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Groups > comp.lang.c++ > #13555

Re: static_cast and std::vector

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>> #include<vector>
>>
>> class Base {};
>> class Derived0 : public Base {};
>> class Derived1 : public Base {};
>>
>> class Y
>> {
>>     std::vector<Base*>  m_vb[2];
>>
>>     public:
>>
>>     void Add(Derived0* d0) { m_vb[0].push_back(d0); }
>>     void Add(Derived1* d1) { m_vb[1].push_back(d1); }
>>
>>     const std::vector<Derived0*>* GetD0()
>> 	{ return (const std::vector<Derived0*>*)&m_vb[0]; }
>>     const std::vector<Derived1*>* GetD1()
>> 	{ return (const std::vector<Derived1*>*)&m_vb[1]; }
>>
>>     const std::vector<Derived0*>* GetDD0()
>> 	{ return static_cast<const std::vector<Derived0*>*>(&m_vb[0]); }
>>     const std::vector<Derived1*>* GetDD1()
>> 	{ return static_cast<const std::vector<Derived1*>*>(&m_vb[1]); }
>>
>> };
>
> Why don't you just write:
> std::vector<Derived0*>  m_vd0;
> std::vector<Derived1*>  m_vd1;
> and use those without any casting?
>
> This would be the most obvious solution and you are losing nothing.

We have looked into this, but we also really need functionality like

   const std::vector<Base*>* GetBase(int which)
  	{ return &m_vb[which]; }

So, changing as you suggested would preclude this.  Would it be possible 
to replace the UB casts

      const std::vector<Derived0*>* GetD0()
  	{ return (const std::vector<Derived0*>*)&m_vb[0]; }
      const std::vector<Derived1*>* GetD1()
  	{ return (const std::vector<Derived1*>*)&m_vb[1]; }

with some type of specialized iterator?

Thanks.

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static_cast and std::vector john <gh14tq5@yahoo.com> - 2012-01-20 08:56 -0500
  Re: static_cast and std::vector Leigh Johnston <leigh@i42.co.uk> - 2012-01-20 14:00 +0000
    Re: static_cast and std::vector john <gh14tq5@yahoo.com> - 2012-01-20 09:58 -0500
      Re: static_cast and std::vector Leigh Johnston <leigh@i42.co.uk> - 2012-01-20 15:02 +0000
        Re: static_cast and std::vector john <gh14tq5@yahoo.com> - 2012-01-20 10:28 -0500
      Re: static_cast and std::vector "Fred Zwarts \(KVI\)" <F.Zwarts@KVI.nl> - 2012-01-20 16:48 +0100
        Re: static_cast and std::vector Leigh Johnston <leigh@i42.co.uk> - 2012-01-20 16:02 +0000
          Re: static_cast and std::vector Joshua Maurice <joshuamaurice@gmail.com> - 2012-01-20 14:30 -0800
      Re: static_cast and std::vector Juha Nieminen <nospam@thanks.invalid> - 2012-01-20 19:04 +0000
  Re: static_cast and std::vector Tobias Müller <troplin@bluewin.ch> - 2012-01-21 08:56 +0000
    Re: static_cast and std::vector john <gh14tq5@yahoo.com> - 2012-01-23 12:47 -0500
      Re: static_cast and std::vector Ian Collins <ian-news@hotmail.com> - 2012-01-24 09:22 +1300
  Re: static_cast and std::vector Pavel <pauldontspamtolk@removeyourself.dontspam.yahoo> - 2012-01-21 23:02 -0500

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