220 28137 article Path: news.gmane.org!.POSTED!not-for-mail From: Tom Honermann Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: Implicit function template arguments enabling syntax, an alternative to abbreviated templates Date: Wed, 7 Sep 2016 13:30:48 -0400 Lines: 170 Approved: news@gmane.org Message-ID: References: <627640bf-62bf-491e-bea9-f76eec0033ec@isocpp.org> <0c4a29e2-b327-4957-9120-2fbe623a6ca3@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------5CE8B091D6CEC24C48FB1278" X-Trace: blaine.gmane.org 1473269458 27870 195.159.176.226 (7 Sep 2016 17:30:58 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 7 Sep 2016 17:30:58 +0000 (UTC) User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDBNXSHG6UDBBTE5YG7AKGQE6SHU6LQ@isocpp.org Wed Sep 07 19:30:53 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ua0-f200.google.com ([209.85.217.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bhggV-0006cD-Tz for gclcip-std-proposals@m.gmane.org; Wed, 07 Sep 2016 19:30:52 +0200 Original-Received: by mail-ua0-f200.google.com with SMTP id 71sf41787931uag.0 for ; Wed, 07 Sep 2016 10:30:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:x-original-sender:x-original-authentication-results :reply-to:precedence:mailing-list:list-id:x-spam-checked-in-group :list-post:list-help:list-archive:list-subscribe:list-unsubscribe; bh=UUyMGITAyKJWTrYtJdGNZ9+WkF5qb84zVvbkGtfcnoc=; b=SZtGsHotxRFx9yDBIIaW2nxBdxOSvLhldzUm3HST1Ow9j1dGaJtyROJzatRHc070LW UKI1KreHwxfSOUve0pcMOxFAWIR5bKnziu1OM2mfuCe7KwBRzagadzPe7X/WFcrKdLdY TfvdZxgoZReVzWYPJ2Zu5AvGIbWyXDVSiVHFGL4FI4KJHtepg+duuDX46JlkyPX7J7Js oVN5nCnuLbUapBvZueGcBNImgf7vCFKBmoKVlzoNLov+ZD3aTPSxQ1zSSZbPeBiUOjf5 rp7yJgknLZGkYLFEEul+D9V+a2ar6aLI1ScDjMQ2G1ei0UeRoQdRmcs3hPzRSeyhjKhy yycw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:x-spam-checked-in-group:list-post:list-help:list-archive :list-subscribe:list-unsubscribe; bh=UUyMGITAyKJWTrYtJdGNZ9+WkF5qb84zVvbkGtfcnoc=; b=Kh+D6C2PMCm1QnyZect7/TOvFNXiSO5Rt6JGyWvQus3OWMwtraQd5axugblkw2sbP9 1UFNptN7vS/oTLdTueurpc2fuXEB/MquxKglRjRbRpX6ihFxphqYbELx0PvFDtuPVpxn k4tuUWNEbsRXI0IaFKtjTz5OMwyApu2uwdG0lIwcPZl+Ki90HlmAK3qNqdaWQ08S3afN UNBMkILb+n4G0Yhvut6+sof3zC+0ugEZqHb3234+4/sWrTiSYYBb7m390Ijtvjy2WY7Q zRlZG2OqVhy+2d2Fj5uGbZIwBxA3tGKjNgKEBqOja3gUZKj4Xat+f8aPNZurO3uvgVbL vdNA== X-Gm-Message-State: AE9vXwOwIZiwtlTPSntiSmwXWaYt+I7jBoRz5CSvXJlBvhkitmsrTdyi21gKOVWyBccnZw== X-Received: by 10.237.53.75 with SMTP id b11mr39799749qte.4.1473269452952; Wed, 07 Sep 2016 10:30:52 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.157.62.138 with SMTP id b10ls810630otc.21.gmail; Wed, 07 Sep 2016 10:30:51 -0700 (PDT) X-Received: by 10.200.56.3 with SMTP id q3mr24946466qtb.21.1473269451789; Wed, 07 Sep 2016 10:30:51 -0700 (PDT) Original-Received: from smtp67.iad3a.emailsrvr.com (smtp67.iad3a.emailsrvr.com. [173.203.187.67]) by mx.google.com with ESMTPS id b139si1542227qkc.297.2016.09.07.10.30.51 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 07 Sep 2016 10:30:51 -0700 (PDT) Received-SPF: neutral (google.com: 173.203.187.67 is neither permitted nor denied by best guess record for domain of tom@honermann.net) client-ip=173.203.187.67; Original-Received: from smtp17.relay.iad3a.emailsrvr.com (localhost [127.0.0.1]) by smtp17.relay.iad3a.emailsrvr.com (SMTP Server) with ESMTP id 53AE4A02C7 for ; Wed, 7 Sep 2016 13:30:51 -0400 (EDT) X-Auth-ID: tom@honermann.net Original-Received: by smtp17.relay.iad3a.emailsrvr.com (Authenticated sender: tom-AT-honermann.net) with ESMTPSA id B0AF0A02C3 for ; Wed, 7 Sep 2016 13:30:50 -0400 (EDT) X-Sender-Id: tom@honermann.net Original-Received: from [10.12.197.214] (us02-rap-1.synopsys.com [198.182.60.251]) (using TLSv1.2 with cipher DHE-RSA-AES128-SHA) by 0.0.0.0:587 (trex/5.7.7); Wed, 07 Sep 2016 13:30:51 -0400 In-Reply-To: <0c4a29e2-b327-4957-9120-2fbe623a6ca3@isocpp.org> X-Original-Sender: tom@honermann.net X-Original-Authentication-Results: mx.google.com; spf=neutral (google.com: 173.203.187.67 is neither permitted nor denied by best guess record for domain of tom@honermann.net) smtp.mailfrom=tom@honermann.net 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:28137 Archived-At: This is a multi-part message in MIME format. --------------5CE8B091D6CEC24C48FB1278 Content-Type: text/plain; charset=UTF-8; format=flowed On 9/7/2016 1:13 PM, Ivan G. wrote: > Thanks for the answers! I'll correct the syntax a bit. > > I'm not sure I understand what the point of the `...` part is. > > One of the primary problems (to me) with the fully terse template > function syntax is that it declares a template function without > telling the user that they've done that. So it seems to me that it > is enough to simply use the `template` keyword: > > | > template<> > voidfoo(autox); > | > > I just don't see a real need to have the `...` there, just to say > that the parameter list will also add template arguments. That can > be implicit. > > > AFAIK plain template<> syntax is already used for explicit function > template specializations. Forgive me if I'm wrong, but such a > specialization is not considered a template but rather a function. > > template <..., typename T> > void foo2(T x, auto y) > { > } > > foo2(42, 42); // OK > foo2(42, false); // OK > > If explicit template parameters are allowed for auto arguments, then > they must have some specific order in which they appear in template > argument list. In this case, an ellipsis may be used to adjust their > appearance by placing it in the beginning or even in the middle. The Concepts TS specifies the order for invented template parameters. See N4553 [1] [dcl.fct] 8.3.5 p16-17. Tom. [1]: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4553.pdf -- 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/d31e50f3-4d9a-40e0-009a-17b7cad7f497%40honermann.net. --------------5CE8B091D6CEC24C48FB1278 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On 9/7/2016 1:13 PM, Ivan G. wrote:
Thanks for the answers! I'll correct the syntax a bit.
I'm not sure I understand what the point of the `...` part is.

One of the primary problems (to me) with the fully terse template function syntax is that it declares a template function without telling the user that they've done that. So it seems to me that it is enough to simply use the `template` keyword:

template<>
void foo(auto x);

I just don't see a real need to have the `...` there, just to say that the parameter list will also add template arguments. That can be implicit.

AFAIK plain template<&= gt;=C2=A0syntax is already used for explicit function template specializations. Forgive me if I'm wrong, but such a specialization is not considered a template but rather a function.

template <..., typename T>
void foo2(T x, auto y)
{
}

foo2<int>(42, 42); // OK
foo2<bool, int>(42, false); // OK

If explicit template parameters are allowed for auto arguments, then they must have some specific order in which they appear in template argument list. In this case, an ellipsis may be used to adjust their appearance by placing it in the beginning or even in the middle.

The Concepts TS specifies the order for invented template parameters.=C2=A0 See N4553 [1] [dcl.fct] 8.3.5 p16-17.

Tom.

[1]: http://www.open-std.org/jtc1/sc22/wg= 21/docs/papers/2015/n4553.pdf

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