220 8748 article Path: news.gmane.org!not-for-mail From: =?ISO-8859-1?Q?David_Rodr=EDguez_Ibeas?= Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Templetized namespaces Date: Tue, 21 Jan 2014 17:16:58 -0500 Lines: 234 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=001a11c204f2eaf18e04f0825d44 X-Trace: ger.gmane.org 1390342614 9873 80.91.229.3 (21 Jan 2014 22:16:54 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 21 Jan 2014 22:16:54 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDIIVO6GQULBBW7D7OLAKGQEJMGZBFA@isocpp.org Tue Jan 21 23:17:02 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oa0-f72.google.com ([209.85.219.72]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1W5jcz-000526-7w for gclcip-std-proposals@m.gmane.org; Tue, 21 Jan 2014 23:17:01 +0100 Original-Received: by mail-oa0-f72.google.com with SMTP id i4sf10876810oah.7 for ; Tue, 21 Jan 2014 14:17:00 -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:sender: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=1t5VmpoFxfUNLG0uKq0oLI7CXD3+K5pbW1v8IjfQofw=; b=Qr4SjMpiI8GjXwb3dq3ghwmdxlOKc0IxY9fla54RNSfxTwag8nFuCmqcwp9Wyxau5M k6PlDxqfhrVAxUmEK2VW33OTyZdevL1UJp6x4KZVQTBUZferAuZ4igDmqnt/6OedRKur p5CjtdqCn8djGN1NSO/uKLamOq/J2xe62a281VaThy8WfrJM/ZTCYCboD9osnAXTbg3i TDuH/PvlmIwkXllvXZqLhXfRO2MtP4KNfEsjSmF7g/DRLOdlVAhIyiCr772kU9+iZ7wV rn65ZTM4LXnTrUyAWrYkd+LY+1aEdgSyHp2gm8caOEhvYGs5IXFlu65cKRJscOOH6pnY OQcA== X-Gm-Message-State: ALoCoQlDNGMKSEm1JL1GO+Krj1c7Lj0Q4PmiRnKPijEFvygIC6q4TKw66wlxJU20m2yhvkL5vJpJ X-Received: by 10.42.51.141 with SMTP id e13mr3670566icg.28.1390342620262; Tue, 21 Jan 2014 14:17:00 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.42.138 with SMTP id c10ls1343372qga.62.gmail; Tue, 21 Jan 2014 14:16:59 -0800 (PST) X-Received: by 10.236.118.201 with SMTP id l49mr16006218yhh.78.1390342619451; Tue, 21 Jan 2014 14:16:59 -0800 (PST) Original-Received: from mail-ob0-x236.google.com (mail-ob0-x236.google.com [2607:f8b0:4003:c01::236]) by mx.google.com with ESMTPS id 21si5444919yhx.106.2014.01.21.14.16.59 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 21 Jan 2014 14:16:59 -0800 (PST) Received-SPF: pass (google.com: domain of dribeas@gmail.com designates 2607:f8b0:4003:c01::236 as permitted sender) client-ip=2607:f8b0:4003:c01::236; Original-Received: by mail-ob0-f182.google.com with SMTP id wm4so3947053obc.41 for ; Tue, 21 Jan 2014 14:16:59 -0800 (PST) X-Received: by 10.182.243.161 with SMTP id wz1mr22995630obc.10.1390342618933; Tue, 21 Jan 2014 14:16:58 -0800 (PST) Original-Sender: dribeas@gmail.com Original-Received: by 10.182.117.133 with HTTP; Tue, 21 Jan 2014 14:16:58 -0800 (PST) In-Reply-To: <4cfc2db6-97da-4750-9296-5aaaa3475014@isocpp.org> X-Original-Sender: dibeas@ieee.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of dribeas@gmail.com designates 2607:f8b0:4003:c01::236 as permitted sender) smtp.mail=dribeas@gmail.com; dkim=pass header.i=@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:8748 Archived-At: --001a11c204f2eaf18e04f0825d44 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable What are the shortcomings of using a class template as a poor-man's template? I imagine that the first one is that it must be defined in a single header, so if the amount of code used internally is large enough it could make it hard to maintain.The syntax looks like a using-directive, do you also wish for the lookup changes associated with it? I imagine this to be the case, right? Can you use the same library in one program with different template arguments? Can you provide a small code sample with how it would look like? On Sun, Jan 19, 2014 at 1:16 PM, Andrew Tomazos wr= ote: > Namespaces differ from classes in that they can be split within 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 are > logically merged into one (the first is called the original, the followin= g > 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 wh= at > 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. > > 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 librar= y >> 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 suffice >> 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 >> 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 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 ---=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/. --001a11c204f2eaf18e04f0825d44 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
What are the shortcomings of using a class template as a p= oor-man's template?

I imagine that the first one is = that it must be defined in a single header, so if the amount of code used i= nternally is large enough it could make it hard to maintain.The syntax look= s like a using-directive, do you also wish for the lookup changes associate= d with it? I imagine this to be the case, right? Can you use the same libra= ry in one program with different template arguments?

Can you provide a small code sample with how it would l= ook like?=C2=A0


On Sun, Jan 19, 2014 at 1:16 PM, Andrew Tomazos <a= ndrewtomazos@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.

On Sunday, January 19, 2014 6:26= :57 PM UTC+1, dgutson . wrote:
Hi.

=C2=A0 =C2=A0I found a number of situations where th= e ability to templetize namespaces would be very useful.

My latest use case is this: I'm writing a library that is config= ured 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 library i= s tuned with some integers (some of then related to redundancy due to ioniz= ing 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.

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/.

--
 
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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>.
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