Re: [boost] **** SPAM ****Re: manipulators for filtering_stream s

From: Larry Evans (cppljevans_at_[hidden])
Date: 2008-03-01 10:50:07

On 03/01/08 09:40, Roland Schwarz wrote:
> Larry Evans wrote:
>> I couldn't resist trying it now;
> ;-)
> 
>> however, I'm getting wrong output :(
> 
> Hmm,  I did not test it, but from looking at your source:
> 
> marg_ostream& mout(void)
> {
>     return std::cout;
> }
> 
> gives you back std::cout, while it should hand back
>   ; boost::iostreams::filtering_ostream out
> 
> The state is stored in out instance of course,
> not cout.
> 
Right.  So, should:

<-- cut here --
#include "indent.hpp"
typedef boost::iostreams::filtering_ostream marg_ostream;
marg_ostream out;
#include <iostream>
marg_ostream& mout(void)
{
     return out;
}
//#define DEBUG_PRINT
void operator++(marg_ostream& sout)
{
     #ifdef DEBUG_PRINT
     sout<<"operator++(marg_ostream&)\n";
     #endif
     sout<<indent_in;
}
void operator--(marg_ostream& sout)
{
     sout<<indent_out;
     #ifdef DEBUG_PRINT
     sout<<"operator--(marg_ostream&)\n";
     #endif
}
...
int main(void)
   {
   ; indent_filter::push(out,2)
   ; out.push(std::cout)
   ; mout()<<"line1\n"
...
 >-- cut here --
work?  With this change, I get compile errors like:

indent_test.cpp: In function 'marg_ostream& operator<<(marg_ostream&, 
const test*)':
indent_test.cpp:60: error: no match for 'operator<<' in 'std::operator<< 
[with _Traits = std::char_traits<char>](((std::basic_ostream<char, 
std::char_traits<char> 
 >&)(&((marg_ostream*)sout)->boost::iostreams::filtering_stream<boost::iostreams::output, 
char, std::char_traits<char>, std::allocator<char>, 
boost::iostreams::public_>::<anonymous>.boost::iostreams::detail::filtering_stream_base<boost::iostreams::chain<boost::iostreams::output, 
char, std::char_traits<char>, std::allocator<char> >, 
boost::iostreams::public_>::<anonymous>)), ((const char*)"*(test*)=")) 
<< * a_test'
/usr/include/c++/4.1.3/bits/ostream.tcc:67: note: candidates are: 
std::basic_ostream<_CharT, _Traits>& std::basic_ostream<_CharT, 
_Traits>::operator<<(std::basic_ostream<_CharT, _Traits>& 
(*)(std::basic_ostream<_CharT, _Traits>&)) [with _CharT = char, _Traits 
= std::char_traits<char>]