Would anyone like to explain in text form how this works? I've got as far as the use of <{ meaning to run at compile time, so the whole thing is going to be one of those template metaprogramming stunts.
Funnily enough, sufficiently enough of C++ is constexpr-able that it was the driving force for compile-time reflection in C++[1], which is not unlike what the author has done.
Although the new syntax is much more readable than what the author chose to do with expression templates, it's still annoying, as is much of C++. But I still like it, so I am decidedly Stockholmed.
[1]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p29...
As to why, I can't pretend to know the author mind, but I suspect they did it because they could, the project itself is the objective.