Better Enums  

Reflective compile-time enum library with clean syntax, in a single header file, and without dependencies.

Note: consider magic_enum (if using GCC, requires at least GCC 9.0).

In C++11, everything can be used at compile time. You can convert your enums, loop over them, find their max, statically enforce conventions, and pass along the results as template arguments or to constexpr functions. All the reflection is available for your metaprogramming needs.

The interface is the same for C++98 — you just have to use most of it at run time only. This library does provide scoped and sized enums, something not built into C++98.

See the project page for full documentation.

Installation

Simply add enum.h to your project.

Additional features

• Uses only standard C++, though, for C++98, variadic macro support is required (major compilers have it).
• Supported and tested on clang, gcc, and msvc.
• Fast compilation. You have to declare a few dozen enums to slow down your compiler as much as only including iostream does.
• Use any initializers and sparse ranges, just like with a built-in enum.
• Control over size and alignment — you choose the representation type.
• Stream operators.
• Does not use the heap and can be compiled with exceptions disabled, for use in minimal freestanding environments.

Limitations

1. The biggest limitation is that the BETTER_ENUM macro can't be used inside a class. This seems difficult to remove. There is a workaround with typedef (or C++11 using):

   BETTER_ENUM(SomePrefix_Color, uint8_t, Red, Green, Blue)
   
   struct triplet {
       typedef SomePrefix_Color    Color;
       Color                       r, g, b;
   };
   
   triplet::Color  color;

   You can, however, use BETTER_ENUM inside a namespace.

2. The macro has a soft limit of 64 declared constants. You can extend it by following these instructions. Ultimately, the number of constants is limited by your compiler's maximum macro argument count.

3. In some cases, it is necessary to prefix constants such as Channel::Red with a + to explicitly promote them to type Channel. For example, if you are doing a comparison:

   channel == +Channel::Red

4. On msvc, you may need to enable warning C4062 to get switch case exhaustiveness checking.

Contact and development

Don't hesitate to contact me about features or bugs: antonbachin@yahoo.com, or open an issue on GitHub.

If you'd like to help develop Better Enums, see CONTRIBUTING. One area that could use fresh ideas is finding a compile-time data structure that both compiles quickly and allows lookup in sub-linear time.

History

The original version of the library was developed by the author in the winter of 2012-2013 at Hudson River Trading, as a replacement for an older generator called BETTER_ENUM.