220 31264 <762243ed-0c31-461d-b6fd-fdb8759857b2@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: P0534: call/cc, type safety and exceptions Date: Wed, 1 Mar 2017 08:50:46 -0800 (PST) Lines: 95 Approved: news@gmane.org Message-ID: <762243ed-0c31-461d-b6fd-fdb8759857b2@isocpp.org> References: <3a57e294-7254-4358-828d-c9f7757f5295@isocpp.org> <4e6c13b2-4286-4df8-989b-97cbf3bf1cc7@isocpp.org> <312d04a6-8b20-4bf5-8357-507ba9938e84@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_10812_899290570.1488387046389" X-Trace: blaine.gmane.org 1488387056 20428 195.159.176.226 (1 Mar 2017 16:50:56 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 1 Mar 2017 16:50:56 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBZ7X3PCQKGQE5MHXOQQ@isocpp.org Wed Mar 01 17:50:51 2017 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f71.google.com ([209.85.218.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1cj7Sc-0003vg-IV for gclcip-std-proposals@m.gmane.org; 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Wed, 01 Mar 2017 08:50:48 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.26.78 with SMTP id u14ls4934353otu.27.gmail; Wed, 01 Mar 2017 08:50:46 -0800 (PST) X-Received: by 10.157.41.152 with SMTP id n24mr1129465otb.0.1488387046914; Wed, 01 Mar 2017 08:50:46 -0800 (PST) In-Reply-To: X-Original-Sender: jmckesson@gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:31264 Archived-At: ------=_Part_10812_899290570.1488387046389 Content-Type: multipart/alternative; boundary="----=_Part_10813_823472932.1488387046389" ------=_Part_10813_823472932.1488387046389 Content-Type: text/plain; charset=UTF-8 On Wednesday, March 1, 2017 at 10:48:40 AM UTC-5, Giovanni Piero Deretta wrote: > > On Wednesday, March 1, 2017 at 3:38:13 PM UTC, Nicol Bolas wrote: > [...] > >> >> So we need the safe mechanism, and we need it shipped with the system. >> But that should not be the *only* way; the lower-level form should still >> exist. >> >> Now, maybe the type-safe version should be the *default*, so that if you >> want the lower-level, unsafe API, we can clearly see that safety is being >> sacrificed. So `callcc/continuation` would naturally be type-safe, with >> `unsafe_callcc/unsafe_continuation` being not type safe. >> > > we are in agreement then, I just want to point out that, given a type safe > std::continuation implementation, the unsafe variant would simply be > std::continuation, while the dynamic variant would be > continuation, given a suitable implementation of any_ptr. > I don't think you understood what I meant when I said "type safe". I specifically *don't* mean that the continuation has a static and typed set of parameters. What I mean is that getting the parameter back is type-checked and therefore safe. But it's a *runtime* check, not a compile-time check. This prevents compile-time tight coupling while still having safety on the receiving end. -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/762243ed-0c31-461d-b6fd-fdb8759857b2%40isocpp.org. ------=_Part_10813_823472932.1488387046389 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Wednesday, March 1, 2017 at 10:48:40 AM UTC-5, = Giovanni Piero Deretta wrote:
<= div dir=3D"ltr">On Wednesday, March 1, 2017 at 3:38:13 PM UTC, Nicol Bolas = wrote:
[...]

So we need the safe mechanism, and we need it shipped with the sy= stem. But that should not be the only way; the lower-level form shou= ld still exist.

Now, maybe the type-safe version should be the de= fault, so that if you want the lower-level, unsafe API, we can clearly = see that safety is being sacrificed. So `callcc/continuation` would natural= ly be type-safe, with `unsafe_callcc/unsafe_continuation` being not ty= pe safe.

we are in agreement then, I j= ust want to point out that, given a type safe std::continuation<T> im= plementation, the unsafe variant would simply be std::continuation<void*= >, while the dynamic variant would be continuation<std::any_ptr>, = given a suitable implementation of any_ptr.

I don't think you understood what I meant when I said "type = safe". I specifically don't mean that the continuation has = a static and typed set of parameters. What I mean is that getting the param= eter back is type-checked and therefore safe. But it's a runtime= check, not a compile-time check.

This prevents compile-time tight c= oupling while still having safety on the receiving end.

--
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