220 19863 <4671850d-b823-436d-b097-f514073cc92e@isocpp.org> article Path: news.gmane.org!not-for-mail From: Nicol Bolas Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: default arguments Date: Sat, 15 Aug 2015 10:29:29 -0700 (PDT) Lines: 89 Approved: news@gmane.org Message-ID: <4671850d-b823-436d-b097-f514073cc92e@isocpp.org> References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_2_1853422674.1439659769915" X-Trace: ger.gmane.org 1439659778 23991 80.91.229.3 (15 Aug 2015 17:29:38 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 15 Aug 2015 17:29:38 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBB6XNXWXAKGQEG52RKLQ@isocpp.org Sat Aug 15 19:29:33 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-pd0-f198.google.com ([209.85.192.198]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZQfGu-0005ec-S9 for gclcip-std-proposals@m.gmane.org; Sat, 15 Aug 2015 19:29:33 +0200 Original-Received: by pdbnh15 with SMTP id nh15sf171525302pdb.1 for ; Sat, 15 Aug 2015 10:29:31 -0700 (PDT) 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 :content-type: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=xfolpeBWcmdxoSoWjwghxtYEaBbo8VZjhIjKca0RYs4=; b=fM02B9E/m9q8yAChsJItwsQ2fZkS3feWe/ZSfKMybpZS4anHQe6mLmJHqKr83frm3w 2bx7TiIJhWqw+y4pg+B/wixvSXjn90lVQkEzaJsBustn/PergZoceY2vmpv37m9lwfyd CAZOBD5SackeLoztpIivWjCitE7CJxaXmmuYuWdfVtzBFm/OSomLx3vaLL4poycqAe8J C0qMqhzNE77Ws1CtErBqQtbWJ5dJOa8l+G4e5b+RG7ASo0zlUkMjmgOLiiFAHK1pSwlH EpCQkKT7LYDEs6a0eSrcEmksDxcHQl1PuOMffpzpPgkcJsWEjAlSUeRZa5siNbnR7/OR 3eBQ== 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:content-type: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=xfolpeBWcmdxoSoWjwghxtYEaBbo8VZjhIjKca0RYs4=; b=Ff7lz/qtTb4i+s9U1lySsaQSuB4Gakn+6FKnK67x7angcfMTDvGHI6+f63bpucJr9j 57XyZjuUUL1OXPZYgSSn73oGpvIUMYM/uf3ODTKTUa1I80Xq4sNJtqeGrpD4ki2LaEhc bK8aKpp0VnN0/EU252gzV8k0VcdprQt/0U9ApxMUDiQWyfJULdRGc/pxfoAagHMWuIdx zXXD6foAxWuC0/k2GgpuCWJiX2klJVLQ4IdXdwJUCEJSCx4G2YAUSqUQtsWiPCbv9haw 7L6B3VZUsOIYJEtdpsk6fHmStz52HRNfi4C9oyKj/Vx4qYrf9RByr4JDNV1rLLVAJBtp 92Fg== X-Gm-Message-State: ALoCoQkup7TCFRA2bwGqsY3CAQC0IbrnFmay+9nEoRRGmEn5TuDHXumXS2sIV7ZBdgm3QcAhviMe X-Received: by 10.68.180.161 with SMTP id dp1mr25546207pbc.13.1439659771728; Sat, 15 Aug 2015 10:29:31 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.109.2 with SMTP id k2ls1723510qgf.79.gmail; Sat, 15 Aug 2015 10:29:30 -0700 (PDT) X-Received: by 10.140.104.115 with SMTP id z106mr339806qge.23.1439659770585; Sat, 15 Aug 2015 10:29:30 -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:19863 Archived-At: ------=_Part_2_1853422674.1439659769915 Content-Type: multipart/alternative; boundary="----=_Part_3_267507032.1439659769915" ------=_Part_3_267507032.1439659769915 Content-Type: text/plain; charset=UTF-8 On Saturday, August 15, 2015 at 12:49:50 PM UTC-4, Arthur Tchaikovsky wrote: > > Hi, > Does anyone see helpfulness of such solution: > Having fnc: > > void f(int a = 0, int b = 1, int c = 2, int d = 3); > > I think that it would be nice to be able to say whilst calling it and > requiring only some of those args to be non-default: > > f(default,2,default,4); > > Thoughts? > This is probably the best language enhancement to default arguments I've seen (admittedly, that's not saying much, considering the quality of the others). It uses an existing keyword in a way that doesn't break existing code. It provides genuinely useful functionality, solving a (relatively minor) problem. And it would make it reasonable to define default arguments other than at the end of a parameter list. My only concern is that it could tie up more useful syntax. With Uniform Initialization syntax, you can perform value initialization and construction initialization. But there's no way to generically use default initialization. So we might someday want `f(default)` to mean "default initialize the parameter". Then again, maybe we don't want that. -- --- 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/. ------=_Part_3_267507032.1439659769915 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
On Saturday, August 15, 2015 at 12:49:50 PM UTC-4, Arthur = Tchaikovsky wrote:
Hi,
Does anyone see helpfulness of such solution:
Having fnc:
void f(int a =3D 0, int b =3D 1, int c =3D 2, int d =3D 3);

I = think that it would be nice to be able to say whilst calling it and requiri= ng only some of those args to be non-default:

f(default,2,default,4)= ;

Thoughts?

This is probably the best= language enhancement to default arguments I've seen (admittedly, that&= #39;s not saying much, considering the quality of the others). It uses an e= xisting keyword in a way that doesn't break existing code. It provides = genuinely useful functionality, solving a (relatively minor) problem. And i= t would make it reasonable to define default arguments other than at the en= d of a parameter list.

My only concern is that it could tie up more = useful syntax. With Uniform Initialization syntax, you can perform value in= itialization and construction initialization. But there's no way to gen= erically use default initialization. So we might someday want `f(default)` = to mean "default initialize the parameter".

Then again, ma= ybe we don't want that.

--

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