Thread: setw() type of overloaded <<

I am creating a socket output class so I can use << to send data to a socket. I've gotten the major parts to work and I am now onto adding in some other stuff I want like setw(), precision(), etc.

I've already gotten endl done by setting up an overloaded << to accept a pointer to a function, call the function, which then executes the proper code. All nice an easy.

My current problem is with trying to setup a precision(). I want to be able to do:

Code:

sendsock<<precision(5)<<20.837492;

but for the life of me I can not figure out how to setup the operator << to accept the correct parameters.

class defination:

Code:

class SocketOut {
  int sock;
  unsigned prec;
  public:
    SocketOut(int x) { sock = x; prec = 3;}

    inline const SocketOut& operator << (
        const SocketOut & (*f)(SocketOut &, unsigned int)
    ){
      return f(*this,x);
    }


    inline const SocketOut& operator <<
      (const SocketOut & (*f)(const SocketOut &) ) const{
        return f(*this);
    }

    const SocketOut& operator << (unsigned char) const;

    const SocketOut& operator << (unsigned char *) const;

    const SocketOut& operator << (char x) const {
      return (*this)<<(unsigned char)x;
    }

    const SocketOut& operator << (char *x) const{
      return (*this)<<(unsigned char *)x;
    }

    const SocketOut& operator << (int) const;

    const SocketOut& operator << (double) const;

    const SocketOut& operator << (float x) const{
      return (*this)<<(double)x;
    }

    const SocketOut& precision (unsigned x){
      prec = x;
      return *this;
    }

};

Non-member functions that are used:

Code:

 inline const SocketOut &endl (const SocketOut &x){
  return x<<(unsigned char *)"\r\n";
}
inline const SocketOut &precision (SocketOut &x, unsigned int y) {
  return x.precision(y);
}

The other member functions aren't really needed for this problem.

I've tried:

Code:

    inline const SocketOut& operator << (
        const SocketOut & (*f)(SocketOut &, unsigned int), unsigned x
    ){
      return f(*this,x);
    }

but it complains that operator << can only take one parameter. I've also tried various other attempts without success.

I know pointers to functions are one of my weaker areas so I would appreciate any help you could lend me.

Thanks

Thanks Prelude. That actually clarifies what iomanip.h was doing with its #defines for setw and such

Oh:

Code:

struct argmanip {
  unsigned int x;
public:

go into the SocketOut class defination correct?

Thanks again

Gonna need a wee bit more help

new definations (with unrelavent member functions removed )

Code:

class SocketOut;

struct argmanip {
  unsigned int x;

  public:
    const SocketOut& (*f)(SocketOut&, unsigned int);

    argmanip(const SocketOut& (*func)(SocketOut&, unsigned int), unsigned int init)
          : x(init)
          , f(func)
       {}
};

class SocketOut {
  int sock;
  unsigned prec;

  public:

    SocketOut(int x) { sock = x; prec = 3;}

    inline const SocketOut& operator << (
         const argmanip& manip //Had to add const to suppress warnings
    ){
      return manip.f(*this,manip.x);
    }

    inline const SocketOut& operator <<
      (const SocketOut & (*f)(const SocketOut &) ) const{
        return f(*this);
    }
    const SocketOut& operator << (double) const;

    const SocketOut& operator << (float x) const{
      return (*this)<<(double)x;
    }
};

inline const SocketOut& precision( SocketOut& x, unsigned int y ){
  return x.precision(y);
}

inline argmanip precision( unsigned int y ){
      return argmanip(precision, y);
}

now this works fine for:

Code:

sendsock<<precision(2)<<1234.827;

But i get the following warning for

Code:

sendsock<<12345.67890<<precision(2)<<1234.827;

passing `const SocketOut' as `this' argument of `const class SocketOut & SocketOut:perator <<(const argmanip &)' discards qualifiers

How would I cast away const in this situation?

You have to simplify things don't you
Heh was just following the example from iostream

Ok I did remove all the consts save one. If I didn't have:

Code:

inline SocketOut& operator<< ( const argmanip& manip ) /*...*/

I recieved the following error:

Code:

game.cpp:22: initialization of non-const reference type `struct argmanip &'
game.cpp:22: from rvalue of type `argmanip'
socket.h:42: in passing argument 1 of `SocketOut::operator <<(argmanip &)

But it all works now. Thanks for the help