• dark777 (88/88) Dec 14 2017 I know that this community is not from c ++, but for some time I
• Biotronic (12/25) Dec 15 2017 I expect it's confused by __cdecl. I just copied the function
• dark777 (3/30) Dec 15 2017 I do not use windows I thought it was the standard of iostream

dark777 <jeanzonta777 yahoo.com.br> writes:

I know that this community is not from c ++, but for some time I 
studied how to do overload of ostream operators in c ++ and I 
even managed to get to this result, I got to this result in 
another post done here but I did not understand the that it 
returns this error below:


bin2.cxx:44:43: error: expected ‘,’ or ‘...’ before ‘(’ token
    std::ostream& operator<<(std::ios_base& (__cdecl 
*_Pfn)(std::ios_base&))
                                            ^
bin2.cxx: In member function ‘std::ostream& 
BinStream::operator<<(std::ios_base&)’:
bin2.cxx:46:16: error: ‘_Pfn’ was not declared in this scope
     return os <<_Pfn;

so that the output is the same as below:

         127 em binario:     0001111111
         127 em octal:       177
         127 em binario:     0001111111
         127 em hexadecimal: 7f
         127 em decimal:     127
         127 em binario:     0001111111

and not this:

         127 em binario:     0001111111
         127 em octal:       0001111111
         127 em binario:     0001111111
         127 em hexadecimal: 0001111111
         127 em decimal:     0001111111
         127 em binario:     0001111111


#include <ios> //ios_base
#include <sstream>
#include <climits>   // CHAR_BIT
#include <iostream>
#include <algorithm> // reverse

     struct BinStream
    {
          std::ostream& os;
          BinStream(std::ostream& os) : os(os) {}

      std::string binario(unsigned int n)
      {
       //converte numero para string de bits
       std::stringstream bitsInReverse;
       //int nBits = sizeof(n) * CHAR_BIT;
       unsigned int nBits = sizeof(n)*2.5;

       while (nBits-- > 0)
       {
        bitsInReverse << (n & 1);
        n >>= 1;
       }

       std::string bits(bitsInReverse.str());
       std::reverse(bits.begin(), bits.end());
       return bits;
      }

          template<class T>
          BinStream& operator<<(T&& value)
          {
              os << value;
              return *this;
          }

          BinStream& operator<<(int value)
          {
              os << binario(value);
              return *this;
          }

          std::ostream& operator<<(std::ios_base& (__cdecl 
*_Pfn)(std::ios_base&))
          {
              return os << _Pfn;
          }
      };

      struct Bin
      {
          friend BinStream operator<<(std::ostream& os, const Bin& 
f);
      } bin;

      BinStream operator<<(std::ostream& os, const Bin& f)
      {
          return BinStream(os);
      }

  int main()
  {
   std::cout << "\n\t127 em binario:     " << binario(127)
             << "\n\t127 em binario:     " << bin << 127
             << "\n\t127 em octal:       " << std::oct << 127
             << "\n\t127 em binario:     " << bin << 127
             << "\n\t127 em hexadecimal: " << std::hex << 127
             << "\n\t127 em binario:     " << bin << 127
             << "\n\t127 em decimal:     " << std::dec << 127
             << "\n\t127 em binario:     " << bin << 127 << "\n\n";
  }

Biotronic <simen.kjaras gmail.com> writes:

On Thursday, 14 December 2017 at 22:47:15 UTC, dark777 wrote:
 I know that this community is not from c ++, but for some time 
 I studied how to do overload of ostream operators in c ++ and I 
 even managed to get to this result, I got to this result in 
 another post done here but I did not understand the that it 
 returns this error below:


 bin2.cxx:44:43: error: expected ‘,’ or ‘...’ before ‘(’ token
    std::ostream& operator<<(std::ios_base& (__cdecl 
 *_Pfn)(std::ios_base&))
                                            ^
 bin2.cxx: In member function ‘std::ostream& 
 BinStream::operator<<(std::ios_base&)’:
 bin2.cxx:46:16: error: ‘_Pfn’ was not declared in this scope
     return os <<_Pfn;

I expect it's confused by __cdecl. I just copied the function 
declaration from VS' iostreams, so it might be tainted by how VS 
does things. Removing __cdecl might work, or just add
#define __cdecl __attribute__((__cdecl__))
A third option is to replace `std::ios_base& (__cdecl 
*Pfn)(std::ios_base&)` with `decltype(std::hex)& Pfn`.

All of this said, I'd suggest finding a C++ forum to get answers 
to these questions. While I'm happy to help, it's not really the 
place for these discussions.

--
   Biotronic

dark777 <jeanzonta777 yahoo.com.br> writes:

On Friday, 15 December 2017 at 08:57:23 UTC, Biotronic wrote:
 On Thursday, 14 December 2017 at 22:47:15 UTC, dark777 wrote:
 I know that this community is not from c ++, but for some time 
 I studied how to do overload of ostream operators in c ++ and 
 I even managed to get to this result, I got to this result in 
 another post done here but I did not understand the that it 
 returns this error below:


 bin2.cxx:44:43: error: expected ‘,’ or ‘...’ before ‘(’ token
    std::ostream& operator<<(std::ios_base& (__cdecl 
 *_Pfn)(std::ios_base&))
                                            ^
 bin2.cxx: In member function ‘std::ostream& 
 BinStream::operator<<(std::ios_base&)’:
 bin2.cxx:46:16: error: ‘_Pfn’ was not declared in this scope
     return os <<_Pfn;

 I expect it's confused by __cdecl. I just copied the function 
 declaration from VS' iostreams, so it might be tainted by how 
 VS does things. Removing __cdecl might work, or just add
 #define __cdecl __attribute__((__cdecl__))
 A third option is to replace `std::ios_base& (__cdecl 
 *Pfn)(std::ios_base&)` with `decltype(std::hex)& Pfn`.

 All of this said, I'd suggest finding a C++ forum to get 
 answers to these questions. While I'm happy to help, it's not 
 really the place for these discussions.

 --
   Biotronic

I do not use windows I thought it was the standard of iostream 
ansi c++