Re: ostream constructor error

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Julian wrote:
> I have this piece of code that is working fine in VC6... but when i
> tried to compile the same code in VC++.NET, I am getting this error :
>
> error C2512: 'std::basic_ostream<_Elem,_Traits>' : no appropriate
> default constructor available
>        with
>        [
>            _Elem=char,
>            _Traits=std::char_traits<char>
>        ]
>
> i had also changed #include <fstream.h> to #include <fstream>
> and added this line "using namespace std;"
Ok, but do you understand why these changes are necessary? VC6 used a 
non-standard "stream" implementation, whereas CV7 conforms to what is 
dictated in the C++ standard concerning streams. The documentation for 
standard ostream is here :
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcstdlib/html/vclrf_ostream_Ostream.asp?frame=true
It shows us that std::ostream is really a typedef for 
std::basic_ostream<char>, and the only constructor for this typeis defined 
here : 
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcstdlib/html/vclrf_ostream_basicostreambasicostream.asp?frame=true
As you can see, the constructor needs a basic_streambuf argument. Therefore, 
you need to provide a streambuf for the constructin of the base clas ostream 
of your ArgumentOstream class. Not knowing your whole code,I can't be sure, 
but U guess your constructor should be :

ArgumentOstream(Arguments &args, ostream &o=cout)

: ostream(o.rdbuf())
{
  //no call to init : it is done through the base class constructor
  //...
}

Arnaud
MVP - VC


.

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