Question

I have this bit of code that helps me convert enum to string and vice versa.

So I wrote a macro to make it look better and simpler:

#define SMART_REVERT_CASE(__CODE__, __STRING__)\
     if (__STRING__ == #__CODE__) return __CODE__

And then I call it this way:

enum EXAMPLE { HELLO, GOODBYE, ERROR };
EXAMPLE StringToExample(std::string const& input)
{
  SMART_REVERT_CASE(HELLO, input);
  SMART_REVERT_CASE(GOODBYE, input);
  return ERROR;

}

Unfortunately it does not compile (on VS 2008):

Error   1   error C2666: 'operator ==' : 5 overloads have similar conversions   

Is there a way to give a hint to the compiler as to which operator== to use ?

Answer 1

Just use:

__STRING__.compare( #__CODE__ )

BTW, using double underscores is a bad idea.

The C++11 draft n3290 defines the relevant operator== as:

template<class charT, class traits, class Allocator>
  bool operator==(const basic_string<charT,traits,Allocator>& lhs,
                  const charT* rhs) noexcept;

Requires: rhs points to an array of at least traits::length(rhs) + 1 elements of charT.
Returns: lhs.compare(rhs) == 0.

so compare and == are the same thing here.