220 38672 <60dffd75-ebc3-4e4c-8666-f304be8f6136@isocpp.org> article Path: news.gmane.org!.POSTED!not-for-mail From: m.cencora@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Three way comparison of arrays Date: Fri, 15 Jun 2018 11:45:33 -0700 (PDT) Lines: 143 Approved: news@gmane.org Message-ID: <60dffd75-ebc3-4e4c-8666-f304be8f6136@isocpp.org> References: <9c6a84e4-66a2-4a25-8372-c7a6c7b8de25@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_8599_1168304985.1529088333500" X-Trace: blaine.gmane.org 1529088209 19085 195.159.176.226 (15 Jun 2018 18:43:29 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 15 Jun 2018 18:43:29 +0000 (UTC) Cc: m.cencora@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBD7YFUMJRYMBBTUSSDMQKGQEPR4B44Y@isocpp.org Fri Jun 15 20:43:25 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yb0-f200.google.com ([209.85.213.200]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fTtgy-0004pK-Mj for gclcip-std-proposals@m.gmane.org; Fri, 15 Jun 2018 20:43:24 +0200 Original-Received: by mail-yb0-f200.google.com with SMTP id h29-v6sf7174554ybj.22 for ; Fri, 15 Jun 2018 11:45:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=Y1WZYJaAtAmr/dGUxbRJNsn2WPah9vu/kdRLyVIkAMk=; b=ACo4d/7Zx+DxZuLS2/0LrVHCKa0uVfi/BPBlFqnYAiijNWePMybyuiIQV+N1J3KrM4 oWbxjNySNuDwlO1D1nz6S1rTZm29J8txS0E/aMGxYmLjfKaXTRpnPNi347daG6bJqyVu 3xQLuoGJh9dO2rF+6SWpwC0zRyq6BduCRCR8hPhpFGWj/crEmiHc1xLVVi6qxxPJUNcn jnJEY75VqqNJVGZGKd+jaRy0GsxZLs5LLXOYH0zSg/cDJejm5xXYkz5Oq8n+I/BJsaTx q6wM74iKeZ4dFU94zjkTPShd8QAFSpPv4nfM7wx6O6y1UIRmJNcHCIxAYlYa9TB3fkLe pYgQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:message-id:in-reply-to:references:subject :mime-version:x-original-sender:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe; bh=Y1WZYJaAtAmr/dGUxbRJNsn2WPah9vu/kdRLyVIkAMk=; b=hK8TqfZCTHq3HiLN1CeB2cN0+fahjXdqN5D0rejNZ5sHr5nT6R5gR/1b05PDzVhZl3 GHBMoUZfeRCIazz08t6OFkX5NtHfvLUivGMZSUnwcmhTWYs4pfZRYlLBEmtgrNb4TXpZ EzD4mrn/6At5OwUvkQ7z5gtJbfhvFVdo4UtRJ0rJbq/gydeRCrB734jnAGZJbiL3uh0C tmJg+F7OoCNBE9XPHmuM6+x9++gjNj8VumsK4djzcpqavCfxLApysPeb4CUWOVw/U90O /aQwMrY2Qlbms+coUCW9RORHQAoUcZ0mgeH2hVmtcX/1kckZOOUir17GQ0uRjqnWxHi9 F8+A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:message-id:in-reply-to :references:subject:mime-version: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=Y1WZYJaAtAmr/dGUxbRJNsn2WPah9vu/kdRLyVIkAMk=; b=eIOe/kjH3NnjVppFgxHVH8ZMUXWhevw3zLfYEOzyxIT0yQnRXfzC+243I3oCQlryhP 1b149kiiTy1L/jTSAJS18Xa5bid1Y+u7F2Qq8irlocFowchkIdOTPhyJ+1zz79C1nZYr j8eTKUEalgm3DgGmuq/zR9L3DEECCK/UJnmROBeAgLWLVM4eTGy5n+Z16n2k3RN6RHQ7 OWNv09GW6g81AfyCRCrHKDbezxtukPT2QPLojdsizxziZXbjxZW+HEqZHeOcN6gmzOmm ACTuSFGJa9sujVjHbOmmbXxLmccGFy50spdNn3lotC3ePsKhJ9/nHjUtq5lTFHIxT4uV UmdA== X-Gm-Message-State: APt69E1lygTOJ3kj1erUMKHvhxZtpJqIK2hIhH7KYxQGCgHG++Y//dYE bgSPwvEX/O70siojnh2GjO2cBg== X-Google-Smtp-Source: ADUXVKLIF2Yo+CchmoC5Zu0kmqMyLjUdbm5MqLif9nbozkJmRJDnAiFPrvbiTYccsHlfoM1tIzXezQ== X-Received: by 2002:a25:d696:: with SMTP id n144-v6mr781134ybg.16.1529088335700; Fri, 15 Jun 2018 11:45:35 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a5b:4c6:: with SMTP id u6-v6ls665783ybp.19.gmail; Fri, 15 Jun 2018 11:45:34 -0700 (PDT) X-Received: by 2002:a25:4296:: with SMTP id p144-v6mr129291yba.3.1529088334176; Fri, 15 Jun 2018 11:45:34 -0700 (PDT) In-Reply-To: <9c6a84e4-66a2-4a25-8372-c7a6c7b8de25@isocpp.org> X-Original-Sender: m.cencora@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:38672 Archived-At: ------=_Part_8599_1168304985.1529088333500 Content-Type: multipart/alternative; boundary="----=_Part_8600_1995088722.1529088333500" ------=_Part_8600_1995088722.1529088333500 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable This is a weak argument. We sacrifice the consistency of the operator<=3D>= =20 (works for all types) for doubtful consistency of copy and compare (of a=20 single type). We should be fixing language corner cases so it does what=20 programmer intents. So I'd rather have operator<=3D> for arrays in all cases, and fix array=20 copying as well. Regards, Maciej =20 W dniu pi=C4=85tek, 15 czerwca 2018 19:45:12 UTC+2 u=C5=BCytkownik Barry Re= vzin=20 napisa=C5=82: > > > > On Friday, June 15, 2018 at 10:34:10 AM UTC-5, m.ce...@gmail.com wrote: >> >> Hi, >> >> can we finally write idiomatic comparison code for arrays with three way= =20 >> compare? >> >> bool foo() >> { >> int a1[4] =3D { 1, 2, 3, 4 }, a2[4] =3D { 1, 2, 3, 4 }; >> return (a1 <=3D> a2) =3D=3D 0; >> } >> >> >> > No. This is explicitly rejected by design. Quoting from =20 > http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0515r3.pdf: > > For arrays, we don=E2=80=99t provide comparison if the array is not copya= ble in=20 >> the language, to keep copying and comparison consistent. Note that for t= wo=20 >> arrays, arr1<=3D>arr2 is ill-formed because the array-to-pointer convers= ion=20 >> is not applied >> > > Additionally, in Rapperswil, the two-way comparisons between arrays (i.e.= =20 > a1 =3D=3D a2) were deprecated. So now at least they both consistently wil= l not=20 > work.=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. To view this discussion on the web visit https://groups.google.com/a/isocpp= ..org/d/msgid/std-proposals/60dffd75-ebc3-4e4c-8666-f304be8f6136%40isocpp.or= g. ------=_Part_8600_1995088722.1529088333500 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
This is a weak argument. We sacrifice the consistency= of the operator<=3D> (works for all types) for doubtful consistency = of copy and compare (of a single type). We should be fixing language corner= cases so it does what programmer intents.
So I'd rather have= operator<=3D> for arrays in all cases, and fix array copying as well= ..

Regards,
Maciej
=C2=A0W dniu pi=C4=85tek, 15 czerwca 2018 19:45:12 UTC+2 u=C5=BCytkownik Barry R= evzin napisa=C5=82:


On Friday, June 15, 2018 at 10:34:10 AM UTC-5, m.ce...@gma= il.com wrote:
H= i,

can we finally write idiomatic comparison code for ar= rays with three way compare?

bool=C2=A0<= font color=3D"#000000">foo()
{<= /div>
=C2= =A0 =C2=A0 int a1[4] =3D { 1, 2,= 3, 4 }, a2[4] =3D { 1, 2, 3, 4 };
=C2=A0 = =C2=A0 return (a1 <=3D> a2) =3D=3D 0;
}



No. This is explicitly rejected b= y design. Quoting from=C2=A0=C2=A0http://www.open-std.org/jtc1/sc22/wg21/docs/pap= ers/2017/p0515r3.pdf:

For arrays, we don=E2=80=99t provide comparison i= f the array is not copyable in the language, to keep copying and comparison consistent. Note that for two arrays, arr1<=3D>arr2 is= ill-formed because the array-to-pointer conversion is not applied

Additionally,= in Rapperswil, the two-way comparisons between arrays (i.e. a1 =3D=3D a2) = were deprecated. So now at least they both consistently will not work.=C2= =A0

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