PRODUCT  :  Borland C++                           NUMBER  :  1543
  VERSION  :  All
       OS  :  All
     DATE  :  October 25, 1993                         PAGE  :  1/2

    TITLE  :  Class manipulator example




  // Making your own manipulator with your own class

  #include <iostream.h>
  #include <strstream.h>

  class m_stream: public ostrstream
  {
      public:
      char buffer[458];
      m_stream() : ostrstream(buffer, sizeof(buffer)) {}
      friend m_stream& output(m_stream&);
      friend m_stream& operator << ( m_stream&, const char *);
      friend m_stream& operator << ( m_stream& m,
      m_stream& (*f)(m_stream&) );
  };

  // We need to re-do all of ostream so that the operators will
  // return m_stream references rather than ostream &'s
  // Our m_stream operators simply call the base class operators
  // The m_stream operators can be modified to add extended
  // functionality

  inline m_stream& ends(m_stream& m)
  {
      (ostream &) m << ends;
      return m;
  }

  inline m_stream& operator << ( m_stream & m, const char * k)
  {
      (ostream &) m << k;
      return m;
  }

  // Now we can use our own operator << ( taking function pointer)
  // to use a manipulator specialized for m_stream operations.
  // This avoids any casts from ostream& to m_stream&, which
  // would be dangerous. (casting m_stream& to ostream& won't
  // hurt.)

  m_stream& operator << ( m_stream& m,
  m_stream& (*f)(m_stream&) )
  {













  PRODUCT  :  Borland C++                           NUMBER  :  1543
  VERSION  :  All
       OS  :  All
     DATE  :  October 25, 1993                         PAGE  :  2/2

    TITLE  :  Class manipulator example




      return f(m);
  }

  // And here is the manipulator in question, which ends up
  // being called by the function above through a function
  // pointer when we use it.

  m_stream& output(m_stream& m)
  {
      // do the appropriate output operation here.
      // m.str() returns m's string
      cout << m.str();
      m.seekp(0);  // "flush" by rewinding to 0
      return m;
  }

  int main()
  {
      m_stream mout;
      mout << "This is the test.\n" << ends << output;
      mout << "Test Line 2.\n" << ends << output;
      return 0;
  }


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