220 8811 article Path: news.gmane.org!not-for-mail From: "dgutson ." Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Templetized namespaces Date: Sat, 25 Jan 2014 22:48:51 -0200 Lines: 326 Approved: news@gmane.org Message-ID: References: <4cfc2db6-97da-4750-9296-5aaaa3475014@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary=bcaec52beba574203504f0d4f4c0 X-Trace: ger.gmane.org 1390697327 15704 80.91.229.3 (26 Jan 2014 00:48:47 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 26 Jan 2014 00:48:47 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDE3NBMV6UFBB5VWSGLQKGQEBPF4XQI@isocpp.org Sun Jan 26 01:48:55 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-lb0-f200.google.com ([209.85.217.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1W7DuB-00045c-6O for gclcip-std-proposals@m.gmane.org; Sun, 26 Jan 2014 01:48:55 +0100 Original-Received: by mail-lb0-f200.google.com with SMTP id c11sf8954703lbj.7 for ; Sat, 25 Jan 2014 16:48:54 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=xZ1sZ9nCOuKr13fMyHUKj0XTUv1KQ3xqBrJ/sNb6VRQ=; b=mwS33ojbDdgXRa5RLmPmYJQLloMyIPRWSPcTCf9zQtJDlTeXBx1BTc/bfszOA97nlX l1u+B8GC+i47ei3IJNxwhRhPa7QVk3lHTLpL+JyFawQUPGL/O8e8Caaxl3oaSi6vBO5Z MZw91INzE+91WbVhZk8xnq5nPDXGIzup2/PAuOtFKPwOi93Fm6XfYezO+o5ZqYkLvytt wuQlYms8+rQms1L0eJhoxyAkV6AHqHUcT6NMWbPTHUwSrIpwjIgLpZSPZXa9mnTUlNLt kiO9OGJdukH6lu7psw1a3O+3S8Nf/3gRiRJn+/21BjF+JNAPlImLgVFdrAxFaHtaKM0y DMFQ== X-Gm-Message-State: ALoCoQl7GXfY59HIVNVfM+Ux9cdxLCO+xEIhKoLPZ/+WyBGra/Ut3aLapMvNG/lFGvfpiDOthG8w X-Received: by 10.205.105.2 with SMTP id do2mr5788774bkc.1.1390697334462; Sat, 25 Jan 2014 16:48:54 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.20.100 with SMTP id m4ls668819wie.38.gmail; Sat, 25 Jan 2014 16:48:53 -0800 (PST) X-Received: by 10.204.114.12 with SMTP id c12mr12753138bkq.61.1390697333762; Sat, 25 Jan 2014 16:48:53 -0800 (PST) Original-Received: from mail-pb0-x231.google.com (mail-pb0-x231.google.com [2607:f8b0:400e:c01::231]) by mx.google.com with ESMTPS id ou7si8542354bkb.304.2014.01.25.16.48.53 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 25 Jan 2014 16:48:53 -0800 (PST) Received-SPF: pass (google.com: domain of danielgutson@gmail.com designates 2607:f8b0:400e:c01::231 as permitted sender) client-ip=2607:f8b0:400e:c01::231; Original-Received: by mail-pb0-f49.google.com with SMTP id up15so4576586pbc.36 for ; Sat, 25 Jan 2014 16:48:51 -0800 (PST) X-Received: by 10.66.27.107 with SMTP id s11mr22551555pag.64.1390697331825; Sat, 25 Jan 2014 16:48:51 -0800 (PST) Original-Received: by 10.70.78.200 with HTTP; Sat, 25 Jan 2014 16:48:51 -0800 (PST) In-Reply-To: X-Original-Sender: danielgutson@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of danielgutson@gmail.com designates 2607:f8b0:400e:c01::231 as permitted sender) smtp.mail=danielgutson@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=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:8811 Archived-At: --bcaec52beba574203504f0d4f4c0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Tue, Jan 21, 2014 at 8:54 PM, Richard Smith wrote= : > On Sun, Jan 19, 2014 at 10:16 AM, Andrew Tomazos wrote: > >> Namespaces differ from classes in that they can be split within and >> amongst translation units. The definition of a namespace is not require= d >> to be the same in different translation units. Multiple namespace >> definitions of the same namespace in the same translation unit are >> logically merged into one (the first is called the original, the followi= ng >> are called extensions). >> >> How do template namespace specialization and template namespace >> instantiation interact with these new properties that are not present in >> other template entities? >> >> Also namespaces can contain the following declarations, whereas classes >> cannot: >> >> explicit-instantiation >> explicit-specialization >> linkage-speci=EF=AC=81cation >> namespace-de=EF=AC=81nition >> attribute-declaration >> asm-de=EF=AC=81nition >> namespace-alias-de=EF=AC=81nition >> using-directive >> opaque-enum-declaration >> >> Now that all these are possible member declarations of a template entity= , >> how are they handled? >> >> Also you need to think about program initialization. The members of a >> namespace have a bunch of rules about when they are initialized and in w= hat >> order. How will these rules interact with template namespace instances? >> >> The best approach for this type of feature would be to put together an >> experimental compiler extension to gcc or clang that implements template >> namespaces. This would shake out all the above issues (and likely more) >> which you could then use as the basis of a proposal. >> > > In addition to the above list, a proposal on this would need to consider > whether namespace templates could support explicit specializations, parti= al > specializations, and explicit instantiations (both for themselves and for > their members). > Maybe funny things could be done with this and template metaprogramming: template namespaces recursively instantiating themselves. However, I'm not sure if new inventions would arise not done before with template classes. > > >> On Sunday, January 19, 2014 6:26:57 PM UTC+1, dgutson . wrote: >>> >>> Hi. >>> >>> I found a number of situations where the ability to templetize >>> namespaces would be very useful. >>> >>> My latest use case is this: I'm writing a library that is configured >>> through a number of (non-type) template arguments. Such configuration >>> affects to all the classes of the library. To be more specific, it's a >>> fault-tolerant library for the aerospace industry where the whole libra= ry >>> is tuned with some integers (some of then related to redundancy due to >>> ionizing radiation). >>> >>> The most natural thing would be to put all the classes in a namespace, >>> and let the namespace be templetized with such arguments. >>> Moreover, a using namespace with the appropriate arguments would suffic= e >>> for all the application. For example: >>> >>> using namespace TheLibrary; >>> >>> I didn't write the proposal yet, since I'd like to get some feedback. >>> >> > I think this feature would have value, and seems worth putting before the > committee. > > >> Thanks, >>> >>> Daniel. >>> >>> ps: The library will be available soon and uses template metaprogrammin= g >>> based on the arguments. >>> >>> >>> -- >>> Who=E2=80=99s got the sweetest disposition? >>> One guess, that=E2=80=99s who? >>> Who=E2=80=99d never, ever start an argument? >>> Who never shows a bit of temperament? >>> Who's never wrong but always right? >>> Who'd never dream of starting a fight? >>> Who get stuck with all the bad luck? >>> >> -- >> >> --- >> You received this message because you are subscribed to the Google Group= s >> "ISO C++ Standard - Future Proposals" group. >> To unsubscribe from this group and stop receiving emails from it, send a= n >> email to std-proposals+unsubscribe@isocpp.org. >> To post to this group, send email to std-proposals@isocpp.org. >> Visit this group at >> http://groups.google.com/a/isocpp.org/group/std-proposals/. >> > > -- > > --- > 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. > Visit this group at > http://groups.google.com/a/isocpp.org/group/std-proposals/. > --=20 Who=E2=80=99s got the sweetest disposition? One guess, that=E2=80=99s who? Who=E2=80=99d never, ever start an argument? Who never shows a bit of temperament? Who's never wrong but always right? Who'd never dream of starting a fight? Who get stuck with all the bad luck? --=20 ---=20 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 e= mail to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposa= ls/. --bcaec52beba574203504f0d4f4c0 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable



On Tue, Jan 21, 2014 at 8:54 PM, Richard Smith &l= t;richard@metafo= o.co.uk> wrote:
=
On Sun, Jan 19, 2014 at 10:16 = AM, Andrew Tomazos <andrewtomazos@gmail.com> wrote:
Namespaces differ from clas= ses in that they can be split within and amongst translation units. =C2=A0T= he definition of a namespace is not required to be the same in different tr= anslation units. =C2=A0Multiple namespace definitions of the same namespace= in the same translation unit are logically merged into one (the first is c= alled the original, the following are called extensions).

How do template namespace specialization and template namesp= ace instantiation interact with these new properties that are not present i= n other template entities?

Also namespaces can con= tain the following declarations, whereas classes cannot:

explicit-instantiation
explicit-spec= ialization
linkage-speci=EF=AC=81cation
namespace-de=EF= =AC=81nition
attribute-declaration
asm-de=EF=AC=81n= ition
namespace-alias-de=EF=AC=81nition
using-directive
o= paque-enum-declaration

Now that all thes= e are possible member declarations of a template entity, how are they handl= ed?

Also you need to think about program initialization. = =C2=A0The members of a namespace have a bunch of rules about when they are = initialized and in what order. =C2=A0How will these rules interact with tem= plate namespace instances?

The best approach for this type of feature would be to = put together an experimental compiler extension to gcc or clang that implem= ents template namespaces. =C2=A0This would shake out all the above issues (= and likely more) which you could then use as the basis of a proposal.

In addition to the above list,= a proposal on this would need to consider whether namespace templates coul= d support explicit specializations, partial specializations, and explicit i= nstantiations (both for themselves and for their members).

Maybe funny things could= be done with this and template metaprogramming: template namespaces recurs= ively instantiating themselves.
However, I'm not sure if new = inventions would arise not done before with template classes.
=C2=A0
=C2=A0
=
On Sunday, January 19, 2014 6:26:57 PM UTC+1, dgutson . wrote:
Hi.

=C2=A0 =C2=A0I found a number of si= tuations where the ability to templetize namespaces would be very useful.

My latest use case is this: I'm writing a libra= ry that is configured through a number of (non-type) template arguments. Su= ch configuration affects to all the classes of the library. To be more spec= ific, it's a fault-tolerant library for the aerospace industry where th= e whole library is tuned with some integers (some of then related to redund= ancy due to ionizing radiation).

The most natural thing would be to put all the classes = in a namespace, and let the namespace be templetized with such arguments.
Moreover, a using namespace with the appropriate arguments would s= uffice for all the application. For example:

=C2=A0 =C2=A0 using namespace TheLibrary<arg1, arg2,= arg3>;

I didn't write the proposal yet, si= nce I'd like to get some feedback.
=

I think this feature would hav= e value, and seems worth putting before the committee.
=C2=A0
Thanks,

=C2=A0 =C2=A0Daniel.

ps: The librar= y will be available soon and uses template metaprogramming based on the arg= uments.


--
Who=E2=80=99s got= the sweetest disposition?
One guess, that=E2=80=99s who?
Who=E2=80=99d never, ever start an argume= nt?
Who never shows a bit of temperament?
Who's never wrong but a= lways right?
Who'd never dream of starting a fight?
Who get stuck= with all the bad luck?=20

--
=C2=A0
---
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
Visit this group at http://groups.google.com/a/isocpp.org/gro= up/std-proposals/.

=

--
=C2=A0
---
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
Visit this group at http://groups.google.com/a/isocpp.org/gro= up/std-proposals/.



--
= Who=E2=80=99s got the sweetest disposition?
One guess, that=E2=80=99s wh= o?
Who=E2=80=99d never, ever start an argument?
Who never shows a bit= of temperament?
Who's never wrong but always right?
Who'd never dream of starting a fight?
Who get stuck with all the ba= d luck?=20

--
 
---
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposals+unsubscribe@isocpp.org.
To post to this group, send email to std-proposals@isocpp.org.
Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/<= /a>.
--bcaec52beba574203504f0d4f4c0-- .