Why does the C preprocessor consider enum values as equal?

Question

Why does the std::cout line in the following code run even though A and B are different?

#include 

en         


        

Answer 1

Other answers explain why what you're trying doesn't work; for an alternative, I'd probably go with:

#define RGB 1
#define GREY 2
#define CMYK 3
#define MODE RGB

#if MODE == RGB
    //RGB-mode code
#elif MODE == GREY
    //Greyscale code
#elif MODE == CMYK
    //CMYK code
#else
#    error Undefined MODE
#endif

You might want prefixes on the RGB/GREY/CMYK if there's a danger of clashes with "real" source code.