220 24878 <2bbe1861-b3b8-49cf-8405-ab840bd7b5fd@isocpp.org> article Path: news.gmane.org!not-for-mail From: NeoCode Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Go-like embedding Date: Wed, 2 Mar 2016 05:59:34 -0800 (PST) Lines: 227 Approved: news@gmane.org Message-ID: <2bbe1861-b3b8-49cf-8405-ab840bd7b5fd@isocpp.org> References: <245e65c5-c96d-4366-b616-814606d4ebe9@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_294_2059805163.1456927175054" X-Trace: ger.gmane.org 1456927188 8959 80.91.229.3 (2 Mar 2016 13:59:48 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 2 Mar 2016 13:59:48 +0000 (UTC) To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBD3J5LU7U4OBBSHD3O3AKGQEZPGELIA@isocpp.org Wed Mar 02 14:59:47 2016 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 1ab7JW-0005LT-Jq for gclcip-std-proposals@m.gmane.org; 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Wed, 02 Mar 2016 05:59:36 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.107.16.208 with SMTP id 77ls2147115ioq.71.gmail; Wed, 02 Mar 2016 05:59:35 -0800 (PST) X-Received: by 10.50.111.100 with SMTP id ih4mr947igb.3.1456927175816; Wed, 02 Mar 2016 05:59:35 -0800 (PST) In-Reply-To: <245e65c5-c96d-4366-b616-814606d4ebe9@isocpp.org> 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:24878 Archived-At: ------=_Part_294_2059805163.1456927175054 Content-Type: multipart/alternative; boundary="----=_Part_295_1770055624.1456927175054" ------=_Part_295_1770055624.1456927175054 Content-Type: text/plain; charset=UTF-8 On Wednesday, March 2, 2016 at 4:46:29 PM UTC+3, Nicol Bolas wrote: > > On Wednesday, March 2, 2016 at 8:27:30 AM UTC-5, NeoCode wrote: >> >> 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 >> >> >> > ... what's wrong with inheritance? I know people tend to believe that > using inheritance for something like this is wrong, but these cases are > *exactly* why C++ has robust support for multiple inheritance, unlike > most languages. > Nothing wrong with inheritance. It's just an additional opportunity. -- 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/2bbe1861-b3b8-49cf-8405-ab840bd7b5fd%40isocpp.org. ------=_Part_295_1770055624.1456927175054 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Wednesday, March 2, 2016 at 4:46:29 PM UTC+3, N= icol Bolas wrote:
On Wednesday, March 2, 2016 at 8:27:30 AM UTC-5, NeoCode wrote:
In Go programming language= ,=C2=A0there is a feature named "emedding",=C2=A0which is used in= stead of classic c++-like inheritance.
For example:

type SmallBox struct {
=C2=A0 =C2=A0 =C2=A0 =C2=A0 a, b, c int=
}
type BigBox struct= {
= =C2=A0 =C2=A0 =C2=A0 =C2=A0 Timestamp time.Time
=C2=A0 =C2=A0 =C2=A0 =C2=A0 SmallBox =C2=A0// <<< embedding
=C2=A0 =C2=A0 =C2=A0 =C2=A0 Name []= string
}

This is very simple and= low-level extension of the concept of inheritance;=C2=A0the programmer exp= licitly specifies the location of the base object in the successor.=C2=A0It= is strange that 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&qu= ot; keyword (or some other keyword, eg. "embed") to indicate the = embedded fields.

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

struct BigBox {
=C2=A0time_t Time= stamp; =
=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.inlinedBox.<= span style=3D"color:#000">b =3D 10; // u= sing an intermediate name, = <= span style=3D"color:#800">like aggregation
=


... what's wrong with inherit= ance? I know people tend to believe that using inheritance for something li= ke this is wrong, but these cases are exactly why C++ has robust sup= port for multiple inheritance, unlike most languages.

Nothing wrong with inheritance. It's just an= additional opportunity.=C2=A0

--
You received this message because you are subscribed to the Google Groups &= quot;ISO C++ Standard - Future Proposals" group.
To unsubscribe from this group and stop receiving emails from it, send an e= mail to std-proposa= ls+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/2bbe1861-b3b8-49cf-8405-ab840bd7b5fd= %40isocpp.org.
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