How to call my superclass method?

[nuderobmonkey]

I came up with the idea, overloading the opertor[] method from std::vector, within it i need to call std::vector's own operator[] method, but I got stuck with.

Here the code I have so far:

#include <vector>
#include <iostream>

template <typename T>
class Matrix : public std::vector<T>
{
    size_t row_size, col_size;

    struct Row {
        Matrix<T> & mat;
        size_t row;

        Row( Matrix<T> & m, size_t r )
        : mat{m}, row{r}
        {}
        // how could I invoke std::vector's operator[] method?
        T & operator[] ( size_t col ) {
             return std::vector<T>::operator[]( row * mat.col_size + col );
        }
    };

public:
    Matrix( size_t rows, size_t cols)
    : row_size{rows}, col_size{cols}, std::vector<T>(rows*cols)
    {}
    Row operator[] ( size_t row ) { return Row( *this, row ); }
};


int main()
{
    size_t ROWS = 5, COLS = 10;
    Matrix<int> mat( ROWS, COLS );

    for( size_t row = 0; row < ROWS; ++ row)
        for( size_t col = 0; col < COLS; ++ col)
            mat[row][col] = (row+1) * (col+1);

    for( size_t row = 0; row < ROWS; ++ row) {
        for( size_t col = 0; col < COLS; ++ col) {
            std::cout << mat[row][col] << '\t';
        }
        std::cout << '\n';
    }
}

I get this error:

matrix_3.cpp: In instantiation of ‘T& Matrix<T>::Row::operator[](size_t) [with T = int; size_t = long unsigned int]’:
matrix_3.cpp:37:25:   required from here
matrix_3.cpp:18:47: error: cannot call member function ‘std::vector<_Tp, _Alloc>::reference
 std::vector<_Tp, _Alloc>::operator[](std::vector<_Tp, _Alloc>::size_type) [with _Tp = int;
 _Alloc = std::allocator<int>; std::vector<_Tp, _Alloc>::reference = int&; std::vector<_Tp, _Alloc>::size_type
 = long unsigned int]’ without object
   18 |              return std::vector<T>::operator[]( row * mat.col_size + col );
      |                     ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thanks for help.

[Repeater]

The object Matrix inherits from Vector, but your operator[] is part of the Row class. I see that your Row class does contain a Matrix object named mat; did you meant to call it on that Matrix object?

return mat.std::vector<T>::operator[]( row * mat.col_size + col );

[nuderobmonkey]

Thank you Repeater!