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Botet Escriba" Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Re: [c++std-core-27216] Re: An implementation of enhanced auto deduction and abbreviated template syntax using Clang Date: Sat, 07 Mar 2015 17:26:28 +0100 Lines: 234 Approved: news@gmane.org Message-ID: <54FB26B4.4050809@wanadoo.fr> References: <54F91983.2020808@stroustrup.com> <54F930C8.30609@coverity.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="------------040008010001080806040309" X-Trace: ger.gmane.org 1425745601 24980 80.91.229.3 (7 Mar 2015 16:26:41 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 7 Mar 2015 16:26:41 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBDH67CONY4PBBNGN5STQKGQEBASAE5Y@isocpp.org Sat Mar 07 17:26:33 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-wi0-f198.google.com ([209.85.212.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1YUHYd-0005T3-1b for gclcip-std-proposals@m.gmane.org; Sat, 07 Mar 2015 17:26:31 +0100 Original-Received: by wivr20 with SMTP id r20sf6392117wiv.0 for ; Sat, 07 Mar 2015 08:26:30 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:message-id:date:from:user-agent:mime-version:to :subject:references:in-reply-to:content-type:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=fNy+cYCTcCBxc/IED5sWhMgv/PmmNlopqUYXQfxgXX0=; b=IodJ6vWeFGY1PkTpCs+dK+WlITtjbw514RGuk97OuBCDDGJN6dyEFSrnhjTB7+pKQ6 ZZSapv5S7n9W9O1oCUEPmIh69VPjPPW0FzGPQ6uNH/5wLG0Zoth1CWWErqtahV0vPOz8 lhBFl2mhtRk5hwFfIuEgeobEwc5+wwJihOg7kUgZA0BHzck9lKEhEcV9iMIG7oiNr2zW HPHEvWRyDiMSs7K+kj3vevWHFG2ULiTvsKKPL4Yv7D55LGAUsjX6INVAdFHEWJQqAN7t 9Jnv9LF1TsCZjM1E3Z6RnqVL1jjNepbi733nCNGS2NJaV4wzgiDm9qCmWEwjpeFE7ZDD qhGw== X-Gm-Message-State: ALoCoQmAyLNrOsNA7Nd1yL+G9tZ71uTeNT/ZhuFYceXQDijxYuj2G0flko6ELtsOfufZi9uEzH0D X-Received: by 10.194.161.194 with SMTP id xu2mr3009423wjb.1.1425745590506; Sat, 07 Mar 2015 08:26:30 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.180.14.9 with SMTP id l9ls281398wic.11.canary; Sat, 07 Mar 2015 08:26:28 -0800 (PST) X-Received: by 10.180.208.74 with SMTP id mc10mr87328114wic.38.1425745588271; Sat, 07 Mar 2015 08:26:28 -0800 (PST) Original-Received: from smtp.smtpout.orange.fr (smtp05.smtpout.orange.fr. [80.12.242.127]) by mx.google.com with ESMTP id ck8si25850570wjb.30.2015.03.07.08.26.28 for ; Sat, 07 Mar 2015 08:26:28 -0800 (PST) Received-SPF: none (google.com: vicente.botet@wanadoo.fr does not designate permitted sender hosts) client-ip=80.12.242.127; Original-Received: from iMac-de-Vicente-Botet-Escriba.local ([2.11.66.123]) by mwinf5d09 with ME id 0gSS1q00S2fZjpN03gSTLi; Sat, 07 Mar 2015 17:26:28 +0100 X-ME-Helo: iMac-de-Vicente-Botet-Escriba.local X-ME-Auth: dmljZW50ZS5ib3RldEB3YW5hZG9vLmZy X-ME-Date: Sat, 07 Mar 2015 17:26:28 +0100 X-ME-IP: 2.11.66.123 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.7; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 In-Reply-To: X-Original-Sender: vicente.botet@wanadoo.fr X-Original-Authentication-Results: mx.google.com; spf=none (google.com: vicente.botet@wanadoo.fr does not designate permitted sender hosts) smtp.mail=vicente.botet@wanadoo.fr 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:16844 Archived-At: This is a multi-part message in MIME format. --------------040008010001080806040309 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable Le 06/03/15 08:07, Tony V E a =C3=A9crit : > > > On Thu, Mar 5, 2015 at 11:44 PM, Tom Honermann=20 > > wrote: > > We have this for lambdas: > auto l =3D [](auto x) { return x; } > If we could do (something like) these for generic functions, I > would be thrilled: > auto <>f(auto x) { return x; } > auto <>f(Iterator i) { return i; } > > > The terse syntax with just 'auto' doesn't bother me (I think I will=20 > learn to scan for 'auto' params), but if we do choose to have=20 > distinctive syntax to note that it is a template, then I'll make a=20 > crazy suggestion: use the word 'template' > > template void f(auto x) { ... } > > Although 'auto' doesn't bother me, as others have mentioned, Concepts=20 > give no hints: > > void f(Number x) { ... } > > So either you know your concepts, or you IDE does (and gives them a=20 > different color or something) or maybe that is a reason to use 'template'= : > > template void f(Number x) { ... } > > (and thus use 'template' for the 'auto' case as well) > Could I suggest the use of something like '<>' to declare a type and the=20 required concept on the type parameter void f(Number<>N x) { ... } Number<>N x stands for a parameter x having type N satisfying Number. The Concept or the type can be omitted void f(<>N x) { ... } a parameter x having type N without any constraint. void f(Number<> x) { ... } a parameter x having an unknown type satisfying the Number concept. This void f(<> x) { ... } a parameter x having an unknown type without any constraint. I we consider that auto mean no constraint, the more verbose syntax=20 could have a sens also void f(auto<> x) { ... } I we consider that auto mean any type, the more verbose syntax could=20 have a sens also void f(<>auto x) { ... } In any case we have the token <> that recall that we are defining a=20 template. Vicente --=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/. --------------040008010001080806040309 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Le 06/03/15 08:07, Tony V E a =C3=A9crit= =C2=A0:


On Thu, Mar 5, 2015 at 11:44 PM, Tom Honermann <t= honermann@coverity.com> wrote:
We have this for lambdas:
=C2=A0 auto l =3D [](auto x) { return x; }
If we could do (something like) these for generic functions, I would be thrilled:
=C2=A0 auto <>f(auto x) { return x; }
=C2=A0 auto <>f(Iterator i) { return i; }

The terse syntax with just 'auto' doesn't bother me (I think I will learn to scan for 'auto' params), but if we do choose to have distinctive syntax to note that it is a template, then I'll make a crazy suggestion: use the word 'template'

=C2=A0=C2=A0=C2=A0 template void f(auto x) { ... }

Although 'auto' doesn't bother me, as others have mentioned, Concepts give no hints:

=C2=A0=C2=A0=C2=A0 void f(Number x) { ..= .. }

So either you know your concepts, or you IDE does (and gives them a different color or something) or maybe that is a reason to use 'template':

=C2=A0=C2=A0=C2=A0 template void f(Numbe= r x) { ... }

(and thus use 'template' for the 'auto' case as well)

Could I suggest the use of something like '<>' to declare a type and the required concept on the type parameter

=C2=A0=C2=A0=C2=A0 void f(Number<>N x) { ... }

Number<>N x

stands for

a parameter x having type N satisfying Number.

The Concept or the type can be omitted

=C2=A0=C2=A0=C2=A0 void f(<>N x) { ... }

a parameter x having type N without any constraint.

=C2=A0=C2=A0=C2=A0 void f(Number<> x) { ... }

a parameter x having an unknown type satisfying the Number concept.

This

=C2=A0=C2=A0=C2=A0 void f(<> x) { ... }

a parameter x having an unknown type without any constraint.

I we consider that auto mean no constraint, the more verbose syntax could have a sens also

=C2=A0=C2=A0=C2=A0 void f(auto<> x) { ... }

I we consider that auto mean any type, the more verbose syntax could have a sens also

=C2=A0=C2=A0=C2=A0 void f(<>auto x) { ... }

In any case we have the token <> that recall that we are defining a template.

Vicente





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