C++23: Multidimensional Subscript Operator
When you have a class representing multidimensional data, providing access to a specific element in this multidimensional space is often done by providing an operator() with as many parameters as there are dimensions. You had to resort to operator(), because operator[] only supported a single index.
That’s now history, as C++23 introduces the multidimensional subscript operator. Providing such an operator for your class is straightforward:
import std;
template <typename T>
class Matrix
{
public:
Matrix(std::size_t rows, std::size_t cols)
: m_rows{ rows }, m_cols{ cols }
{
m_data.resize(rows * cols);
}
T& operator[](std::size_t x, std::size_t y) { return m_data[x + y * m_cols]; }
private:
std::size_t m_rows;
std::size_t m_cols;
std::vector<T> m_data;
};
The class can be tested as follows:
const std::size_t Rows{4};
const std::size_t Cols{4};
Matrix<int> m{ Rows, Cols };
std::size_t counter{ 0 };
for (std::size_t y{ 0 }; y < Rows; ++y)
{
for (std::size_t x{ 0 }; x < Cols; ++x)
{
m[x, y] = ++counter;
}
}
for (std::size_t y{ 0 }; y < Rows; ++y)
{
for (std::size_t x{ 0 }; x < Cols; ++x)
{
std::print("{} ", m[x, y]);
}
std::println("");
}
