220 39851 article Path: news.gmane.org!.POSTED!not-for-mail From: Justin Bassett Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: What do we want from named paramaters Date: Thu, 16 Aug 2018 21:39:06 -0700 Lines: 121 Approved: news@gmane.org Message-ID: References: <1534441498.3721109.1476442920.71D445BF@webmail.messagingengine.com> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="0000000000007a12a905739a24f2" X-Trace: blaine.gmane.org 1534480634 27385 195.159.176.226 (17 Aug 2018 04:37:14 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 17 Aug 2018 04:37:14 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBC5PL3NYWEDBB5VC3HNQKGQECD2ZOWY@isocpp.org Fri Aug 17 06:37:10 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-oi0-f72.google.com ([209.85.218.72]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fqWVZ-0006x3-79 for gclcip-std-proposals@m.gmane.org; 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[209.85.220.41]) by mx.google.com with SMTPS id p188-v6sor577880oib.146.2018.08.16.21.39.18 for (Google Transport Security); Thu, 16 Aug 2018 21:39:18 -0700 (PDT) Received-SPF: pass (google.com: domain of jbassett271@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 2002:aca:e6cd:: with SMTP id d196-v6mr868608oih.94.1534480757688; Thu, 16 Aug 2018 21:39:17 -0700 (PDT) In-Reply-To: <1534441498.3721109.1476442920.71D445BF@webmail.messagingengine.com> X-Original-Sender: jbassett271@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=oUJnlUz2; spf=pass (google.com: domain of jbassett271@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=jbassett271@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=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:39851 Archived-At: --0000000000007a12a905739a24f2 Content-Type: text/plain; charset="UTF-8" On Thu, Aug 16, 2018 at 10:45 AM Henry Miller wrote: > > In the past couple months I've seen several proposals for names > parameters. Each with a list of pros and cons, and because there are cons > arguments against them. I think we need a discussion on what we want > assuming some strawman acceptable syntax, and some thought of how many > limitations in corner cases we are willing to accept. > > I can think of 4 uses for names parameters. (If you don't understand these > I have simple code examples) > 1 . a function with more than one parameter of the same type is called > with the parameters in the wrong order > * Some people want this to be a compilation error, some want the > compiler to correct the problem and continue > 2. a function wants to take the same type to mean different things in > different contexts > 3. it isn't obvious from the type alone what a parameter means > 4. A function has a bunch of defaulted arguments and you want to change > one of the latter ones without specifying all the others > > First question: is this complete? > Second, which problems are worth solving? > Third, for problems worth solving, which is the better solution, and how > strongly attached to it are you? > Some other use cases: 5. In tandem with reflection, names could be used for their names. A formatting library could use this in tandem with reflection: fmt::format("{sign} {value}", .sign = "$", .value = 1.34_usd); Language bindings to e.g. Python could use it to specify names for parameters (e.g. this could expose the parameter names to the language bindings: m.def([](int .a, int .b) { return a + b; }) ) 6. This is a variation on 4. There may not be a bunch of defaulted arguments, but rather a few expert settings which you want the users to be able to tweak on rare occasions. 7. bool arguments have meaning. It's pretty well known that something like file.open("path/to/file.txt", true) is bad, because the bool has no meaning. But file.open("path/to/file.txt", ..append = true) isn't so bad because the meaning is apparent. Enums currently fill this role. -- 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/CAPuuy5dz_N4nwnDrmds%3DROEpnUY2jQU4XGcLytxXscB%3DX36P1g%40mail.gmail.com. --0000000000007a12a905739a24f2 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
On Thu, Aug 16= , 2018 at 10:45 AM Henry Miller <= hank@millerfarm.com> wrote:
=
In the past couple months I've seen several proposals for names paramet= ers.=C2=A0 Each with a list of pros and cons, and because there are cons ar= guments against them.=C2=A0 I think we need a discussion on what we want as= suming some strawman acceptable syntax, and some thought of how many limita= tions in corner cases we are willing to accept.

I can think of 4 uses for names parameters. (If you don't understand th= ese I have simple code examples)
1 . a function with more than one parameter of the same type is called with= the parameters in the wrong order
=C2=A0 =C2=A0 =C2=A0 *=C2=A0 Some people want this to be a compilation erro= r, some want the compiler to correct the problem and continue
2. a function wants to take the same type to mean different things in diffe= rent contexts
3. it isn't obvious from the type alone what a parameter means
4. A function has a bunch of defaulted arguments and you want to change one= of the latter ones without specifying all the others

First question: is this complete?
Second, which problems are worth solving?
Third, for problems worth solving, which is the better solution, and how st= rongly attached to it are you?

Some oth= er use cases:

5. In tandem with reflection, names = could be used for their names. A formatting library could use this in tande= m with reflection: fmt::format("{s= ign} {value}", .sign =3D "$", .value =3D 1.34_usd); L= anguage bindings to e.g. Python could use it to specify names for parameter= s=C2=A0=C2=A0(e.g. this could expose the parameter names to the language bi= ndings: m.def([](int .a, int .b) { retu= rn a + b; }) )
6. This is a variation on 4. There may not = be a bunch of defaulted arguments, but rather a few expert settings which y= ou want the users to be able to tweak on rare occasions.
7. bool = arguments have meaning. It's pretty well known that something like file.open("path/to/file.txt", tru= e) is bad, because the bool has no meaning. But file.open("path/to/file.txt", .append =3D true) isn't so bad because the meaning is apparent. Enums currently fil= l this role.

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To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CAPuuy5dz_N4n= wnDrmds%3DROEpnUY2jQU4XGcLytxXscB%3DX36P1g%40mail.gmail.com.
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