Interesting template usage

[Ceset]

Hi everyone

I was reading articles and questions people asked at internet about static_assert, so that i can learn about it.

I came across this question, that is asked by PorkyBrain
http://stackoverflow.com/questions/17577749/why-is-comparing-two-parameters-of-a-constexpr-function-not-a-constant-condition

Q1 : Something took my attention there. Guy uses template specifically for int, and not for a generic type. I couldnt find an example usage like that on internet.

Q2 : template<int i,int Size> in function parameters guy did not passed 'i', but used it inside function definition.

Q3 : If that function is working how can i use that function? Like
BitPositionToMask(); ??? where do i add 'i' integer as an argument.

My questions could be silly, and sorry if it is. I just got confused by this.

Thanks in advance

[keskiverto]

Template metaprogramming is actually older than the C++ standard.

Example: http://cpptruths.blogspot.fi/2011/07/want-speed-use-constexpr-meta.html

These are legal:

template <int N>
void foo() {
  std::cout << N;
}

template <typename T>
void bar( int x ) {
  std::cout << static_cast<T>( x );;
}

// use
foo<42>();
bar<double>( 7 );

(Earlier MSVC did not support the syntax and one was forced to add dummy parameters to help the template type deduction.)

[Ceset]

Wow, pretty interesting. Thank you for the answer.

Going to try it out today.

EDIT : Tried it out and it is awesome.