Compact way to write if(..) statement with many equalities

if you want to expand it compile time you can use something like this

template<class T1, class T2>
bool isin(T1&& t1, T2&& t2) {
   return t1 == t2;
}

template<class T1, class T2, class... Ts>
bool isin(T1&& t1 , T2&& t2, T2&&... ts) {
   return t1 == t2 || isin(t1, ts...);
}

std::string my_var = ...; // somewhere in the code
...
bool b = isin(my_var, "fun", "gun", "hun");

I did not test it actually, and the idea comes from Alexandrescu’s ‘Variadic templates are funadic’ talk. So for the details (and proper implementation) watch that.

Edit:
in c++17 they introduced a nice fold expression syntax

template<typename... Args>
bool all(Args... args) { return (... && args); }

bool b = all(true, true, true, false);
 // within all(), the unary left fold expands as
 //  return ((true && true) && true) && false;
 // b is false