220 37129 article Path: news.gmane.org!.POSTED!not-for-mail From: Richard Hodges Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Use of "implement" when overriding a virtual method that does not have an implementation, yet. 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[209.85.220.41]) by mx.google.com with SMTPS id r84sor1915044itr.56.2018.02.28.14.33.06 for (Google Transport Security); Wed, 28 Feb 2018 14:33:06 -0800 (PST) Received-SPF: pass (google.com: domain of hodges.r@gmail.com designates 209.85.220.41 as permitted sender) client-ip=209.85.220.41; X-Received: by 10.36.127.10 with SMTP id r10mr122132itc.101.1519857186072; Wed, 28 Feb 2018 14:33:06 -0800 (PST) Original-Received: by 10.2.102.105 with HTTP; Wed, 28 Feb 2018 14:33:05 -0800 (PST) In-Reply-To: <8462ee66-9e9a-4579-8246-64861bf4a349@isocpp.org> X-Original-Sender: hodges.r@gmail.com X-Original-Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=YovX/4MZ; spf=pass (google.com: domain of hodges.r@gmail.com designates 209.85.220.41 as permitted sender) smtp.mailfrom=hodges.r@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:37129 Archived-At: --001a1147b726af6e7205664d53a2 Content-Type: text/plain; charset="UTF-8" On 28 February 2018 at 22:04, wrote: > Pretty often I find myself wanting to declare a method as *implement*, as > opposed to using *override*. > > Here an example: > > #include > > class A > { > public: > virtual ~A() {} > virtual void foo() { std::cout << "A::foo" << std::endl; } > virtual void bar() = 0; > }; > > class B : public A > { > public: > void foo() override { std::cout << "B::foo" << std::endl; } > void bar() implement { std::cout << "B::bar" << std::endl; } > }; > > It helps readability. The use of *override* implies that an implementation > already exists and is going to be overridden, which is not the case for > *A::bar*. > *implement* would just fit in this case. > > If in the future an implementation for *A::bar* is provided, the compiler > will let > the developer know that an implementation is now being overridden, that is > no > longer "implementing it", but "overriding it", which may be bad. I, as a > developer, > want to be aware of that scenario. I would be able to decide whether the > base > implementation needs to be executed inside the derived class' > implementation, > and *when* it must be executed. > > For retro-compatibility, *override* could always be used where the use of > *implement* is allowed. > > On the other hand, *implement* would become a reserved keyword of the C++ > programing language. > > > > Thoughts? > These are my thoughts: #define implement override But not in any code I'll end up maintaining, or any public header files please. > > -- > 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/8462ee66-9e9a-4579- > 8246-64861bf4a349%40isocpp.org > > . > -- 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/CALvx3hbSTNk-Tq3EH5KAOWS9NT-zee8n1urjgKj-V_tidz%2BKLw%40mail.gmail.com. --001a1147b726af6e7205664d53a2 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable


On 28 February 2018 at 22:04, <cristian64@gmail.com>= wrote:
Pretty often I f= ind myself wanting to declare a method as implement, as
opposed t= o using override.

Here an example:

#include <iostream>

cla= ss A
{
<= span style=3D"color:rgb(0,0,136)" class=3D"m_-1400620095787787110styled-by-= prettify">public:
=C2=A0 =C2=A0 virtual ~= A() {}
=C2=A0 =C2=A0 virtual void foo() { std::cout &l= t;< "A::foo"= << std::endl; }
=C2=A0 =C2=A0 virtual void bar() =3D 0;
};
=C2=A0
class B : public A
{
pub= lic:
=C2=A0 =C2=A0 void foo() override {= std::cout << "B::foo" << std:= :endl; }
=C2=A0 =C2=A0 void bar() implement <= /span>{ std::cout << &quo= t;B::bar" <<= std::endl;<= span style=3D"color:rgb(0,0,0)" class=3D"m_-1400620095787787110styled-by-pr= ettify"> }
};

It helps readability. The use of overr= ide implies that an implementation
already exists and is going to be= overridden, which is not the case for A::bar.
implement would just fit in this c= ase.

If in the future an implementation for A::bar is provided, the compiler will le= t
the developer know that an implementation is now being overridden, tha= t is no
longer "implementing it", but "overriding it"= ;, which may be bad. I, as a developer,
want to be aware of that scenari= o. I would be able to decide whether the base
implementation needs to be= executed inside the derived class' implementation,
and when = it must be executed.

For retro-compatibility, override could = always be used where the use of
implement is allowed.

On t= he other hand, implement would become a reserved keyword of the C++<= br>programing language.



= =C2=A0
Thoughts?
=

These are my thoughts:

#define implement ove= rride

But not in any code I'll end = up maintaining, or any public header files please.

=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-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/8462= ee66-9e9a-4579-8246-64861bf4a349%40isocpp.org.

--
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To view this discussion on the web visit h= ttps://groups.google.com/a/isocpp.org/d/msgid/std-proposals/CALvx3hbSTNk-Tq= 3EH5KAOWS9NT-zee8n1urjgKj-V_tidz%2BKLw%40mail.gmail.com.
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