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Re: duct typing and interface in C++

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TP wrote:
> Hello,
>
> I convert a Python/Qt program (PyQt) in C++/Qt.
> The programmer has used the duck typing of Python, thus I would like to have
> duck typing in C++, in fact exactly what is described in the "best answer"
> at the following address:
>
> http://stackoverflow.com/questions/289176/how-is-duck-typing-different-from-
> the-old-variant-type-and-or-interfaces
>
> (the "best answer" is the second post of the page, the one with a green
> sign).
>
> Is it possible in C++?
>
> Thanks in advance,
>
> TP

I've tried just for fun. This is probably a naive
imitation... I just used codepad therefore had
no other libraries (e.g. boost available).

Output:

Duffy quacked!
Donald quacked!

//code...
#include <iostream>
#include <algorithm>

class Duck
{
     struct QuackIF
     {
       virtual void quack() = 0;
       virtual QuackIF* clone() const = 0;
       virtual ~QuackIF(){}
     };

     template <class T>
     struct QuackImpl : QuackIF
     {
       typedef void (T::*QuackFunc)();
       QuackImpl( T& receiver )
       : receiver_( &receiver ),
         f_( &T::quack )
       {
       }
       virtual QuackIF* clone() const
       {
         return new QuackImpl( *this );
       }

       virtual void quack()
       {
         (receiver_->*f_)();//Quack!!!
       }
       virtual ~QuackImpl(){}
       private:
         T* receiver_;
         QuackFunc f_;
     };
     QuackIF* duck_;

     public:
       Duck( const Duck& other )
       : duck_( other.duck_ ? other.duck_->clone() : 0 )
       {
       }
       ~Duck(){ delete duck_; }

       Duck& operator=( Duck other )
       {
         std::swap( other.duck_, duck_ ); return *this;
       }

       template <class DuckT>
       Duck( DuckT* duck )
       : duck_( new QuackImpl<DuckT>( *duck ) )
       {
       }

       void quack()
       {
         if( duck_ ){ duck_->quack(); }
         else
         {
           std::cout << "Quack!" << std::endl;
         }
       }
};

struct Daffy
{
   void quack(){ std::cout << "Duffy quacked!" << std::endl; }
};

struct Donald
{
   void quack(){ std::cout << "Donald quacked!" << std::endl; }
};

int main()
{
   Duck duck = new Daffy;
   duck.quack();
   duck = new Donald;
   duck.quack();
}

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Thread

duct typing and interface in C++ TP <Tribulations@Paralleles.invalid> - 2011-07-24 17:40 +0200
  Re: duct typing and interface in C++ Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2011-07-24 18:11 +0200
    Re: duct typing and interface in C++ Marcel Müller <news.5.maazl@spamgourmet.org> - 2011-07-25 00:03 +0200
      Re: duct typing and interface in C++ Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2011-07-25 10:11 +0200
      Re: duct typing and interface in C++ Goran <goran.pusic@gmail.com> - 2011-07-25 04:18 -0700
  Re: duct typing and interface in C++ Nobody <nobody@nowhere.com> - 2011-07-24 17:39 +0100
    Re: duct typing and interface in C++ TP <Tribulations@Paralleles.invalid> - 2011-07-24 19:55 +0200
      Re: duct typing and interface in C++ Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2011-07-24 20:11 +0200
        Re: duct typing and interface in C++ TP <Tribulations@Paralleles.invalid> - 2011-07-24 20:23 +0200
          Re: duct typing and interface in C++ Dombo <dombo@disposable.invalid> - 2011-07-24 20:45 +0200
          Re: duct typing and interface in C++ Alain Ketterlin <alain@dpt-info.u-strasbg.fr> - 2011-07-24 21:10 +0200
          Re: duct typing and interface in C++ Nobody <nobody@nowhere.com> - 2011-07-24 21:21 +0100
            Re: duct typing and interface in C++ TP <Tribulations@Paralleles.invalid> - 2011-07-24 23:50 +0200
              Re: duct typing and interface in C++ Stuart Redmann <DerTopper@web.de> - 2011-07-24 23:33 -0700
                Re: duct typing and interface in C++ TP <Tribulations@Paralleles.invalid> - 2011-07-25 23:00 +0200
              Re: duct typing and interface in C++ Paavo Helde <myfirstname@osa.pri.ee> - 2011-07-25 01:35 -0500
              Re: duct typing and interface in C++ Goran <goran.pusic@gmail.com> - 2011-07-25 04:10 -0700
          Re: duct typing and interface in C++ James Kanze <james.kanze@gmail.com> - 2011-07-30 11:51 -0700
      Re: duct typing and interface in C++ Dombo <dombo@disposable.invalid> - 2011-07-24 20:21 +0200
        Re: duct typing and interface in C++ Dombo <dombo@disposable.invalid> - 2011-07-24 20:26 +0200
  Re: duct typing and interface in C++ Dombo <dombo@disposable.invalid> - 2011-07-24 18:36 +0200
    Re: duct typing and interface in C++ BGB <cr88192@hotmail.com> - 2011-07-24 10:02 -0700
  Re: duct typing and interface in C++ BGB <cr88192@hotmail.com> - 2011-07-24 09:45 -0700
    Re: duct typing and interface in C++ TP <Tribulations@Paralleles.invalid> - 2011-07-24 20:15 +0200
      Re: duct typing and interface in C++ BGB <cr88192@hotmail.com> - 2011-07-24 14:06 -0700
  Re: duct typing and interface in C++ Thomas Boell <tboell@domain.invalid> - 2011-07-25 02:05 +0200
  Re: duct typing and interface in C++ Qi <no@no.no> - 2011-07-25 09:54 +0800
  Re: duct typing and interface in C++ Werner Erasmus <werasm@gmail.com> - 2011-07-25 23:36 +0200
    Re: duct typing and interface in C++ Leigh Johnston <leigh@i42.co.uk> - 2011-07-25 23:22 +0100
      Re: duct typing and interface in C++ Werner Erasmus <werasm@gmail.com> - 2011-07-26 08:35 +0200

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