220 10599 <67EC0741-C576-4E2B-AA57-04D7280DEEB5@gmail.com> article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: overloading on function template parameters that don't appear as function parameters Date: Sat, 10 May 2014 16:07:32 +0800 Lines: 81 Approved: news@gmane.org Message-ID: <67EC0741-C576-4E2B-AA57-04D7280DEEB5@gmail.com> References: <536CDAF5.4020407@wanadoo.fr> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 7.2 \(1874\)) Content-Type: multipart/alternative; boundary="Apple-Mail=_F54A9CD0-A87B-40BD-BA80-F2974602C7BB" X-Trace: ger.gmane.org 1399709268 18069 80.91.229.3 (10 May 2014 08:07:48 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 10 May 2014 08:07:48 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRBSV4W6NQKGQEUNTKUOA@isocpp.org Sat May 10 10:07:40 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-ve0-f197.google.com ([209.85.128.197]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Wj2Jo-0006Fp-9V for gclcip-std-proposals@m.gmane.org; Sat, 10 May 2014 10:07:40 +0200 Original-Received: by mail-ve0-f197.google.com with SMTP id db11sf16948924veb.0 for ; Sat, 10 May 2014 01:07:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:message-id:mime-version:subject:date :references:to:in-reply-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=qBYv77Q5YTN2OCBUBjhfErPqmeuLDBD5v2tBgagQzsU=; b=Kq+uouOfYOIUsVj4WkNpwvU+ty1mBb/cBrvCxWVO9ix9Ja3wUKPaMaViUqUHBLxgTN Edgm5u1fWVmY8B96EzkNMC91EiPIUNPL+W9UhFoWSErukQFaV/OGar0oNV/majQRwUFZ tbHH33ixuAeK9KnXHRz82s5zTeMS9dGqU4UMIK662p3yBwtxw6kq+BhE82RqALn53liC j+d9+kDjYU4+85ituiBHFhj+3cKNRyPX64WaeQJGhyS7/M5gOOgQjAW4gHImxan8YVJZ FpU3A74ZNXyJw/e0CemMgRNrYQAmgH7gj+I4MKRz0l8Gs7ryQPa5PZlxjHTlzsOybCW2 zA1w== X-Gm-Message-State: ALoCoQmBaVY3WdFR97dhxumcCoq5hstHsl27SDRZnJBT/yx4tG5x7QIV9whKyUaOMSRXRnO/NX3f X-Received: by 10.236.109.169 with SMTP id s29mr6648736yhg.43.1399709259482; Sat, 10 May 2014 01:07:39 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.11.4 with SMTP id m4ls818385igb.4.gmail; Sat, 10 May 2014 01:07:38 -0700 (PDT) X-Received: by 10.50.111.138 with SMTP id ii10mr18650796igb.34.1399709258420; Sat, 10 May 2014 01:07:38 -0700 (PDT) Original-Received: from mail-ie0-x231.google.com (mail-ie0-x231.google.com [2607:f8b0:4001:c03::231]) by mx.google.com with ESMTPS id qd1si2471728igb.20.2014.05.10.01.07.38 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 10 May 2014 01:07:38 -0700 (PDT) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:4001:c03::231 as permitted sender) client-ip=2607:f8b0:4001:c03::231; Original-Received: by mail-ie0-f177.google.com with SMTP id rp18so4751971iec.8 for ; Sat, 10 May 2014 01:07:38 -0700 (PDT) X-Received: by 10.50.112.202 with SMTP id is10mr18570389igb.7.1399709258260; Sat, 10 May 2014 01:07:38 -0700 (PDT) Original-Received: from [172.20.10.2] ([121.54.54.150]) by mx.google.com with ESMTPSA id u2sm5026696igs.10.2014.05.10.01.07.35 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Sat, 10 May 2014 01:07:37 -0700 (PDT) In-Reply-To: <536CDAF5.4020407@wanadoo.fr> X-Mailer: Apple Mail (2.1874) X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:4001:c03::231 as permitted sender) smtp.mail=potswa@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=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:10599 Archived-At: --Apple-Mail=_F54A9CD0-A87B-40BD-BA80-F2974602C7BB Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=ISO-8859-1 On 2014-05-09, at 9:41 PM, Vicente J. Botet Escriba wrote: > Is this the correct way to define this generic interface? I don't think it's generic at all. exception_ptr is a different animal from= exception, so make_error should not be able to produce both. > Do you see any failures I have not identified in the design? > Do you know of a better way to manage with this kind of factory functions= ? You seem to have reinvented tag dispatching. In general, a function templat= e with "partial specializations" will need some form of dispatching, either= by tags or SFINAE, and either at the interface overload set or behind a di= spatcher wrapper function as you did. None of this seems like a big deal to me. On one hand, you hit a case where= you want function template partial specialization. On the other hand, in t= his case it's a code smell that the interface is overextended. --=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/. --Apple-Mail=_F54A9CD0-A87B-40BD-BA80-F2974602C7BB Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1
On 2014&= ndash;05–09, at 9:41 PM, Vicente J. Botet Escriba <vicente.botet@wanadoo.fr> wrote:
<= br class=3D"Apple-interchange-newline">
Is this th= e correct way to define this generic interface?

I don’t think it’s generic at all. exception_ptr is a different animal from exception, so make_error sho= uld not be able to produce both.

Do you = see any failures I have not identified in the design?
Do you know of a b= etter way to manage with this kind of factory functions?

You seem to have reinvented tag dispatching. In general, = a function template with “partial specializations” will need so= me form of dispatching, either by tags or SFINAE, and either at the interfa= ce overload set or behind a dispatcher wrapper function as you did.

None of this seems like a big deal to me. On one hand, you hit= a case where you want function template partial specialization. On the oth= er hand, in this case it’s a code smell that the interface is overext= ended.

--

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