Number of elements in an enum

Question

In C, is there a nice way to track the number of elements in an enum? I\'ve seen

enum blah {
    FIRST,
    SECOND,
    THIRD,
    LAST
};

Answer 1

I know this is a very old question, but as the accepted answer is wrong, I feel compelled to post my own. I'll reuse the accepted answer's example, slightly modified. (Making the assumption that enums are sequential.)

// Incorrect code, do not use!
enum blah {
  FIRST   =  0,
  SECOND, // 1
  THIRD,  // 2
  END     // 3
};
const int blah_count = END - FIRST;
// And this above would be 3 - 0 = 3, although there actually are 4 items.

Any developer knows the reason: count = last - first + 1. And this works with any combination of signs (both ends negative, both positive, or only first end negative). You can try.

// Now, the correct version.
enum blah {
  FIRST   =  0,
  SECOND, // 1
  THIRD,  // 2
  END     // 3
};
const int blah_count = END - FIRST + 1; // 4

Edit: reading the text again, I got a doubt. Is that END meant not to be part of the offered items? That looks weird to me, but well, I guess it could make sense...

Answer 2

Unfortunately, no. There is not.

Answer 3

Well, since enums can't change at run-time, the best thing you can do is:

enum blah {
    FIRST = 7,
    SECOND = 15,
    THIRD = 9,
    LAST = 12
};
#define blahcount 4 /* counted manually, keep these in sync */

But I find it difficult to envisage a situation where that information would come in handy. What exactly are you trying to do?

Answer 4

I don't believe there is. But what would you do with such a number if they are not sequential, and you don't already have a list of them somewhere? And if they are sequential but start at a different number, you could always do:

enum blah {
    FIRST = 128,
    SECOND,
    THIRD,
    END
};
const int blah_count = END - FIRST;

Answer 5

If you don't assign your enums you can do somethings like this:

enum MyType {
  Type1,
  Type2,
  Type3,
  NumberOfTypes
}

NumberOfTypes will evaluate to 3 which is the number of real types.

Answer 6

int enaumVals[] =
{
FIRST,
SECOND,
THIRD,
LAST
};

#define NUM_ENUMS sizeof(enaumVals) / sizeof ( int );