220 24874 article Path: news.gmane.org!not-for-mail From: NeoCode Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Go-like embedding Date: Wed, 2 Mar 2016 05:27:30 -0800 (PST) Lines: 255 Approved: news@gmane.org Message-ID: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_449_579399996.1456925250415" X-Trace: ger.gmane.org 1456925255 8152 80.91.229.3 (2 Mar 2016 13:27:35 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 2 Mar 2016 13:27:35 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBD3J5LU7U4OBBQ6U3O3AKGQENN5P7CY@isocpp.org Wed Mar 02 14:27:34 2016 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-vk0-f69.google.com ([209.85.213.69]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ab6oP-0001G1-N4 for gclcip-std-proposals@m.gmane.org; Wed, 02 Mar 2016 14:27:34 +0100 Original-Received: by mail-vk0-f69.google.com with SMTP id e6sf334803302vkh.0 for ; Wed, 02 Mar 2016 05:27:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=isocpp-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:message-id: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=3sFOc7k52abC6UpRHzuKiUKDS3dCoGdv3piuyQmt/Yo=; b=s6A8bS3Ym8yXhoLGkBzG9dHVL48jGxOgECDQrtFOXuSvqkDzUpHMDMZPX/yZW6d0GJ wY+R6Z2tDND7w4rUbaWe1pEPLVswJlq3U89geMTi/1I/+pisJMLQryX/d3yn2+Jd49z9 8M2YfQcwtAWLFAp0ZBrXWvGq3lxCDgGSyE7MGIP5XuhK6ibtPcqXy5YtV4YQAcUFTzlN XgueUOpaThZsZcUzaBehoiMOZGQifZYFKxzm/KMDpYfq38Gx3vX4xdOFYkFl8thFSgb1 v0BNUVSI4aI02WRlKo6QcmoDCrcwWd4iJ3LcU9xGlAyHqFEeFRLequiB+3Kt0hiHOt58 Fq/A== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=date:from:to:message-id: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=3sFOc7k52abC6UpRHzuKiUKDS3dCoGdv3piuyQmt/Yo=; b=xN6yErd8cv/fNMOnZMjZ+Ofb4lsBiw52zL7o0uog+TpMCqDhuyjpCSlebo4xTD5w62 qL5pp5YUBg02PkaFDGHDTztY38jFbKo1U5XRdt5CBhjse6Ogqb8wyICrPEZq0AXxYcUB tnRAp/gLU6k/y5+kz/AlRG/3/R4Oujtld7SO6OmRrsnoFlIY+S8f3s+xZmdQLb28K4Xe f3DHn9GIFCl823OdeGwy6gZ7C1xrgpXcquhX28jsRTXFQM+cybrgC9r25csUcPCAk2H4 wLmuK6wZtMdN0bOXKM0hTZ2zW0B2GiPnmOpA/OWDXr1Kzdk6A17zvmDmlAG7oN+AxTWa 0u+A== 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: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=3sFOc7k52abC6UpRHzuKiUKDS3dCoGdv3piuyQmt/Yo=; b=hmnDJ++xYA7TqVPrWAV0c1tf/AO7VrPan/AItqp0Tz66ry35zMYRzX2DPOKLsI4t+s 1gWPTuhLc8hNEC2LGAEI20CXFxjt/aFhdQZSUil+6xi8xaBuLDAYg7OH+Dsr1l9tVhuN usqWQ7sp4MYFrzPE6sFSmwmdu3lanUEDtRCWs0s6hIgZxBWgvwludeml8DBMNI0IQeFT m1/Y6bT33BqNDeceMl/9h+5f6nOPgrIaPJKj8+WQyRlc/iEcFaV1BcJOeygimVgpXOKt G+8CL3JMmx7el5B54/wLQFDymTW1X1aBHvjtWlrn1j0dV0qHzmhDnTfVhDSclToQEm6H G3QQ== X-Gm-Message-State: AD7BkJJV3BQIQ9fFf3Ji+PcLmx4JJixHR5uZ5zNHZ3qkY3HxA2Oa8Prr0eQLugAN3ugMcw== X-Received: by 10.31.151.21 with SMTP id z21mr21117378vkd.7.1456925252758; Wed, 02 Mar 2016 05:27:32 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.165.193 with SMTP id o184ls2036975ioe.1.gmail; Wed, 02 Mar 2016 05:27:31 -0800 (PST) X-Received: by 10.50.183.36 with SMTP id ej4mr120948igc.1.1456925251367; Wed, 02 Mar 2016 05:27:31 -0800 (PST) X-Original-Sender: NeoProgramming@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:24874 Archived-At: ------=_Part_449_579399996.1456925250415 Content-Type: multipart/alternative; boundary="----=_Part_450_1470392765.1456925250415" ------=_Part_450_1470392765.1456925250415 Content-Type: text/plain; charset=UTF-8 In Go programming language, there is a feature named "emedding", which is used instead of classic c++-like inheritance. For example: type SmallBox struct { a, b, c int } type BigBox struct { Timestamp time.Time SmallBox // <<< embedding Name []string } This is very simple and low-level extension of the concept of inheritance; the programmer explicitly specifies the location of the base object in the successor. It is strange that this simple and obvious opportunity not appeared in the C language. I propose enhanced (compared with Go) feature of such embedding. We can use the existing "inline" keyword (or some other keyword, eg. "embed") to indicate the embedded fields. struct SmallBox { int a, b, c; }; struct BigBox { time_t Timestamp; inline SmallBox inlinedBox; std::string Name; }; As a result, we can access to the fields of SmallBox both directly and through an intermediate name "inlinedBox": BigBox box; box.a = 10; //directly, like inheritance box.inlinedBox.b = 10; // using an intermediate name, like aggregation -- 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/e85c46fd-5e5c-4e43-86ae-978da17cda0c%40isocpp.org. ------=_Part_450_1470392765.1456925250415 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
In Go programming language,=C2=A0there is a feature named = "emedding",=C2=A0which is used instead of classic c++-like inheri= tance.
For example:

type S= mallBox struct {<= br>=C2=A0 =C2=A0 =C2=A0 =C2=A0 a= , b, c int
}
type<= /span> BigBox struct<= /span> {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 = Timestamp<= span style=3D"color: #000;" class=3D"styled-by-prettify"> time.Time
=C2=A0 =C2=A0 =C2=A0 =C2=A0 SmallBox =C2=A0// <<< embedding<= /span>
=C2=A0 = =C2=A0 =C2=A0 =C2=A0 Name []string
}

This is very simple and low-level ext= ension of the concept of inheritance;=C2=A0the programmer explicitly specif= ies the location of the base object in the successor.=C2=A0It is strange th= at this simple and obvious opportunity not appeared in the C language.

I propose enhanced (compared with Go) feature of= such embedding.=C2=A0We can use the existing "inline" keyword (o= r some other keyword, eg. "embed") to indicate the embedded field= s.

struct Small= Box {
=C2=A0 int a, b, c;
};

struct BigBox {
=C2=A0time_t Timestamp;
=C2=A0inline SmallBox inlinedBox;
=C2= =A0std::string Name;
};

As a result, = we can access to the fields of=C2=A0SmallBox=C2=A0both directly and through= an intermediate name "inlinedBox":

=
BigBox box;
box.a =3D 10; //directly, like inheritance
box.i= nlinedBox.= b <= span style=3D"color: #660;" class=3D"styled-by-prettify">=3D 10; // using an intermediate name, like aggregation=


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