error C2676 when compiling

I'm trying to write code in C++ (using template) to add between 2 matrices. I have the following code in .h file. ``` #ifndef __MATRIX_H__ #define __MATRIX_H__ //*************************** // matrix //*************************** template <class T, int rows, int cols> class matrix { public: T mat[rows][cols]; matrix(); matrix(T _mat[rows][cols]); matrix operator+(const matrix& b); }; template <class T, int rows, int cols> matrix <T,rows,cols> :: matrix (T _mat[rows][cols]){ for (int i=0; i<rows; i++){ for (int j=0; j<cols; j++){ mat[i][j] = _mat[i][j]; } } } template <class T, int rows, int cols> matrix <T,rows,cols> :: matrix (){ for (int i=0; i<rows; i++){ for (int j=0; j<cols; j++){ mat[i][j] = 0; } } } template <class T, int rows, int cols> matrix <T,rows,cols> matrix <T,rows,cols>::operator+(const matrix<T, rows, cols>& b){ matrix<T, rows, cols> tmp; for (int i=0; i<rows; i++){ for (int j=0; j<cols; j++){ tmp[i][j] = this->mat[i][j] + b.mat[i][j]; } } return tmp; } #endif ``` my .cpp : ``` #include "tar5_matrix.h" int main(){ int mat1[2][2] = {1,2,3,4}; int mat2[2][2] = {5,6,7,8}; matrix<int, 2, 2> C; matrix<int, 2, 2> A = mat1; matrix<int, 2, 2> B = mat2; C = A+B; return 0; } ``` When compiling, I get the following error: 1>c:\users\karin\desktop\lior\study\cpp\cpp_project\cpp_project\tar5_matrix.h(36): error C2676: binary '[' : 'matrix' does not define this operator or a conversion to a type acceptable to the predefined operator Please advise