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From:	"Anthony" <akantsel AT integra DOT rmt DOT ru>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Why does this code fails?
Date:	Thu, 11 Mar 2004 14:11:07 +0300
Organization:	Radio-MSU NOC, Moscow State University
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#include <iostream>
#include <stdexcept>
#include <fstream>

class mystream {
 private:
 std::ostream *pstream;
 public:
 mystream(std::ostream& s) : pstream(&s) {}
 mystream() : pstream(NULL) {}

 operator std::ostream&() throw(std::runtime_error)
 {
  if(pstream) {
   return *pstream;
  } else {
   throw std::runtime_error("Convertion of NULL stream.");
  }
 }
void assign(std::ostream& s);
...
};

mystream mstr;

int main()
{
 mstr.assign(std::cout);
 try{
  static_cast<std::ostream&>(mstr) << "Hello world";    // This compiles
fine
  mstr << "Hello world";                                                //
This gives error 'no match for operator<< 'in mstr << "Hello world"'
 }
 catch(std::runtime_error& err) {
  std::cerr << "\n ERROR: " << err.what();
 }
 std::cin.get();
 return 0;
}
-------------------------------------
Why doesn't convertion by default work? How to make it work with no
cast-ing?
The goal is to have a global static reference to a stream, where some code
can do output and another code can change this output destanation, like make
it go to cout, then after sometime to a file stream, etc. Is there better
way to do this than this code?
Thanks.

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