Template Metaprogramming in C++

Its just another programming paradigm

Basically, all the computation is done at compile time itself.
This will increase compilation time, but runtime will be reduced.

In c++ we use templates to perform this.

For e.g. following program computes 2

#include <iostream>
using namespace std;
 
template<int n> struct funStruct
{
    enum { val = 2*funStruct<n-1>::val };
};
 
template<> struct funStruct<0>
{
    enum { val = 1 };
};
 
int main()
{
 // 8 is passed during compilation itself
    cout << funStruct<8>::val << endl;
    return 0;
}

https://en.wikibooks.org/wiki/C%2B%2B_Programming/Templates/Template_Meta-Programming#History_of_TMP

Practical Usecases

1. When computation in your code is not dependent on runtime values
2. Implmentation of std::tuple uses template metaprogramming
3. Boost library functions use template meta programming

Personal Opinion

Still don’t understand why and when this paradigm will be useful, since it can not handle values inputed at runtime

Advanced Video Series

https://www.youtube.com/playlist?list=PLWxziGKTUvQFIsbbFcTZz7jOT4TMGnZBh