Comment by Yoric
2 days ago
> There are a few really amazing things which have been achieved in C++ like fmt, a compile time checked, userspace library for arbitrarily formatting variadic generic parameters.
Anecdotal, but that's hardly unique to C++. So even if C++ were to disappear overnight (which we all agree won't happen), this wouldn't be a burning-library-of-Alexandria moment.
Well. What other examples of this feat are you thinking of?
To me the things which come to mind are either compiler magic (e.g. C printf) or they rely on RTTI (e.g. Odin and similar C-like languages) and neither of those is what fmt does, they're "cheating" in some sense that actually matters.
I co-implemented this in OCaml ~20 years ago, using no compiler magic (it did use a macro). Pretty sure that I've seen the equivalent in Haskell, too, and in variants of Scheme. Zig has it, too. And while, as you mention, the Rust implementation does use compiler magic, I'm pretty sure that it could be implemented as a macro, just more slowly.
etc.
(sorry, it wasn't you who mentioned it, but it was a good remark nevertheless :) )
https://doc.rust-lang.org/std/macro.format.html
https://zig.guide/standard-library/formatting/
Rust is an example of "compiler magic" in this case.
You're right about Zig, and reading the source [1] I'm still kind of impressed how unified they made comptime / runtime.
[1]: https://github.com/ziglang/zig/blob/32a1aabff78234b428234189...