167. Kona, C++26, Contracts, Reflection, Cpp2
With Gianluca Delfino and other colleagues. Reddit thread.
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WG21 Kona meeting, November 2023
- Inbal Levy on Reddit
- Herb Sutter
- Timur Doumler on Reddit
- The Reddit thread doesn’t sound convinced.
From Twitter:
WG21 meeting in Kona is over. SG21 approved our paper with a new Contracts syntax: https://wg21.link/p2961r2
The double square brackets are gone, contract checks are now spelled like this:
int f(int x) pre (x > 0) post (r: r > x) { contract_assert(i > 0); return x + i; }
The natural syntax has won apparently, but contract_assert, seriously? Reddit thread on a possible solution.
From Herb Sutter’s talk:
The attribute-like syntax would have stood out better IMHO, but whatever. As long as Contracts are in C++26…
Also: REFLECTION!
Pattern matching: current target is C++29! <sadface>
From Inbal Levy’s Reddit post comments:
P2971R1: Implication for C++ "There was mild opposition and many neutrals, but also significant interest from a small but vocal set of people." Ok vocal minority, return with your next proposal, but just don’t steal ⇒ for your niche purpose rather than something more valuable and common like a terse lambda many have asked for (and many more have asked for that than have ever asked for implication). ↑
Hear hear!
WG21 October mailing
Paper: std::optional<T&>
P2988R0 by Steve Downey and Peter Sommerlad
We propose to fix a hole intentionally left in std::optional: An optional over a reference such that the post condition on assignment is independent of the engaged state, always producing a rebound reference, and assigning a U to a T is disallowed by static_assert if a U can not be bound to a T&.
Paper: Unified function call syntax (UFCS)
P3021R0 by Herb Sutter
Paper: C++ Should Be C++
P3023R0 by David Sankel (Adobe)
Video: Bjarne Stroustrup - Delivering Safe C++ (CppCon 2023)
A new iteration of the talk discussed previously.
Concrete suggestions for initial Profiles, by Bjarne Stroustrup
Video: Herb Sutter - Cooperative C++ Evolution - Toward a TypeScript for C++ (CppCon 2023)
"Safety for C++ 50x, simplicity for C++ 10x". Round numbers in slogans are a red flag for me, but OK.
Asking the audience: "How many of you would be interested in seeing C++ get significantly simpler and type/memory safer?" is a bit cheap. I’m not a fan of this style of presentation. Especially given that Herb’s "solution" is not actually C++ as such.
That Beetles song again, <eyeroll>. "All you need is class". jfc
"This is pure 100% C++." Proceeds to show non-C++ code, often invoking Bjarne’s name for validation (?).
"Swift is a TypeScript for Objective-C" — WHAT.
Says it’s just a personal experiment, then tells the audience that "the TypeScript way" (Cpp2) is the only way forward for C++ "because people are telling us gradual evolution is not good enough".
Sorry, I shouldn’t be so pessimistic and cynical. It’s easy to criticise without doing the actual work. Cpp2 could be our future. Or Herb could be trailblazing actual new C++ features, like the above UFCS.
But the whole talk feels like an ad.
Stroustrup’s keynote - specifically the last point in the slide where it mentions that successor languages are welcome, but they’re not C++ is relevant here. No matter how much you try and sugarcoat it as a "TypeScript for C++". ↑
How are you doing?
Of course, the proper British way is to always reply, "I’m good, thanks".