How to make a variadic is_same?

Question

How can I make a class template that returns whether any of its variadic types are equal to the first type. I want to be able to do this:

is_same

        

Answer 1

Using the relaxed C++14 constexpr functions, these kinds of things are much easier to code, and probably much faster to compile as well, so you could write:

template 
constexpr bool is_all_same() {
    bool pairs[] = {std::is_same::value...};
    for(bool p: pairs) if(!p) return false;
    return true;
}

template 
constexpr bool is_any_same() {
    bool pairs[] = {std::is_same::value...};
    for(bool p: pairs) if(p) return true;
    return false;
}

This is enabled by the fact that in C++14 constexpr functions can have for loops.