Number of elements in an enum

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
};

But this only works if the items are sequential and start at zero.

From stackoverflow

• Unfortunately, no. There is not.

• 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;
  

  ojblass : can enum types be negative? If so watch out with this one.

  paxdiablo : FIRST=-2 would still calculate correctly, I think: 1 - (-2) = 3.

  Brian Campbell : No need to watch out; subtraction works just fine for negative numbers. Pax has it right.

  ojblass : FIRST = -200, SECOND = -199, THIRD = -198, END = -100. -200 - (-100) = bad news

  ojblass : One case that works does not a proof make.

  ojblass : even sequiental that breaks

  Brian Campbell : I meant sequential as in you only ever set the first value, and let each remaining value increment by default, in sequence. enum blah { FIRST= , SECOND, THIRD, END };

  ojblass : like i am saying thought setting the first to -9 and having 3 elements -9 - (-7) = -2. You need an absolute value or something.

  Brian Campbell : No, you would get FIRST = -9 SECOND = -8 THIRD = -7 END = -6, so you'd have -6 - (-9) = -6 + 9 = 3

  ojblass : ah yes... duh...

  Brian Campbell : No problem; an easy mistake to make.

• 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?

  ojblass : Yes why would you want to do that!

• See this SO question about enums in C++ like in Ada.