220 19899 <2cd343b5-b450-47c3-8ab9-806819768843@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: Tue, 18 Aug 2015 10:23:31 -0700 (PDT) Lines: 110 Approved: news@gmane.org Message-ID: <2cd343b5-b450-47c3-8ab9-806819768843@isocpp.org> References: <7066b166-9472-4ad6-ac3c-2db527ed7818@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_468_643451628.1439918611531" X-Trace: ger.gmane.org 1439918626 17204 80.91.229.3 (18 Aug 2015 17:23:46 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 18 Aug 2015 17:23:46 +0000 (UTC) Cc: mwoehlke.floss@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBCEKFTV6ZUMBBFGUZWXAKGQEJJ2BL7A@isocpp.org Tue Aug 18 19:23:44 2015 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f71.google.com ([209.85.218.71]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZRkbs-0002TR-V4 for gclcip-std-proposals@m.gmane.org; Tue, 18 Aug 2015 19:23:41 +0200 Original-Received: by oiey141 with SMTP id y141sf288650336oie.1 for ; Tue, 18 Aug 2015 10:23:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:cc: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=p4WBSRlPS6YpyN+BvK7hGbe6j7rchMifrcHXv485Tmg=; b=Y/kv16rLaEUpu1eQ8aGkVG7Kb4Yp8NNq532kiBocPKh75+ANeoIoPX+u0suIpPrCXi dgNg9b9SNIGzQlz0b9ofx/P3jV75+YEGCAd+Jp4/gU9IlycvrvBNUeBT6m6uUDzIVY0p nrhscdE4xiO6z/Cukqyv5xCVkyGALYo5MfpH5movJR4oTA+FwFacdGplESulKi0sXosU znO/sO+SMQ/l7lc4F8YCwxPSRckuqqYGNVYhr1anX+sk8k47bkdZLESZPdaew3OVBOt9 zcO2CHuShuu7ERFoFDSzR4RTn6O4FDRYWkLRpW4xSSdvDpbPLJ1FZJrZvqgZvEIpzSLg Gu+g== 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:cc: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=p4WBSRlPS6YpyN+BvK7hGbe6j7rchMifrcHXv485Tmg=; b=kmKlt7g6r0d+RI1lVJ6dae8eiq/bL9Q2DOdB8dTOotLq1AYys5H4O86WoNF33P2gC2 0Eto8JpWQYAWctZ1UlSj8tYr80h5VzL3skVPPpww3GYrJ/bq0mHk4k4PbdbrX3VLEtkh QDB+091hrfhmFwRljPLi5BR8d7Gm2kFiO6DEiR7OY3tZTN8PjKuxxpA1kEatryRB7203 dsGp9PsS+fmVQPpnhDTtyjfsBxGf9WvfNzbkfBCE/bkc8gkuqcRkPnpHCai4s93wfv5O EtDfusnWDPvWb/AMV+x5CJCo3Q93XTPaEAI0nAgVdCxz0nlrbAjt69f7Nj9Xj0QTAbVG IZdg== X-Gm-Message-State: ALoCoQk99RzPuloMvGUiLOQBmmWawK/G0Jz1GiiP5M3cJE5UmXA66aUGovURjH/51Tia6p2wwmBZ X-Received: by 10.107.6.197 with SMTP id f66mr7035221ioi.15.1439918614832; Tue, 18 Aug 2015 10:23:34 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.140.92.70 with SMTP id a64ls3209987qge.94.gmail; Tue, 18 Aug 2015 10:23:32 -0700 (PDT) X-Received: by 10.140.82.85 with SMTP id g79mr101875qgd.35.1439918612125; Tue, 18 Aug 2015 10:23:32 -0700 (PDT) In-Reply-To: <7066b166-9472-4ad6-ac3c-2db527ed7818@isocpp.org> 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:19899 Archived-At: ------=_Part_468_643451628.1439918611531 Content-Type: multipart/alternative; boundary="----=_Part_469_1189165838.1439918611531" ------=_Part_469_1189165838.1439918611531 Content-Type: text/plain; charset=UTF-8 On Tuesday, August 18, 2015 at 12:37:55 PM UTC-4, Arthur Tchaikovsky wrote: > > I dear to disagree with the statement that the following example is self > documenting and easier to read: > auto c3ptr = new C{.timeout = 1}; > How is this^^^ easier to read? And how is this self documenting? Only on > surface it seems that it is, both, but when you really think about it it is > neither self documenting nor easy to read. Why? Because having only one > argument initialized in {}, that is .timeout, leaves us with question, is > that the only argument to that class, or are there any other? > If I'm looking to understand what `new C{.timeout=1};` means, I don't care how many arguments `C` could have in its constructor. From the user's perspective, that's simply irrelevant. What matters is what it means to pass the value `1` to the `timeout` argument of the constructor. And since the word `timeout` is there, I can at least take a pretty good guess as to what it means. Remember: the whole point of default arguments is that you *don't have* to know about them. To make a function that takes 6 arguments look like a function that takes 3. Seeing `default` for an argument is just pointless noise, which is necessary only because C++ doesn't allow for positional or named arguments. > If so, are those arguments inited by default? If so, how many? Etc. > Compared to this: > auto c3ptr = new C(default, 1); // use a shorter timeout > It is immediately obvious how many arguments there are and which one of > them are default. And as for self documentation? > auto c3ptr = new C(default, /*timeout*/1); // use a shorter timeout > Comments are not "self documentation". Comments are not checked; *syntax* is. -- --- 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_469_1189165838.1439918611531 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Tuesday, August 18, 2015 at 12:37:55 PM UTC-4, = Arthur Tchaikovsky wrote:
I dear to disagree with the statement that the following exampl= e is self documenting and easier to read:
auto c3ptr =3D new C{.timeout = =3D 1};
How is this^^^ easier to read? And how is this self documenting? Only o= n surface it seems that it is, both, but when you really think about it it = is neither self documenting nor easy to read. Why? Because having only one = argument initialized in {}, that is .timeout, leaves us with question, is t= hat the only argument to that class, or are there any other?

If I'm looking to understand what `new C{.timeout=3D1};` m= eans, I don't care how many arguments `C` could have in its constructor= .. From the user's perspective, that's simply irrelevant. What matte= rs is what it means to pass the value `1` to the `timeout` argument of the = constructor.

And since the word `timeout` is there, I can at least t= ake a pretty good guess as to what it means.

Remember: the whole poi= nt of default arguments is that you don't have to know about the= m. To make a function that takes 6 arguments look like a function that take= s 3. Seeing `default` for an argument is just pointless noise, which is nec= essary only because C++ doesn't allow for positional or named arguments= ..
=C2=A0
If so, are those arguments inited by default? If so, how many? Etc.Compared to this:
auto c3ptr =3D new C(default, 1); // use a shorter ti= meout
It is immediately obvious how many arguments there are and which one of= them are default. And as for self documentation?
auto c3ptr =3D new C(d= efault, /*timeout*/1); // use a shorter timeout

Comments are not "self documentation&q= uot;. Comments are not checked; syntax is.

--

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