Re:Thriving in a Crowded and Changing World: C++ 2006–2020 [...
by tialaramex on Saturday July 17, 2021 @08:07AM
(#27865233)
There are a few other cute tricks (not all of which were in Rust 1.0) to enable this.
Rust's "raw" way to spell all symbols is clever. Maybe some day my function named weigh will be a problem because of a new "weigh" keyword. Rust gets to add the keyword but still talk about my function in new editions by just spelling the symbol awkwardly, as r#weigh. This forbids Rust from reserving such spellings (e.g. "r#weigh") as keywords themselves, but that would be so ugly nobody would want to do it. Overall the result is Rust 2021 could even make "new" a keyword if it wanted to, and the old code which uses that symbol name everywhere still works, it's just a little clumsy to talk to it from next edition code.
Still, I think it's worth remembering that the edition changes in Rust so far have been much smaller than many changes contemplated for C++ Epochs (or any hypothetical actual C++ feature similar to Vittorio's proposal in spirit).
C++ has a lot of problems, and understandably Epoch proponents want to do stuff like ban implicit narrowing coercions, or change how overflow works. Because of how sprawling C++ is these are surprisingly big changes to the whole language, and I don't think that you could pull off something like that with editions.
I have a hopeful note though. Maybe C++ can inspire a much more powerful tool than editions, somehow enabling backward compatibility for C++ while also allowing new C++ to be written exclusively in Stroustrup's "subset of a superset" that keeps most of C++'s strengths but loses so much baggage like implicit coercions everywhere. If it's possible, the C++ community have the right people.
Rust's "raw" way to spell all symbols is clever. Maybe some day my function named weigh will be a problem because of a new "weigh" keyword. Rust gets to add the keyword but still talk about my function in new editions by just spelling the symbol awkwardly, as r#weigh. This forbids Rust from reserving such spellings (e.g. "r#weigh") as keywords themselves, but that would be so ugly nobody would want to do it. Overall the result is Rust 2021 could even make "new" a keyword if it wanted to, and the old code which uses that symbol name everywhere still works, it's just a little clumsy to talk to it from next edition code.
Still, I think it's worth remembering that the edition changes in Rust so far have been much smaller than many changes contemplated for C++ Epochs (or any hypothetical actual C++ feature similar to Vittorio's proposal in spirit).
C++ has a lot of problems, and understandably Epoch proponents want to do stuff like ban implicit narrowing coercions, or change how overflow works. Because of how sprawling C++ is these are surprisingly big changes to the whole language, and I don't think that you could pull off something like that with editions.
I have a hopeful note though. Maybe C++ can inspire a much more powerful tool than editions, somehow enabling backward compatibility for C++ while also allowing new C++ to be written exclusively in Stroustrup's "subset of a superset" that keeps most of C++'s strengths but loses so much baggage like implicit coercions everywhere. If it's possible, the C++ community have the right people.