Check for multiple values when using comparison operators

Question

I\'ve always been under the impression that for any comparison statement, i.e. X == Y or X != Y is the format, and you chain statements together with <

Answer 1

#include 
#include 
#include 
#include 
#include 
 
template
bool is_one_of(const Type& needle, const Next& next)
{return needle==next;}
template
bool is_one_of(const Type& needle, const Next& next, Rest... haystack)
{return needle==next || is_one_of(needle, haystack...);}
 
int main() {
    std::string X, Y;
    if (is_one_of(X, Y, "HI"))
        std::cout << "it is!";
    else
        std::cout << "it isn't!";
    return 0;
}

proof of compilation. Xeo also observes that std::any_of, std::all_of and std::none_of may have been useful, depending on your actual needs and desires.