rank() in c++

std::rank in C++ is a template meta-function that retrieves the number of dimensions of an array type. It's a part of the <type_traits> header in the C++ Standard Library.

Here's an example:

#include <iostream>
#include <type_traits>

int main() {
    using ArrayType = int[5][10][15];
    std::cout << "Rank of ArrayType: " << std::rank<ArrayType>::value << std::endl;
    return 0;
}

Explanation:

1. #include <iostream> and #include <type_traits>: These lines include necessary headers for input/output and type traits functionalities respectively.

2. using ArrayType = int[5][10][15];: This line defines a type alias ArrayType for a 3D array of integers with dimensions 5, 10, and 15.

3. std::cout << "Rank of ArrayType: " << std::rank<ArrayType>::value << std::endl;: This line uses std::rank to determine and output the number of dimensions (rank) of the ArrayType. It uses std::rank<ArrayType>::value to retrieve the rank as a compile-time constant and prints it to the console.

4. return 0;: The main function returns 0 to indicate successful completion.

The output of this program will be:

Rank of ArrayType: 3

This indicates that the ArrayType is a 3-dimensional array.