String Literal As Template Argument

Question

These preprocessor and template limitations of c++ are killing me. The goal is to convert string literals into integers.

template<const char* str>
inline int LiteralToInt(){
    return __COUNTER__;
}

using std::cout;

int main(){
    cout << LiteralToInt<"Hello">();
    cout << LiteralToInt<"No">();
    cout << LiteralToInt<"Hello">();
    return 0;
}

The output would be 010 if templates accepted string literals. Is there another way to get this output and convert string literals to integers at compile time?

Answer 1

Yes, C++ 11's constexpr will do this for you:

 constexpr int LiteralToInt(const char * str) {
      return __COUNTER__; // or whatever.
 }

Answer 2

Something like this would work

extern const char HELLO[] = "Hello";

and then

cout << LiteralToInt<HELLO>();

but not the literal itself. This is probably not what you want.

String literals themselves, as you already discovered, cannot be used as template arguments.