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";
 }

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

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++