Better Enums

Reflective compile-time C++11 enum library with clean syntax. For example:

ENUM(Channel, int, Red = 1, Green, Blue);

defines a type Channel. You can then do natural things like:

Channel channel = Channel::Green;

channel.to_string();            // Results in the string "Green"
channel.to_integral();          // Results in the int 2

Channel::_from_string("Red");   // Results in Channel::Red
Channel::_from_integral(3);     // Results in Channel::Blue

constexpr auto channel = Channel::_from_integral(3);
                                // Do it at compile time
constexpr auto channel = Channel::_max;
                                // Channel::Blue

for (Channel channel : Channel::_values) {
    // Iterate over all channels
}

...and more. See the project page and examples for a tutorial.

Installation

Simply add enum.h from master to your project.

Features

• Generated at compile time by constexpr functions and the preprocessor.
• Safe conversions between enums and integers and strings. 1-basic.cc
• Iterable collections of constants and names. 2-iterate.cc
• Range information, such as the number of constants defined and the maximum constant. 2-iterate.cc
• Switch case checking. 3-switch.cc
• All operations are constexpr and can be used at compile time in your own constexpr code. 4-constexpr.cc
• Constant values can be set (Red = 1) and aliased (Favorite = Green), just like with built-in enums.
• Generating a large number of enums is about as fast as including a typical standard header like iostream – performance test included.
• Explicit choice of underlying representation type.
• Header-only.
• No dependencies besides the standard library.
• Tested on gcc 4.9 and clang 3.6.

The library is standard C++, but it compiles only with gcc and clang due to lagging C++11 support in msvc. A future runtime fallback version will allow msvc and non-C++11 usage.

Contact

Don't hesitate to contact me about features (or bugs!): antonbachin@yahoo.com

Explanation

The ENUM macro specializes a template based around a regular enum declaration, though it is more similar to enum class in the degree of type safety. The following are spiritually equivalent:

ENUM(Channel, int, Red = 1, Green, Blue);
enum class Channel : int {Red = 1, Green, Blue};

ENUM(Depth, char, Indexed8Bit, HighColor, TrueColor);
enum class Depth : char {Indexed8Bit, HighColor, TrueColor};

See the full documentation.

Development plan

There are several areas that still need improvement.

• Some enum types might have a sensible choice for a default constructor. The library should allow it to be customized.
• All safety checks are currently done by linear scans. This may be a performance problem for enum types with many constants.
• Better diagnostics for empty enums or too many constants.
• Conversions from integers and strings that don't throw exceptions, but indicate failure by some other means.

License

Better Enums is released under the BSD 2-clause license. See LICENSE.

History

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