Check if a type is passed in variadic template parameter pack

Question

I\'ve heard somewhere, that using new C++1z syntax, it is really easy to check if a type is passed in variadic template parameter pack - apparently you can do this with code

Answer 1

If you are bound to C++11 you cannot use std::disjunction nor fold-expressions. However, it is rather straightforward to roll your own any_is_same:

template 
struct any_is_same {
    static const bool value = std::is_same::value || 
                              any_is_same::value; 
};

template 
struct any_is_same : std::is_same {};


int main(){
    std::cout << any_is_same::value << "\n";
    std::cout << any_is_same::value << "\n";
}

Live Demo