220 8691 <4cfc2db6-97da-4750-9296-5aaaa3475014@isocpp.org> article Path: news.gmane.org!not-for-mail From: Andrew Tomazos Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Templetized namespaces Date: Sun, 19 Jan 2014 10:16:23 -0800 (PST) Lines: 173 Approved: news@gmane.org Message-ID: <4cfc2db6-97da-4750-9296-5aaaa3475014@isocpp.org> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_Part_188_9001793.1390155383836" X-Trace: ger.gmane.org 1390155378 17360 80.91.229.3 (19 Jan 2014 18:16:18 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 19 Jan 2014 18:16:18 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBD5KHQXXWYPRB6FM6CLAKGQEEZNL5BA@isocpp.org Sun Jan 19 19:16:26 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vc0-f198.google.com ([209.85.220.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1W4wv3-0007Du-Lj for gclcip-std-proposals@m.gmane.org; Sun, 19 Jan 2014 19:16:25 +0100 Original-Received: by mail-vc0-f198.google.com with SMTP id lf12sf10320399vcb.9 for ; Sun, 19 Jan 2014 10:16:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :list-post:list-help:list-archive:list-subscribe:list-unsubscribe :content-type; bh=kpax2Nl8A4jge+h6EWlX/vpFdaAGBFU/P7LkMl/E6lI=; b=LKyLHTxa9HG+5b/3aEaqcMGSe8PDV+XdUdD3am+t7wYXiriTYHcLaMBhYl+bCRZxzk QveFC0SO8o5VH9/ukoWISw7/+6WG7PCMlDa+4FAELP15ZTSn1aJX2NeafRbmEAfBRuen Q9cWZ5vSxbmwlZYAjDrDv1MhqnSp/vI5iBH/tQ4Jma2aw26khQVNdvLMFrdmgt2Xn3aG 4RFeVqNMe4ZCbgA8DzFunhS8NcFM3iNq3Mmr70OI32VdrSqgLQXsR5y2D+PR0M/D213d LxVVBy3ynp+lz7F8KGvDoXrYv20PxlQDiC5Xv0cuZT4qBrlQ78o4Q+TwiROCJuGqxfwV N65A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:date:from:to:message-id:in-reply-to:references :subject:mime-version:x-original-sender:reply-to:precedence :mailing-list:list-id:list-post:list-help:list-archive :list-subscribe:list-unsubscribe:content-type; bh=kpax2Nl8A4jge+h6EWlX/vpFdaAGBFU/P7LkMl/E6lI=; b=JL2/EVlb7J47joPJ1YiE9sBNATKiclaJSNBimGzPS2ZE1xc5vHHCL/U/WRhcDtIF9B RXrjM2Wk9qwSOL1FPtAE00Wqrpoqrh7dcNAPQwDaBuKOJic63MQc0G4sLtZJ67R7CwDo PHmKHTJbbIrm2xuebz6l97pbxP9se0iGzYlMkaQVe9ZpqMaW9ewYg3ZoUN0PzXw1n6k5 NZ/+j6DgbemkeoVEQTyD1/FbgwSsXbDmaxyxyj2GGryRsVUwgG4wp/vgnqZL24uIc4yQ EpNmCe9lJyDcb+nvPx/RdurCMs7RGGpTF6mbZIubzjbNI8qjjjsGVrm0E10bDtoPXUGr Mv3w== X-Gm-Message-State: ALoCoQmXveszsomU+jbYylTJz/WbaRFXk1YUvYB1bPfnVQz+KfR/uFXVg1o+fpDVJOSrjZDYQy/5 X-Received: by 10.58.23.137 with SMTP id m9mr5088368vef.13.1390155384821; Sun, 19 Jan 2014 10:16:24 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.49.81.102 with SMTP id z6ls1559442qex.97.gmail; Sun, 19 Jan 2014 10:16:24 -0800 (PST) X-Received: by 10.140.95.144 with SMTP id i16mr342127qge.1.1390155384348; Sun, 19 Jan 2014 10:16:24 -0800 (PST) In-Reply-To: X-Original-Sender: andrewtomazos@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:8691 Archived-At: ------=_Part_188_9001793.1390155383836 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Namespaces differ from classes in that they can be split within and amongst= =20 translation units. The definition of a namespace is not required to be the= =20 same in different translation units. Multiple namespace definitions of the= =20 same namespace in the same translation unit are logically merged into one= =20 (the first is called the original, the following are called extensions). How do template namespace specialization and template namespace=20 instantiation interact with these new properties that are not present in=20 other template entities? Also namespaces can contain the following declarations, whereas classes=20 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,= =20 how are they handled? Also you need to think about program initialization. The members of a=20 namespace have a bunch of rules about when they are initialized and in what= =20 order. How will these rules interact with template namespace instances? The best approach for this type of feature would be to put together an=20 experimental compiler extension to gcc or clang that implements template=20 namespaces. This would shake out all the above issues (and likely more)=20 which you could then use as the basis of a proposal. 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=20 > namespaces would be very useful. > > My latest use case is this: I'm writing a library that is configured=20 > through a number of (non-type) template arguments. Such configuration=20 > affects to all the classes of the library. To be more specific, it's a=20 > fault-tolerant library for the aerospace industry where the whole library= =20 > is tuned with some integers (some of then related to redundancy due to=20 > ionizing radiation). > > The most natural thing would be to put all the classes in a namespace, an= d=20 > let the namespace be templetized with such arguments. > Moreover, a using namespace with the appropriate arguments would suffice= =20 > for all the application. For example: > > using namespace TheLibrary; > > I didn't write the proposal yet, since I'd like to get some feedback. > > Thanks, > > Daniel. > > ps: The library will be available soon and uses template metaprogramming= =20 > based on the arguments. > > > --=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 ---=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/. ------=_Part_188_9001793.1390155383836 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Namespaces differ from classes in that they can be split w= ithin and amongst translation units.  The definition of a namespace is= not required to be the same in different translation units.  Multiple= namespace definitions of the same namespace in the same translation unit a= re logically merged into one (the first is called the original, the followi= ng are called extensions).

How do template namespace spe= cialization and template namespace instantiation interact with these new pr= operties that are not present in other template entities?

Also namespaces can contain the following declarations, whereas cla= sses 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 namespa= ce have a bunch of rules about when they are initialized and in what order.=  How will these rules interact with template namespace instances?

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

On Sunday, January 19, 2014 6:26:57 PM UTC+1, dgutson= . wrote:
Hi.<= div>
   I found a number of situations where the ab= ility to templetize namespaces would be very useful.

My latest use case is this: I'm writing a library that is configured thr= ough 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-tolera= nt library for the aerospace industry where the whole library is tuned with= some integers (some of then related to redundancy due to ionizing radiatio= n).

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:

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

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

Thanks,

   Daniel.

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 alway= s right?
Who'd never dream of starting a fight?
Who get stuck with al= l the bad 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>.
------=_Part_188_9001793.1390155383836-- .