buildit VS pfr

The repository also has other samples which demonstrate code generation besides just loop unrolling. If you look at - https://github.com/BuildIt-lang/buildit/blob/master/samples/sample17.cpp and its corresponding output - https://github.com/BuildIt-lang/buildit/blob/master/samples/outputs/sample17 we have an example where you can write an interpreter for a simple language and BuildIt can turn it into a compiler. While this result is not new, in our opinion we make it considerably easy. Specifically we allow side effects on static variables inside control flow dependent on dynamic expressions. The outcome of this might not be obvious, but this allows you to, for example create nested loops which were not there in the original program but were present in the language input (BrainFuck in this case) that you were trying to interpret.

This single feature opens a world of new possiblities. For example, it makes implementing "getting the number of fields" trivial. Furthrmore, and much more importantly, it enables turning a struct into a tuple. Currently, this can only be done by enumerating cases (therefore it's not fully generic), as with Boost PFR. By the way, PFR greatly simplifies our codebases, especially for parts with serialization and/or reflection.

The code is relatively short and can be groked with a few coffees: https://github.com/boostorg/pfr/tree/develop/include/boost/pfr ; if you're using C++17 it uses a binary search (https://github.com/boostorg/pfr/blob/develop/include/boost/pfr/detail/fields_count.hpp) to count the number of fields in a struct, by starting by the observation that a likely majorant on the number of fields in a struct is sizeof(the struct) * CHAR_BIT, assuming not too many [[no_unique_address]] tomfooleries. Then once this count is known it's possible to simply map them as a tuple through sheer brute force and destructuring: https://github.com/boostorg/pfr/blob/develop/include/boost/pfr/detail/core17_generated.hpp

I wonder if the c++ approach of boost.pfr would be portable to rust ? It allows reflection on aggregates without needing to annotate anything: https://github.com/boostorg/pfr

It is an 'interesting' meta-programming problem though (wasted many weeks on it myself, fixed a small gcc bug - a 'uniform init' edge case and filed an issue with magic_get Reflecting array members of aggregate structs).