On Tue, Oct 22, 2024 at 6:15 PM Herb Sutter via SG7 <sg7_at_[hidden]>
wrote:

> Thanks Bengt,
>
>
>
> Yes, the syntax in current P0707 is mainly just to be following what SG7
> last directed. Example:
>
>
>
> // Current P0707, per SG7’s last direction
>
> class(interface) IFoo { … };
>
>
>
> But now that we have @, I agree with Bengt that
>
>
>
> @interface class IFoo { … };
>

There are a handful of Objective-c keywords that start with @.
@interface happens
to be one of them


>
>
> is both
>
>
>
> a) cleaner (fun fact: it’s exactly my original P0707R0 proposed syntax and
> C++/CLI syntax, adding only the @ which I agree makes a big difference for
> parsing and legibility), and
>
>
>
> b) more generalizable in the future to functions (as Bengt mentions), and
> this is definitely intended… two canonical examples are
>
>
>
> @pure int f(int a, int b) { … }
>
> - example of a consteval function that could reflect on the body of f
> to enforce that the return value depends only on the parameters
>
>
>
> @autodiff double f(double d) { … }
>
> - example of a consteval function that could additionally generate the
> first derivative of f as f_prime (or d_f or whatever)
>
>
>
> The function metafunctions are also useful, not yet proposed in P0707, but
> which I intend to work on in cppfront this winter. I have a potential
> volunteer to try to prototype the latter example (autodiff) in C++ which
> has long been something that would have been useful for programmers in the
> ML and AI spaces
>
>
>
> Herb
>
>
>
>
>
> *From:* SG7 <sg7-bounces_at_[hidden]> *On Behalf Of *Bengt
> Gustafsson via SG7
> *Sent:* Monday, October 21, 2024 2:19 PM
> *To:* sg7_at_[hidden]
> *Cc:* Bengt Gustafsson <bengt.gustafsson_at_[hidden]>
> *Subject:* [isocpp-sg7] Fwd: P0707
>
>
>
> Hi all,
>
> I suggested to Herb that P0707 should use the decorator syntax from Python
> instead of the inheritance syntax from Python. I think this would cause
> less confusion as the semantics seems to be exactly the same as Python
> decorators, modulo the consteval part of it of course. This decorator
> syntax could then be applied in various places where you may want to modify
> something before actually adding it to the program.
>
> Our conversation is below.
>
> Bengt
>
>
> -------- Forwarded Message --------
>
> *Subject: *
>
> RE: P0707
>
> *Date: *
>
> Sat, 19 Oct 2024 16:10:05 -0700
>
> *From: *
>
> Herb Sutter <herb.sutter_at_[hidden]> <herb.sutter_at_[hidden]>
>
> *To: *
>
> 'Bengt Gustafsson' <bengt.gustafsson_at_[hidden]>
> <bengt.gustafsson_at_[hidden]>
>
>
>
>
> Hi Bengt,
>
>
>
> The reason I'm currently using class(decorator) is only because that's
> what SG7 last recommended.
>
>
>
> I like that, and it did cross my mind when we added @. It's similar to
> what I use in Cpp2:
>
> MyClass: @decorator type = { }
>
>
>
> I probably should mention it -- I'll add it to rNext of the paper. Thanks!
>
>
>
> Herb
>
>
>
> P.S.: Would you like to repeat your feedback to the SG7 reflector? I think
> it's a great suggestion.
>
>
>
>
>
>
>
> > -----Original Message-----
>
> > From: Bengt Gustafsson <bengt.gustafsson_at_[hidden]>
> <bengt.gustafsson_at_[hidden]>
>
> > Sent: Saturday, October 19, 2024 2:08 PM
>
> > To: Herb Sutter <herb.sutter_at_[hidden]> <herb.sutter_at_[hidden]>
>
> > Subject: P0707
>
> >
>
> > Hi Herb,
>
> >
>
> > why not adopt the
>
> >
>
> > @decorator class MyClass {};
>
> >
>
> > syntax from Python?
>
> >
>
> > We just added the @ character and as far as I can see the semantics is
> exactly
>
> > the same as the Python counterpart.
>
> >
>
> > This opens up for allowing decorators on functions and in the future
> maybe
>
> > other constructs with the same (rather well-known) syntax. Or maybe even
> a
>
> > blanket allowance: Wherever you can put ^^ before a contruct you can put
>
> > @function-name instead and let the consteval function adjust the
> contents of
>
> > the following entity.
>
> >
>
> > As long as we haven't used @ for something else there should be no
> parsing
>
> > issues. I can imagine that someone wants @ to be an identifier character
> but I
>
> > haven't seen a proposal for this.
>
> >
>
> > Bengt
>
> >
>
> >
>
> > --
>
> > Bengt Gustafsson
>
>
> --
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