C custom assignment-CodePudding

I have the following code:

template<size_t rows, size_t cols>
class Matrix{
    std::array<int, rows * cols>  data;
public:
    int  operator()(size_t i, size_t j){
        return data[i * cols   j];
    }
//  ...code...
}

What is the best way to achieve this:

Matrix<1,1> a;
a(0, 0) = 0;

avoiding the lvalue required as left operand of assignment error?

CodePudding user response：

You can change the following line:

int  operator()(size_t i, size_t j){

To:

int & operator()(size_t i, size_t j){

Returning a refernce (L value reference to be precise) to the element in the Matrix will allow you to assign to it.

CodePudding user response：

You need to return the reference of the element from data like this:

// can change
int &operator()(size_t i, size_t j)
{
    return data[i * cols   j];
}

And every STL container includes a const function, for the cases like const Matrix &

// cannot change 
int operator()(size_t i, size_t j) const
{
    return data[i * cols   j];
}