   {
      return this->Base::operator*(other);
   }

   template<typename Derived> friend
   const typename ProductReturnType<Derived,Eigen::MatrixXd>::Type
   operator* (const Eigen::MatrixBase<Derived>& m1, const MyMatrix& m2)
   {
     return m1 * static_cast<const Eigen::MatrixXd&>(m2);
   }
};


A million thanks with your help! Now, it works well. I've spend one day on this problem. Thanks again for your professional help!

ggael wrote:there were many mistakes (typename, reference, wrong declaration):

Code: Select all

   template<typename Derived> friend
   const typename ProductReturnType<Derived,Eigen::MatrixXd>::Type
   operator* (const Eigen::MatrixBase<Derived>& m1, const MyMatrix& m2)
   {
     return m1 * static_cast<const Eigen::MatrixXd&>(m2);
   }
};