Question

Could one write a function that returns the number of elements in an enum? For example, say I have defined:

enum E {x, y, z};

Then f(E) would return 3.

Answer 1

Nope.

If there were, you wouldn’t see so much code like this:

enum E {
  VALUE_BLAH,
  VALUE_OTHERBLAH,
  ...
  VALUE_FINALBLAH,
  VALUE_COUNT
}

Note that this code is also a hint for a (nasty) solution — if you add a final “guard” element, and don’t explicitly state the values of the enum fields, then the last “COUNT” element will have the value you’re looking for — this happens because enum count is zero-based:

enum  B {
  ONE,   // has value = 0
  TWO,   // has value = 1
  THREE, // has value = 2
  COUNT  // has value = 3 - cardinality of enum without COUNT
}