class - Matrix Multiplication with template parameters in C++ -

i have self-defined matrix class , want overload operator * matrix multiplication:

template< int r, int c>  class matrix{    int *_mat;    int _size; public:    matrix(){ _size = r*c; _mat = new int[_size]{0}; }    ~matrix(){ delete []_mat; }    matrix &operator=(const matrix & m){/*...*/}    //...    template< int d2, int d1 > using matrix_t = int[d2][d1];    template<int r2, int c2>    matrix<r,c2> operator*(const matrix_t<r2,c2> &mat)    {        matrix<r,c2> result;        for(int r = 0; r < r; r++)        {            for(int c = 0; c < c2; c++)            {                for( int i; < c; i++ ){                   /*do multiplication...                     result._mat[r*c2+c] = ...                   */                }            }        }        return result;    }          //... };  

then problem comes matrix<r,c2> result. result becomes outside object of class. cannot access private member using result._mat[r*c2+c].

what solution( without changing access permission) define function of matrix multiplication in class?

you specify operator can externally set values of matrix. note won't able use operator [] - since can use 1 argument (ref c++ [] array operator multiple arguments?)

   int& operator() (int row, int col) {       // todo: check array bounds      return _mat[c*row+col];    } 

usage:

 result(r,c) = ...