Different enums, same value

Question

Is it possible to make two different enums with a same value? For example,

enum direction{
    LEFT,
    RIGHT,
    UP,
    DOWN,
    NONE
}
enum color{
   RED,
   GREEN,
   BLUE,
   NONE
}

The compiler would say that there are two declarations of 'NONE'. Is there a way around this?

Answer 1

There's a couple ways around this. One way is to use namespaces to wrap enums and prevent the values from polluting the global namespace:

namespace direction {
    enum direction {
        LEFT,
        RIGHT,
        UP,
        DOWN,
        NONE
    };
}
namespace color {
    enum color {
       RED,
       GREEN,
       BLUE,
       NONE
    };
}

You can also use the new C++11 way (if your compiler supports it) and use "strongly-typed enums"

enum class direction {
    LEFT,
    RIGHT,
    UP,
    DOWN,
    NONE
};
enum class color {
   RED,
   GREEN,
   BLUE,
   NONE
};

Both can be used by the syntax direction::NONE or color::NONE but there is one major difference. In the first case the enums will still implicitly cast to ints. This means you can write

int foo = direction::NONE;

and everything is fine.

In the second case, this would be a compiler error since foo is not the same type as direction. You can get around this by doing

direction foo = direction::NONE;

which may or may not work for you. If you need to cast it to an int, you are welcome to use static_cast<int>(foo) to get an integer type.