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Wed, 09 Mar 2016 12:45:58 -0800 (PST) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.43.162 with SMTP id x2ls15367igl.34.gmail; Wed, 09 Mar 2016 12:45:57 -0800 (PST) X-Received: by 10.50.43.234 with SMTP id z10mr12943igl.4.1457556356994; Wed, 09 Mar 2016 12:45:56 -0800 (PST) In-Reply-To: <0519dbd8-89d0-4e71-90af-e4131dffdea4@isocpp.org> X-Original-Sender: wkaras@yahoo.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: Original-Sender: std-proposals@isocpp.org List-Subscribe: , List-Unsubscribe: , X-Original-From: Walt Karas Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:25094 Archived-At: ------=_Part_6615_255236201.1457556355979 Content-Type: multipart/alternative; boundary="----=_Part_6616_175938585.1457556355980" ------=_Part_6616_175938585.1457556355980 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On Wednesday, March 9, 2016 at 3:05:16 PM UTC-5, Cleiton Santoia wrote: > > A hopefully illustrative concrete example: >> >> struct A { int i; }; >> struct B { int i; }; >> struct C : public A, public B { }; >> struct D { int i, j; }; >> > =20 > >> B C::*p1 =3D &C:::B; >> int D::*p2 =3D &D::j; >> >> p1 and p2 would be initialized with the same numeric value from a machin= e=20 >> language point of view. Typically 4 on a 32-bit architecture. >> > > > The type of p1 is "B member object of C"=20 > The type pf p2 is "int member object of D" > > p2, I understand, to use it, you must;=20 > > D d; // instantiate d > d.*p2 =3D 10; // same as D.j =3D 10; i can assign an int here > > p1 I don=C2=B4t, you must;=20 > > C c; // instantiate c > c.*p1 =3D B() // what can i assign here ? a instance of B ? > Yes that would work. This: c.*p1 =3D B(); (c.*.p1).i =3D 5; would make the same changes to c as: static_cast(c).i =3D 5; --=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/11911c74-3792-4cbf-858b-d8c7aeb8e753%40isocpp.or= g. ------=_Part_6616_175938585.1457556355980 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable


On Wednesday, March 9, 2016 at 3:05:16 PM UTC-5, C= leiton Santoia wrote:
A ho= pefully illustrative concrete example:

struct A { int i; };
struc= t B { int i; };
struct C : public A, public B { };
struct D { int i, = j; };
=C2=A0
B C::*p1 =3D &C:::B;
int D::*p= 2 =3D &D::j;

p1 and p2 would be initialized with the same numeri= c value from a machine language point of view.=C2=A0 Typically 4 on a 32-bi= t architecture.


<= div>The type of p1 is "B member object of C"=C2=A0
=
The type pf p2 is "int member object of D"
<= br>
p2, I understand, to use it, you must;=C2=A0

D d; // instantiate d
d.*p2 =3D 10; // same as D.j =3D 1= 0; i can assign an int here

p1 I don=C2=B4t, you m= ust;=C2=A0

C c; // instantiate c
c.*p1 = =3D B() =C2=A0// what can i assign here ? a instance of B ?

Yes that would work.=C2=A0 This:

c.*p1 =3D B();(c.*.p1).i =3D 5;

would make the same changes to c as:

stati= c_cast<B &)(c) =3D B();
static_cast<B &>(c).i =3D 5;

--
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