How does C 23 Enhance Operator Overloading for Multi-Argument Arrays?

Operator Overloading for Multi-Argument Arrays in C

In C , it is possible to define an array operator that takes multiple arguments to access the elements of an array efficiently. However, it was previously not possible to overload the default array operator ([]) to accept more than one argument. This limitation restricted the creation of custom array-like classes that required multiple indices to access their elements.

Pre-C 23 Workaround

To address this issue, a workaround could be employed prior to C 23. Instead of overloading the [], programmers would overload the () operator and specify the additional parameters as arguments to the function call. Here's an example:

class Matrix {
    private:
        std::vector<int> m_cells;
        int m_res;
        int m_resSqr;
    public:
        int& operator()(const int i, const int j) { 
            return m_cells[j * m_res + i];
        }
};

This approach allowed programmers to achieve similar functionality without violating the C language rules.

C 23 Enhancement

With the introduction of C 23, the language standard has been updated to allow for multiple subscript arguments to be passed to the [] operator. This change provides a more natural and concise syntax for working with arrays that require multiple indices for indexing.

Example

The following code demonstrates the syntax for operator[] overloading with multiple arguments in C 23:

class Matrix {
    private:
        std::vector<int> m_cells;
        int m_res;
        int m_resSqr;
    public:
        const T& operator[](const int i, const int j, const int k) const {
            return m_cells[k * m_resSqr + j * m_res + i];
        }
        T& operator[](const int i, const int j, const int k) {
            return m_cells[k * m_resSqr + j * m_res + i];       
        }
};

Using this syntax, you can access elements of the Matrix class using multiple indices as follows:

Matrix matrix;
int value = matrix[2, 5, 7];

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