220 26389 <84e66a09-6750-4968-856e-a0db36da6eb8@isocpp.org> article Path: news.gmane.org!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: template Date: Sat, 25 Jun 2016 12:00:19 -0700 (PDT) Lines: 167 Approved: news@gmane.org Message-ID: <84e66a09-6750-4968-856e-a0db36da6eb8@isocpp.org> References: <58413fd1-653d-4171-a250-baa99c0a597b@isocpp.org> <2308f718-9fcb-445f-974c-9acc9c0aa605@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_3070_969028084.1466881219333" X-Trace: ger.gmane.org 1466881225 4024 80.91.229.3 (25 Jun 2016 19:00:25 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 25 Jun 2016 19:00:25 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBRFJXO5QKGQE6KYNPHY@isocpp.org Sat Jun 25 21:00:25 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ob0-f198.google.com ([209.85.214.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1bGsoY-0000SF-1n for gclcip-std-proposals@m.gmane.org; Sat, 25 Jun 2016 21:00:22 +0200 Original-Received: by mail-ob0-f198.google.com with SMTP id fq2sf242629469obb.2 for ; Sat, 25 Jun 2016 12:00:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id:in-reply-to:references:subject:mime-version :x-original-sender:reply-to:precedence:mailing-list:list-id :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=uW/coB93z9fkyL04HU0XmgvX86JniHcy/RHI67iSt0k=; b=c5v4bgSd3DxZdtUsNLDCziwsAx5CJzH7CZwzRWaM2+wUwxIinPTMgVfMS8Opsb/bMA xKJ3426SUwToVJL/fBBNZg7TMrO+UyzIAzvyF9CaXr5vBXzB1UvuXsCvoCNbyyrseuy2 34IdyGwgmV2laPNn2+4/XGUJ92ggstftwkrKwSW9oZPqt/5x/k8i+KtbtBt1ZIqJ9dYO f9LpCfCStRC4bqbVLOs3idNV/IXvYqjWsh6niHCnY/M1TNTOtJkErVuWme46ls7iw3kM nf4LW+2fGRnFf40nwWFyvvSqwHZFm/pPQqEU3hfdNH+veW49Fn1YZ9efajszJqRSspJY FV2A== 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 :x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=uW/coB93z9fkyL04HU0XmgvX86JniHcy/RHI67iSt0k=; b=dkqhF18XAnXbic5BwJloh+JC+k9N5wnobB6qRRn7WpEZO7uUFPE5oujXuY5i4Z7CF+ ZMMwN9CT/zT50FNUT1j1WStpJUuzVv763T2NU421uOZqhXr4grFdZWZP7yxruGsYvAvZ 1pv3n6Y6jWJAVcQTKr62UcNNEglxE8HkTzu9MDbu9sitBMAjX1xl6jD+yUFmRPjkK4sm HwBaGoVR+Thck4C8tXYo0PsC4rxI4y1lU2qSxU7Be22HYR7UvIyhRKcW+z9q8DT5u+L0 HISUWCsIAhVYILdPIIySt6NK7bGyhwt1tEyl6Mgr+Jp+yLwvXBpaF07wTrYl5tAR7n6R y0wg== 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:x-spam-checked-in-group:list-post:list-help :list-archive:list-subscribe:list-unsubscribe; bh=uW/coB93z9fkyL04HU0XmgvX86JniHcy/RHI67iSt0k=; b=YHxItJ+/UAHV2NxkxxS2vG0a7OxNMZIJHSBYOiROt6XHlVoUnhFAhRpBnbH3Vf6Co0 ufiw7tcfje51OcOzYiZY40bdVRUlTdLTE07NbMylsKhoMXuQDaw2KZ6g1MnYz6t6Gdyq ndY6mPhWS5jhAcMqzwEb+W2B+jtDaqam6Apx4cL+iaSNuQqm1CgJAlcysjwjuZ3JXgue 9sbLQLCOlvJIv8D8NXxDZSS0XA61Z7zC5HkEnoesI+Z6elh38a5TZevsAipW6oFI6SEr 2y/WkG/wql4xi5fgjUtz0TZbNIBdMLtzQi4g/7J12GnxApvnZuciWdP3foAczkaR62lC Hv7g== X-Gm-Message-State: ALyK8tKUswt5agvV6UHsR1b54WLqHWutYUf/IIMw55V4QqPgJ9Sn9AUXi3UGfyl7TLdUuw== X-Received: by 10.36.73.170 with SMTP id e42mr4150153itd.4.1466881221057; Sat, 25 Jun 2016 12:00:21 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.181.74 with SMTP id e71ls992091iof.27.gmail; Sat, 25 Jun 2016 12:00:20 -0700 (PDT) X-Received: by 10.36.127.66 with SMTP id r63mr114339itc.2.1466881220196; Sat, 25 Jun 2016 12:00:20 -0700 (PDT) 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-Spam-Checked-In-Group: std-proposals@isocpp.org 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:26389 Archived-At: ------=_Part_3070_969028084.1466881219333 Content-Type: multipart/alternative; boundary="----=_Part_3071_1021894798.1466881219334" ------=_Part_3071_1021894798.1466881219334 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Saturday, June 25, 2016 at 2:25:38 PM UTC-4, S.B. wrote: > > On Sunday, June 26, 2016 at 1:56:44 AM UTC+8, Nicol Bolas wrote: >> >> On Saturday, June 25, 2016 at 12:14:28 PM UTC-4, Guillaume Racicot wrote= : >>> >>> After reading P0127R1=20 >>> ,= =20 >>> I wondered if auto& as a template parameter is be possible too. It woul= d=20 >>> allow things like this: >>> >>> template >>> struct Foo { >>> void display() { >>> std::cout << "value: " << thing << " address: " << &thing << st= d >>> ::endl; >>> } >>> }; >>> >>> extern int i; >>> >>> Foo foo; >>> >>> Is this thing already possible in the current proposal? >>> >> >> No. The paper merely adds deduction of the type of non-type template=20 >> parameters based on the value passed. It does not change what valid=20 >> non-type template parameters can be. >> >> You couldn't do `template` before, so you can't do it now.=20 >> > > We *could *do `template` before. > > N4594 =C2=A7 14.1[temp.param]p4 > 4 A non-type template-parameter shall have one of the following=20 > (optionally cv-quali=EF=AC=81ed) types: > =E2=80=94 (4.1) integral or enumeration type, > =E2=80=94 (4.2) pointer to object or pointer to function, > *=E2=80=94 (4.3) lvalue reference to object or lvalue reference to functi= on,* > =E2=80=94 (4.4) pointer to member, > =E2=80=94 (4.5) std::nullptr_t. > >> You can make it a pointer if you want, but that would require doing=20 >> `Foo<*i>`. >> > .... I don't know how I didn't see that the first time I read it. In which case, `auto&` ought to work. --=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/84e66a09-6750-4968-856e-a0db36da6eb8%40isocpp.or= g. ------=_Part_3071_1021894798.1466881219334 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Saturday, June 25, 2016 at 2:25:38 PM UTC-4, S.B. wrote= :
On Sunday, J= une 26, 2016 at 1:56:44 AM UTC+8, Nicol Bolas wrote:
On Saturday, June 25, 2016 at 12:14:28 PM= UTC-4, Guillaume Racicot wrote:
After reading=C2=A0P0127R1, I wondered if auto& as a template= parameter is be possible too. It would allow things like this:

templ= ate<= auto& thing>
struct Foo {=
=C2=A0 =C2=A0 void display() {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 std::cout << "value: " << thing <= /span><<= " address: " << &thing << std::endl;
=C2=A0 =C2=A0 }<= /span>
};

e= xtern i= nt i;

F= oo<i> foo;
<= br>
Is this thing already possible in the current proposal?
=

No. The paper merely adds deduction of the type= of non-type template parameters based on the value passed. It does not cha= nge what valid non-type template parameters can be.

You couldn't= do `template<int &i>`=C2=A0 before, so you can't do it now. =

We could do `template<int &= i>` before.

N4594 =C2=A7 14.1[temp.param]p4
4 A non-type templ= ate-parameter shall have one of the following (optionally cv-quali=EF=AC=81= ed) types:
=E2=80=94 (4.1) integral or enumeration type,
=E2=80=94 (4= ..2) pointer to object or pointer to function,
=E2=80=94 (4.3) lvalue = reference to object or lvalue reference to function,
=E2=80=94 (4.4)= pointer to member,
=E2=80=94 (4.5) std::nullptr_t.
You can make it a pointe= r if you want, but that would require doing `Foo<*i>`.

... I don't know how I didn&#= 39;t see that the first time I read it.

In which case, `auto&` o= ught to work.

--
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To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/84e66a09-6750-4968-856e-a0db36da6eb8= %40isocpp.org.
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