Is it possible to determine the number of elements of a c++ enum class?

Question

Is it possible to determine the cardinality of a c++ enum class:

enum class Example { A, B, C, D, E };

I tried to use si

Answer 1

constexpr auto TEST_START_LINE = __LINE__;
enum class TEST { // Subtract extra lines from TEST_SIZE if an entry takes more than one 
    ONE = 7
  , TWO = 6
  , THREE = 9
};
constexpr auto TEST_SIZE = __LINE__ - TEST_START_LINE - 3;

This is derived from UglyCoder's answer but improves it in three ways.

• There are no extra elements in the type_safe enum (BEGIN and SIZE) (Cameron's answer also has this problem.)
  • The compiler will not complain about them being missing from a switch statement (a significant problem)
  • They cannot be passed inadvertently to functions expecting your enum. (not a common problem)
• It does not require casting for use. (Cameron's answer has this problem too.)
• The subtraction does not mess with the size of the enum class type.

It retains UglyCoder's advantage over Cameron's answer that enumerators can be assigned arbitrary values.

A problem (shared with UglyCoder but not with Cameron) is that it makes newlines and comments significant ... which is unexpected. So someone could add an entry with whitespace or a comment without adjusting TEST_SIZE's calculation.