220 39715 article Path: news.gmane.org!.POSTED!not-for-mail From: rmbeer2@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: new feature: declare data that replaces the previous one, or similar situation.... Date: Sat, 11 Aug 2018 12:17:12 -0700 (PDT) Lines: 842 Approved: news@gmane.org Message-ID: References: Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_Part_1145_861094225.1534015032839" X-Trace: blaine.gmane.org 1534014909 29122 195.159.176.226 (11 Aug 2018 19:15:09 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 11 Aug 2018 19:15:09 +0000 (UTC) Cc: rmbeer2@gmail.com To: ISO C++ Standard - Future Proposals Original-X-From: std-proposals+bncBDI6L6W3SYLBBOPMXTNQKGQE6TS3EEA@isocpp.org Sat Aug 11 21:15:05 2018 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yw1-f71.google.com ([209.85.161.71]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1foZLs-0007UD-N5 for gclcip-std-proposals@m.gmane.org; Sat, 11 Aug 2018 21:15:05 +0200 Original-Received: by mail-yw1-f71.google.com with SMTP id c67-v6sf17460898ywc.21 for ; Sat, 11 Aug 2018 12:17:15 -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=JG7FuazQVDq5iMKyrW7WO0+9T3AjDrDEbq+0iptMvu8=; b=kMHNGiRrHWY4pKUI2tFe7maZRh52yTn6/nvNeaoG/umflizufGAPur8h+v5oMuneby hHnYgmgIh5ZuCst2W/8KbfpOjNc8pWTNpIhq+aXH3LQg4mOGoQt83XmJPVtJvHOMBEc7 bJDVi2R9xDCPjfwoiBu8qazCd7JZVMORV0VMT53jew7dycEJQnYvSFFqQUdZD0zSBgHs 3CQeJeNlVh9YAeOvv1d7C0yPtf7sE3ITGUiJ0fexTOkZgwMkqh7eU5D7KiD/+6kCLVYY 4OmzraUEFQLVkw66NXojFEb0YniJ0CxHboQ5E7kHnvqCl4w3ARb+sYKoUQYhhTKzgGiX jM8A== 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=JG7FuazQVDq5iMKyrW7WO0+9T3AjDrDEbq+0iptMvu8=; b=prDVGdBqeU0pCfyyOYg8JjOHSdyUH34azGHeIepM/3hdZ4s2oQhOYwUdpyVgNQbsdG GijbRPcfL/1/YtkdLNH32Z2Q5ZU4X7BRNlyCavuUgiLLuqFGeVvA6uzDEb/KJIfZM8xE zUy7YXjvWB+MZz+MI1goatRRjjrRjbTOUGodpCqd6zWDvIlEZmnrM/xGHf57BmUsOe24 bmmDoAhwzOqAjFYgHC0nGXweG3iqlwgQ/SbqagpXphdx/f7r+ZmTKOa+t0kNEzPI8vsg PflTx38Z3gTsZftOQO/2QhAeAmf7zyrxDfZH5NAOpWlJymFwUuJjxr8jdHup11ODyKrf +Jeg== 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=JG7FuazQVDq5iMKyrW7WO0+9T3AjDrDEbq+0iptMvu8=; b=kGLi+IkxdUSYPoWiETexY5cdANfcM0N8SOYnC2XLzOex17cJPEl+5Y9vD3HAk8Q/YD tgA2UUbir70B/6AhgT/On6rYmPP/ps08tZSwmcnca9v2TS3mbOSMdOknPi41kT73Pjwj H67qBTd3ZUOjtALIJPxoTu0soNwFheu+2k2KaNqi+f8Fb+lonqFGRSO9NJxS3DXM1i1R y9DAVeq+Dm9giTdpsSqxJJexq/1n6PPjqPGg+6uwnUXzlZeGCpzSnB2TJ/X9J4MlgiR6 owqS+lXYDnSPU/HwE5j2+nAG92Yx6NtWBmAkiIRlqssl/qIxhfTuPO2UxYfgaTXX0Z0a nXcQ== X-Gm-Message-State: AOUpUlH9q2L09BgXVc1s105QfjNID/rU5ocoPJzAto1eIInU8XhZm7KW Tf80ry6vqo1KnctR6he61/3Tnw== X-Google-Smtp-Source: AA+uWPwsIJtn+UKhsImyVe3r7uMMan2PW1rWuBV7wt+V8W5E92pZnlDS5n2UPvURz39ZTyXFxx5Bhw== X-Received: by 2002:a81:e60a:: with SMTP id u10-v6mr3650884ywl.70.1534015034942; Sat, 11 Aug 2018 12:17:14 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 2002:a81:8386:: with SMTP id t128-v6ls1979018ywf.17.gmail; Sat, 11 Aug 2018 12:17:13 -0700 (PDT) X-Received: by 2002:a0d:de01:: with SMTP id h1-v6mr246597ywe.3.1534015033454; Sat, 11 Aug 2018 12:17:13 -0700 (PDT) In-Reply-To: X-Original-Sender: rmbeer2@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:39715 Archived-At: ------=_Part_1145_861094225.1534015032839 Content-Type: multipart/alternative; boundary="----=_Part_1146_100014087.1534015032840" ------=_Part_1146_100014087.1534015032840 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Es por eso que estoy publicando en este grupo, C++ no permite este tipo de= =20 trabajo con 4 clases y con las siguientes respuestas de salidas. Este es el codigo original con la que cuento, es la definitiva, combina C++= =20 con C para compensar la carencia de C++. Si C++ no consigue resolver este= =20 problema agregando alguna nueva caracteristica no me queda otra que=20 utilizar C con C++ y utilizando lineas de C para trabajar con memoria: =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D #include class A { public: A(int z_) : z(z_) { } virtual void f1(){printf("-> A (z): %d\n",z);} int z; }; class C: public A { public: C(int y_) : y(y_), A(y_) { } virtual void f1(){printf("-> C (z): %d\n",z);A::f1();} long y; }; class B { public: B() { } virtual int init(){ ptra=3Dnew A(1); if(!ptra)return -1;return 0; } virtual void f2() { A&a=3D*((A*)ptra); printf("B (a.z): %d\n",a.z); a.f1(); } void*ptra; }; class D: public B { public: D() { } virtual int init(){ ptra=3Dnew C(3); if(!ptra)return -1;return 0; } virtual void f2() { C&a=3D*((C*)ptra); printf("D (a.z): %d\n",a.z); a.f1(); B::f2(); } }; int main(){ D d;B b; if(d.init())return -1; if(b.init())return -1; =20 b.f2(); printf("=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\n"); d.f2(); return 0; } /* RESPUESTA: B (a.z): 1 -> A (z): 1 =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D D (a.z): 3 -> C (z): 3 -> A (z): 3 B (a.z): 3 -> C (z): 3 -> A (z): 3 */ =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Hasta ahora no he obtenido ningun resultado sastisfactorio. El lunes, 11 de junio de 2018, 21:17:54 (UTC-3), rmb...@gmail.com escribi= =C3=B3: > > We have 2 classes that contain different data sets, one needs to use the= =20 > functions and variables of another class, so it is included as a member= =20 > pointing to the other class: > > member > A -------> B > > Code: > --------------------------------------- > > class A { > public: > A(int z_) : z(z_) { } > int z; > }; > > class B { > public: > B() : a(1) { } > void f2() { > std::cout << "A:" << a.z << std::endl; > } > A a; > }; > > --------------------------------------- > > Then you need to create an inheritance for each class, since you need to= =20 > cover a new interface layer. Let's call C and D, where C uses the base=20 > class A and D uses the base class B. > > member > A ---------> B > | | > |inheritance | inheritance > | | > v member v > C ---------> D > > Code: > --------------------------------------- > > class A { > public: > A(int z_) : z(z_) { } > int z; > }; > class C: public A { > public: > C(int y_) : y(y_), A(y_) { } > long y; > }; > > class B { > public: > B() : a(1) { } > void f2() { > std::cout << "A:" << a.z << std::endl; > } > A a; > }; > class D: public B { > public: > B() : a(3) { } > void f2() { > std::cout << "A:" << a.z << std::endl; > } > C a; > }; > > --------------------------------------- > > Here where the problems appear, if you create B you can access the data o= f=20 > A with the functions of B. But if you create D, you access the data of C+= A=20 > with the functions of D and C, but as soon as you call the functions=20 > inherited from B, B can only access the data of A that are totally in=20 > disuse, that is, create an instance in D generates in memory a variable "= a"=20 > with C+A, and also a variable "a" with A , being in class D a C+A, A, whe= re=20 > the last A is not used, only C+A, in A it ends up using when the function= s=20 > of B. are called. > It is only possible to create a new virtual type function as the only= =20 > case to access only C+A, but this generates junk code and in memory it=20 > reserves A as garbage: > > Code: > --------------------------------------- > #include > > class A { > public: > A(int z_) : z(z_) { } > int z; > }; > > class C: public A { > public: > C(int z_) : A(z_) { } > }; > > class B { > public: > B() : a(1) { } > void f2() { > std::cout << "A:" << get_C_a().z << std::endl; > } > virtual A const& get_C_a() { return a; } > A a; // Use only from B > }; > > class D : public B { > public: > D() : a(3) { } > void f2(){ > std::cout << "C+A:" << a.z << std::endl; > B::f2(); > } > C a; // Use C+A only from D > A const& get_C_a() override { return a; } > }; > > int main() { > B b; D d; > b.f2(); d.f2(); > return 0; > } > > /* OUTPUT: > A:1 > C+A:3 > A:3 > */ > > --------------------------------------- > > This would be the best option, but not the ideal one. Ideally, "C a;" of = D=20 > replace "A a;" of B, in this way D only uses C+A from "C a;" and B only= =20 > uses A from "A a;" > > This is my proposal, a keyword like 'virtual' (or can be any other) in th= e=20 > variable of the same name that is replaced by the variable definition of= =20 > the base class. > > Por ejemplo: > Code: > --------------------------------------- > #include > > class A { > public: > A(int z_) : z(z_) { } > int z; > }; > > class C: public A { > public: > C(int z_) : A(z_) { } > }; > > class B { > public: > B() : a(1) { } > void f2() { > std::cout << "A:" << a.z << std::endl; > } > virtual A a; // Use A only from B > }; > > class D : public B { > public: > D() : a(3) { } > void f2(){ > std::cout << "C+A:" << a.z << std::endl; > B::f2(); > } > virtual C a; // Use C+A only from D > }; > > int main() { > B b; D d; > b.f2(); d.f2(); > return 0; > } > > /* OUTPUT: > A:1 > C+A:3 > A:3 > */ > > --------------------------------------- > > well this might not be possible, since compiled the code, the binary code= =20 > uses the data from an expected position in the variables within the=20 > classes, so removing it from the list could alter the size and position o= f=20 > the variables. On the other hand it would be possible, since reserving=20 > memory from A or from C as C+A, generates a group of variables reserved i= n=20 > memories for each class even if it is C+A and calls functions of A which= =20 > omits C of C+A Just to have A in view, this could be an advantage. > I suggest some other option to simulate a replacement of variable A by C. > If there is a better method that fulfills the same purpose without=20 > breaking with the basic structure proposed here then much better. > > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D > > Tenemos 2 clases que contienen distintos conjuntos de datos, uno necesita= =20 > usar las funciones y variables de otra clase, por lo que se incluye como= =20 > miembro apuntando a la otra clase: > > member > A -------> B > > Code: > --------------------------------------- > > class A { > public: > A(int z_) : z(z_) { } > int z; > }; > > class B { > public: > B() : a(1) { } > void f2() { > std::cout << "A:" << a.z << std::endl; > } > A a; > }; > > --------------------------------------- > > Luego se necesita crear una herencia para cada clase, ya que necesita=20 > cubrir una nueva capa de interfaz. Llamemos C y D, donde C usa la clase= =20 > base A y D usa la clase base B. > > member > A ---------> B > | | > |inheritance | inheritance > | | > v member v > C ---------> D > > Code: > --------------------------------------- > > class A { > public: > A(int z_) : z(z_) { } > int z; > }; > class C: public A { > public: > C(int y_) : y(y_), A(y_) { } > long y; > }; > > class B { > public: > B() : a(1) { } > void f2() { > std::cout << "A:" << a.z << std::endl; > } > A a; > }; > class D: public B { > public: > B() : a(3) { } > void f2() { > std::cout << "A:" << a.z << std::endl; > } > C a; > }; > > --------------------------------------- > > Aqui donde aparecen los problemas, si creas B puedes acceder a los dato= s=20 > de A con las funciones de B. Pero si creas D, accedes a los datos de C+A= =20 > con las funciones de D y C, pero tan pronto llamas a las funciones=20 > heredadas de B, B solo puede acceder a los datos de A que estan totalment= e=20 > en desuso, es decir, crear una instancia en D genera en la memoria una=20 > variable "a" con C+A, y tambien una variable "a" con A, siendo en la clas= e=20 > D un C+A,A , donde la ultima A no se usa, solo C+A , en A se termina usan= do=20 > cuando se llama a las funciones de B. > Solo es posible crear una nueva funcion tipo virtual como unico caso= =20 > para acceder solamente a C+A, pero esto genera codigo basura y en la=20 > memoria se reserva A como basura: > > Code: > --------------------------------------- > #include > > class A { > public: > A(int z_) : z(z_) { } > int z; > }; > > class C: public A { > public: > C(int z_) : A(z_) { } > }; > > class B { > public: > B() : a(1) { } > void f2() { > std::cout << "A:" << get_C_a().z << std::endl; > } > virtual A const& get_C_a() { return a; } > A a; // Use only from B > }; > > class D : public B { > public: > D() : a(3) { } > void f2(){ > std::cout << "C+A:" << a.z << std::endl; > B::f2(); > } > C a; // Use C+A only from D > A const& get_C_a() override { return a; } > }; > > int main() { > B b; D d; > b.f2(); d.f2(); > return 0; > } > > /* OUTPUT: > A:1 > C+A:3 > A:3 > */ > > --------------------------------------- > > Esta seria la mejor opcion, pero no la ideal. Lo ideal es que "C a;" de D= =20 > remplace a "A a;" de B, de esta forma D solo usa C+A de "C a;" y B solo u= sa=20 > A de "A a;" > > Esta es mi propuesta, una palabra clave como 'virtual' (o puede ser=20 > cualquier otra) en la variable del mismo nombre que se remplace a la=20 > definicion de variable de la clase base. > > Por ejemplo: > Code: > --------------------------------------- > #include > > class A { > public: > A(int z_) : z(z_) { } > int z; > }; > > class C: public A { > public: > C(int z_) : A(z_) { } > }; > > class B { > public: > B() : a(1) { } > void f2() { > std::cout << "A:" << a.z << std::endl; > } > virtual A a; // Use A only from B > }; > > class D : public B { > public: > D() : a(3) { } > void f2(){ > std::cout << "C+A:" << a.z << std::endl; > B::f2(); > } > virtual C a; // Use C+A only from D > }; > > int main() { > B b; D d; > b.f2(); d.f2(); > return 0; > } > > /* OUTPUT: > A:1 > C+A:3 > A:3 > */ > > --------------------------------------- > > bien esto podria no ser posible, ya que compilado el codigo, el codigo=20 > binario utiliza los datos desde una posicion esperada en las variables=20 > dentro de las clases, por lo que eliminarlo de la lista podria alterar el= =20 > tama=C3=B1o y la posicion de las variables. Por otro lado seria posible, = ya que=20 > reservar memoria desde A o desde C como C+A, se genera un grupo de=20 > variables reservadas en memorias para cada clase incluso si es C+A y llam= ar=20 > a funciones de A lo cual omite C de C+A solo para tener a la vista A,=20 > podria ser esto una ventaja. > Sugiero alguna otra opcion para simular un remplazo de la variable A por = C. > Si existe algun metodo mejor que cumpla con el mismo proposito sin romper= =20 > con la estructura basica propuesta aqui entonces mucho mejor. > > --=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/ef755674-802e-4354-a98d-a782ee90cce2%40isocpp.or= g. ------=_Part_1146_100014087.1534015032840 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Es por eso que estoy publicando en este grupo, C++ no= permite este tipo de trabajo con 4 clases y con las siguientes respuestas = de salidas.
Este es el codigo original con la que cuento, es la d= efinitiva, combina C++ con C para compensar la carencia de C++. Si C++ no c= onsigue resolver este problema agregando alguna nueva caracteristica no me = queda otra que utilizar C con C++ y utilizando lineas de C para trabajar co= n memoria:

=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D
#include <stdio.h>

class A {
public:
  A(int z_) : z(z_) {    }
  virtual void f1(){printf("-> A (z): %d\n",z);}
  int z;
};
class C: public A {
public:
  C(int y_) : y(y_), A(y_) {    }
  virtual void f1(){printf("-> C (z): %d\n",z);A::f1();}
  long y;
};

class B {
public:
  B() { }
  virtual int init(){
    ptra=3Dnew A(1);
    if(!ptra)return -1;return 0;
  }
  virtual void f2() {
    A&a=3D*((A*)ptra);
    printf("B (a.z): %d\n",a.z);
    a.f1();
  }
  void*ptra;
};
class D: public B {
public:
  D() { }
  virtual int init(){
    ptra=3Dnew C(3);
    if(!ptra)return -1;return 0;
  }
  virtual void f2() {
    C&a=3D*((C*)ptra);
    printf("D (a.z): %d\n",a.z);
    a.f1();
    B::f2();
  }
};

int main(){
  D d;B b;

  if(d.init())return -1;
  if(b.init())return -1;
 =20
  b.f2();
  printf("=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D\n");
  d.f2();
  return 0;
}

/* RESPUESTA:
B (a.z): 1
-> A (z): 1
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
D (a.z): 3
-> C (z): 3
-> A (z): 3
B (a.z): 3
-> C (z): 3
-> A (z): 3
*/
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

Hasta ahora no he obtenido ningun resultado sastisfact= orio.

El lunes, 11 de junio de 2018, 21:17:54 (UTC-3), rmb...@= gmail.com escribi=C3=B3:
We have 2 classes that contain different data sets, one needs to= use the functions and variables of another class, so it is included as a m= ember pointing to the other class:

=C2=A0=C2=A0 member
A -------&= gt; B

Code:
---------------------------------------

c= lass A {
public:
=C2=A0=C2=A0 =C2=A0A(int z_) : z(z_) {=C2=A0=C2=A0 = =C2=A0}
=C2=A0=C2=A0 =C2=A0int z;
};

class B {
public:
= =C2=A0=C2=A0 =C2=A0B() : a(1) { }
=C2=A0=C2=A0 =C2=A0void f2() {
=C2= =A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::cout << "A:" <&l= t; a.z << std::endl;
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0A = a;
};

---------------------------------------

Then yo= u need to create an inheritance for each class, since you need to cover a n= ew interface layer. Let's call C and D, where C uses the base class A a= nd D uses the base class B.

=C2=A0=C2=A0 member
A ---------> B=
|=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ||inheritance | inheritance
|=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0=C2=A0=C2=A0=C2=A0 |
v=C2=A0 member=C2=A0=C2=A0=C2=A0 v
C -----= ----> D

Code:
---------------------------------------
=
class A {
public:
=C2=A0=C2=A0 =C2=A0A(int z_) : z(z_) {=C2=A0=C2= =A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0int z;
};
class C: public A {
pu= blic:
=C2=A0=C2=A0 =C2=A0C(int y_) : y(y_), A(y_) {=C2=A0=C2=A0 =C2=A0}<= br>=C2=A0=C2=A0 =C2=A0long y;
};

class B {
public:
=C2=A0= =C2=A0 =C2=A0B() : a(1) { }
=C2=A0=C2=A0 =C2=A0void f2() {
=C2=A0=C2= =A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::cout << "A:" << a.z= << std::endl;
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0A a;
= };
class D: public B {
public:
=C2=A0=C2=A0 =C2=A0B() : a(3) { }=C2=A0=C2=A0 =C2=A0void f2() {
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0s= td::cout << "A:" << a.z << std::endl;
=C2=A0= =C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0C a;
};

--------------------= -------------------

Here where the problems appear, if you crea= te B you can access the data of A with the functions of B. But if you creat= e D, you access the data of C+A with the functions of D and C, but as soon = as you call the functions inherited from B, B can only access the data of A= that are totally in disuse, that is, create an instance in D generates in = memory a variable "a" with C+A, and also a variable "a"= with A , being in class D a C+A, A, where the last A is not used, only C+A= , in A it ends up using when the functions of B. are called.
=C2=A0 It i= s only possible to create a new virtual type function as the only case to a= ccess only C+A, but this generates junk code and in memory it reserves A as= garbage:

Code:
---------------------------------------
#= include <iostream>

class A {
public:
=C2=A0=C2=A0 =C2=A0= A(int z_) : z(z_) {=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0int z;
};<= br>
class C: public A {
public:
=C2=A0=C2=A0 =C2=A0C(int z_) : A(z= _) {=C2=A0=C2=A0 =C2=A0}
};

class B {
public:
=C2=A0=C2=A0 = =C2=A0B() : a(1) { }
=C2=A0=C2=A0 =C2=A0void f2() {
=C2=A0=C2=A0 =C2= =A0=C2=A0=C2=A0 =C2=A0std::cout << "A:" << get_C_a().= z << std::endl;
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0virtual= A const& get_C_a() { return a; }
=C2=A0=C2=A0 =C2=A0A a; // Use onl= y from B
};

class D : public B {
public:
=C2=A0=C2=A0 =C2= =A0D() : a(3) { }
=C2=A0=C2=A0 =C2=A0void f2(){
=C2=A0=C2=A0 =C2=A0= =C2=A0=C2=A0 =C2=A0std::cout << "C+A:" << a.z <<= ; std::endl;
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0B::f2();
=C2=A0=C2= =A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0C a; // Use C+A only from D
=C2=A0=C2= =A0 =C2=A0A const& get_C_a() override { return a; }
};

int ma= in() {
=C2=A0=C2=A0 =C2=A0B b; D d;
=C2=A0=C2=A0 =C2=A0b.f2(); d.f2()= ;
=C2=A0=C2=A0 =C2=A0return 0;
}

/* OUTPUT:
A:1
C+A:3A:3
*/

---------------------------------------

This = would be the best option, but not the ideal one. Ideally, "C a;" = of D replace "A a;" of B, in this way D only uses C+A from "= C a;" and B only uses A from "A a;"

This is my propos= al, a keyword like 'virtual' (or can be any other) in the variable = of the same name that is replaced by the variable definition of the base cl= ass.

Por ejemplo:
Code:
---------------------------------= ------
#include <iostream>

class A {
public:
=C2=A0= =C2=A0 =C2=A0A(int z_) : z(z_) {=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0= int z;
};

class C: public A {
public:
=C2=A0=C2=A0 =C2=A0C(= int z_) : A(z_) {=C2=A0=C2=A0 =C2=A0}
};

class B {
public:
= =C2=A0=C2=A0 =C2=A0B() : a(1) { }
=C2=A0=C2=A0 =C2=A0void f2() {
=C2= =A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::cout << "A:" <&l= t; a.z << std::endl;
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0vi= rtual A a; // Use A only from B
};

class D : public B {
public= :
=C2=A0=C2=A0 =C2=A0D() : a(3) { }
=C2=A0=C2=A0 =C2=A0void f2(){
= =C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::cout << "C+A:" &= lt;< a.z << std::endl;
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0B:= :f2();
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0virtual C a; // Use C+= A only from D
};

int main() {
=C2=A0=C2=A0 =C2=A0B b; D d;
= =C2=A0=C2=A0 =C2=A0b.f2(); d.f2();
=C2=A0=C2=A0 =C2=A0return 0;
}
=
/* OUTPUT:
A:1
C+A:3
A:3
*/

------------------------= ---------------

well this might not be possible, since compiled= the code, the binary code uses the data from an expected position in the v= ariables within the classes, so removing it from the list could alter the s= ize and position of the variables. On the other hand it would be possible, = since reserving memory from A or from C as C+A, generates a group of variab= les reserved in memories for each class even if it is C+A and calls functio= ns of A which omits C of C+A Just to have A in view, this could be an advan= tage.
I suggest some other option to simulate a replacement of variable = A by C.
If there is a better method that fulfills the same purpose witho= ut breaking with the basic structure proposed here then much better.
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

Tenemos 2 clases que contienen distin= tos conjuntos de datos, uno necesita usar las funciones y variables de otra= clase, por lo que se incluye como miembro apuntando a la otra clase:
=C2=A0=C2=A0 member
A -------> B

Code:
------------------= ---------------------

class A {
public:
=C2=A0=C2=A0 =C2= =A0A(int z_) : z(z_) {=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0int z;
= };

class B {
public:
=C2=A0=C2=A0 =C2=A0B() : a(1) { }
=C2= =A0=C2=A0 =C2=A0void f2() {
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::c= out << "A:" << a.z << std::endl;
=C2=A0=C2= =A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0A a;
};

-----------------------= ----------------

Luego se necesita crear una herencia para cada= clase, ya que necesita cubrir una nueva capa de interfaz. Llamemos C y D, = donde C usa la clase base A y D usa la clase base B.

=C2=A0=C2=A0 me= mber
A ---------> B
|=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0 |
|inheritance | inheritance
|=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 |
v=C2=A0 member=C2= =A0=C2=A0=C2=A0 v
C ---------> D

Code:
--------------------= -------------------

class A {
public:
=C2=A0=C2=A0 =C2=A0= A(int z_) : z(z_) {=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0int z;
};<= br>class C: public A {
public:
=C2=A0=C2=A0 =C2=A0C(int y_) : y(y_), = A(y_) {=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0long y;
};

clas= s B {
public:
=C2=A0=C2=A0 =C2=A0B() : a(1) { }
=C2=A0=C2=A0 =C2= =A0void f2() {
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::cout << = "A:" << a.z << std::endl;
=C2=A0=C2=A0 =C2=A0}
= =C2=A0=C2=A0 =C2=A0A a;
};
class D: public B {
public:
=C2=A0= =C2=A0 =C2=A0B() : a(3) { }
=C2=A0=C2=A0 =C2=A0void f2() {
=C2=A0=C2= =A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::cout << "A:" << a.z= << std::endl;
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0C a;
= };

---------------------------------------

=C2=A0 Aqui d= onde aparecen los problemas, si creas B puedes acceder a los datos de A con= las funciones de B. Pero si creas D, accedes a los datos de C+A con las fu= nciones de D y C, pero tan pronto llamas a las funciones heredadas de B, B = solo puede acceder a los datos de A que estan totalmente en desuso, es deci= r, crear una instancia en D genera en la memoria una variable "a"= con C+A, y tambien una variable "a" con A, siendo en la clase D = un C+A,A , donde la ultima A no se usa, solo C+A , en A se termina usando c= uando se llama a las funciones de B.
=C2=A0=C2=A0 =C2=A0Solo es posible = crear una nueva funcion tipo virtual como unico caso para acceder solamente= a C+A, pero esto genera codigo basura y en la memoria se reserva A como ba= sura:

Code:
---------------------------------------
#incl= ude <iostream>

class A {
public:
=C2=A0=C2=A0 =C2=A0A(in= t z_) : z(z_) {=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0int z;
};
<= br>class C: public A {
public:
=C2=A0=C2=A0 =C2=A0C(int z_) : A(z_) {= =C2=A0=C2=A0 =C2=A0}
};

class B {
public:
=C2=A0=C2=A0 =C2= =A0B() : a(1) { }
=C2=A0=C2=A0 =C2=A0void f2() {
=C2=A0=C2=A0 =C2=A0= =C2=A0=C2=A0 =C2=A0std::cout << "A:" << get_C_a().z &= lt;< std::endl;
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0virtual A = const& get_C_a() { return a; }
=C2=A0=C2=A0 =C2=A0A a; // Use only f= rom B
};

class D : public B {
public:
=C2=A0=C2=A0 =C2=A0D(= ) : a(3) { }
=C2=A0=C2=A0 =C2=A0void f2(){
=C2=A0=C2=A0 =C2=A0=C2=A0= =C2=A0 =C2=A0std::cout << "C+A:" << a.z << std:= :endl;
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0B::f2();
=C2=A0=C2=A0 = =C2=A0}
=C2=A0=C2=A0 =C2=A0C a; // Use C+A only from D
=C2=A0=C2=A0 = =C2=A0A const& get_C_a() override { return a; }
};

int main()= {
=C2=A0=C2=A0 =C2=A0B b; D d;
=C2=A0=C2=A0 =C2=A0b.f2(); d.f2();=C2=A0=C2=A0 =C2=A0return 0;
}

/* OUTPUT:
A:1
C+A:3
A:3=
*/

---------------------------------------

Esta seri= a la mejor opcion, pero no la ideal. Lo ideal es que "C a;" de D = remplace a "A a;" de B, de esta forma D solo usa C+A de "C a= ;" y B solo usa A de "A a;"

Esta es mi propuesta, una= palabra clave como 'virtual' (o puede ser cualquier otra) en la va= riable del mismo nombre que se remplace a la definicion de variable de la c= lase base.

Por ejemplo:
Code:
---------------------------------------
#include <iostream>

class A {
public:
= =C2=A0=C2=A0 =C2=A0A(int z_) : z(z_) {=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 = =C2=A0int z;
};

class C: public A {
public:
=C2=A0=C2=A0 = =C2=A0C(int z_) : A(z_) {=C2=A0=C2=A0 =C2=A0}
};

class B {
pub= lic:
=C2=A0=C2=A0 =C2=A0B() : a(1) { }
=C2=A0=C2=A0 =C2=A0void f2() {=
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::cout << "A:"= << a.z << std::endl;
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 = =C2=A0virtual A a; // Use A only from B
};

class D : public B {public:
=C2=A0=C2=A0 =C2=A0D() : a(3) { }
=C2=A0=C2=A0 =C2=A0void f= 2(){
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 =C2=A0std::cout << "C+A:= " << a.z << std::endl;
=C2=A0=C2=A0 =C2=A0=C2=A0=C2=A0 = =C2=A0B::f2();
=C2=A0=C2=A0 =C2=A0}
=C2=A0=C2=A0 =C2=A0virtual C a; /= / Use C+A only from D
};

int main() {
=C2=A0=C2=A0 =C2=A0B b; = D d;
=C2=A0=C2=A0 =C2=A0b.f2(); d.f2();
=C2=A0=C2=A0 =C2=A0return 0;<= br>}

/* OUTPUT:
A:1
C+A:3
A:3
*/

----------------= -----------------------

bien esto podria no ser posible, ya que= compilado el codigo, el codigo binario utiliza los datos desde una posicio= n esperada en las variables dentro de las clases, por lo que eliminarlo de = la lista podria alterar el tama=C3=B1o y la posicion de las variables. Por = otro lado seria posible, ya que reservar memoria desde A o desde C como C+A= , se genera un grupo de variables reservadas en memorias para cada clase in= cluso si es C+A y llamar a funciones de A lo cual omite C de C+A solo para = tener a la vista A, podria ser esto una ventaja.
Sugiero alguna otra opc= ion para simular un remplazo de la variable A por C.
Si existe algun met= odo mejor que cumpla con el mismo proposito sin romper con la estructura ba= sica propuesta aqui entonces mucho mejor.

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