* what the problem is that needs solving,
* how the lib solves it and how that's preferable over dealing with the problem another way,
* how it compares to other libs that solve the same problem.
Therefore my interest in using this for my own projects right now is unfortunately close to zero.
- The problem is basically twofold. Part (a) is that there are no facilities for dealing with enums in C++. "Dealing with" could be anything, such as: bitwise-combining enums as flags, converting enums to/from strings, verifying that a given value is valid for an enum, decomposing flags into their constituent values, and anything else people might typically want to do with enums. Part (b) is that people end up manually writing enum-specific functions for these over and over again, and that often results in brittle and non-reusable code that quickly gets out of sync with the actual enum as it evolves over time (e.g., handwritten parsing code might stop working when a new member is added). This library aims to address most if not all of these problems.
- There are 3 main "tricks" I've used (and a ton of boilerplate on top of that): (a) I use the auto-return-type-with-hidden-friends trick to "tag" the enum with metadata for later retrieval, (b) I overload the comma operator to be able to utilize the same text for both the enum definition as well as for storing relevant metadata, and (c) I use constexpr string parsing to extract the enum names from the definition passed to the macro. Part (a) is confusing and better explained in the link I put in the credits. Part (b) is somewhat tricky but hopefully not too bad. Part (c) seems obvious in hindsight now that I mention it, but I haven't seen it used elsewhere in this manner. (Edit: While digging further just now, I found someone has indeed tried a similar approach with constexpr string parsing in [1], though it appears less comprehensive.)
- No other libraries that I'm aware of support all the features of this one. Typical restrictions include: limiting the ranges of the underlying values, limiting the number of enumerators to some amount, not supporting enum members with duplicate values, not supporting 'enum class', etc.
Hope this helps! If I can clarify anything else please let me know.
[1] https://github.com/therocode/meta_enum/blob/master/include/m...
No string -> enum would probably be a non-starter for me though
Update: And I'm glad to see interest! I just updated the repo to add a parse_enum function for converting strings to enums as well.
[1] https://github.com/Neargye/magic_enum/blob/master/doc/limita...
Nowadays I just keep myself to writing .NET, touching C++/WinRT as little as possible.
It needs to be a special kind of developer to love to write by hand, without any tooling support, what C++/CX reflection offered out of the box.
But I believe for this type of problem it can be clarifying to begin by identifying a handful of things you should be able to do, and then baking those in. This helps because now competing proposals for how to do compile time reflection have an example application. How does your proposal make the agreed enum-to-string syntax work ? It must do that or it's not a proposal to solve the problem we agreed we have. And meanwhile the ordinary programmers get the things everybody agrees they should be able to do because we're just arguing about how those things work, not whether they should be possible.
Without this constraint, such proposals tend to wander off, each showing how they're ideally suited for solving a problem they came up with, in a context they chose, using methods they prefer, and so illuminating nothing.
A Try operator, perhaps written ?? has been proposed for C++ 26. Even if it's agreed that C++ wants this feature, you can expect years of arguing about exactly how it should work. Rust got its own Try operator ? many years ago. But the conceptual underpinning for this operator (now as the core::ops::Try trait), is still unstable and has actually been re-designed twice in that time. Ordinary Rust programmers don't need to care, they got a working operator, and they'll continue to have a working operator, only the people who care deeply about this need to spend time discussing the finer details of how that operator should be implemented.
- The problem is somewhat underspecified. There are lots of degrees of freedom—what delimiters you support, what character encodings you support, what inputs to accept (numeric vs. names), how exactly to deal with flags, etc. These make a generic solution more involved. It's in some sense a more complex version of the problem of number parsing, which has had quite a long journey and is still not entirely ergonomic in C++. (Even std::from_chars only came out in C++17, for example.)
- Lack of more general reflection capabilities, especially ones that provide string metadata, especially at compile-time. Given reflection isn't coming in C++23, it might be a while before we get support on this front.
