Is this error report indicating that I have a problem in my use of boost or my code? Here is the statement that its trying to compile: output << boost::format("%1X") % boost::io::group ( std::hex, std::setw(2), std::setfill('0'), static_cast<boost::uint16_t>(m_data[(*pos).second])); m_data is defined as: // !\brief This type represents a byte typedef boost::uint8_t data_t; // !\brief The internal data structure of a Memory Map typedef std::vector <data_t> Values_t; data_types::Memory_Map::Values_t m_data; pos is a data_types::Memory_Map::Address_Map_t::const_iterator that is defined as: // !\brief Map key is a 32-bit address in memory typedef boost::uint32_t map_key_t; // !\brief index where the data is in the Values_t list typedef boost::uint32_t index_t; // !\brief Table use for normal lookups ( address => index ) typedef std::map<map_key_t, index_t> Address_Map_t; Please forgive my ignorance here of Visual Studio. I have read up the microsoft explaination of this error but I have trouble understanding where to start looking. I do not have any constant data members in my code for the Memory_Map class. Therefore I am not sure why I am getting this error. Stephen ------ Build started: Project: data_containers, Configuration: Debug Win32 ------ 1>Compiling... 1>Memory_Map.cpp 1>C:\Program Files\boost\boost_1_33_1\boost/format/group.hpp(124) : warning C4512: 'boost::io::detail::group4<T1,T2,T3,T4>' : assignment operator could not be generated 1> with 1> [ 1> T1=std::ios_base &(__cdecl *)(std::ios_base &), 1> T2=std::_Smanip<std::ios_base::fmtflags>, 1> T3=std::_Fillobj<char>, 1> T4=const boost::uint16_t & 1> ] 1> C:\Program Files\boost\boost_1_33_1\boost/format/group.hpp(54) : see reference to class template instantiation 'boost::io::detail::group4<T1,T2,T3,T4>' being compiled 1> with 1> [ 1> T1=std::ios_base &(__cdecl *)(std::ios_base &), 1> T2=std::_Smanip<std::ios_base::fmtflags>, 1> T3=std::_Fillobj<char>, 1> T4=const boost::uint16_t & 1> ] 1> .\Memory_Map.cpp(341) : see reference to class template instantiation 'boost::io::detail::group1<T1>' being compiled 1> with 1> [ 1> T1=boost::io::detail::group4<std::ios_base &(__cdecl *)(std::ios_base &),std::_Smanip<std::ios_base::fmtflags>,std::_Fillobj<char>,const boost::uint16_t &> 1> ] 1>C:\Program Files\boost\boost_1_33_1\boost/format/group.hpp(58) : warning C4512: 'boost::io::detail::group1<T1>' : assignment operator could not be generated 1> with 1> [ 1> T1=boost::io::detail::group4<std::ios_base &(__cdecl *)(std::ios_base &),std::_Smanip<std::ios_base::fmtflags>,std::_Fillobj<char>,const boost::uint16_t &> 1> ] 1>C:\Program Files\boost\boost_1_33_1\boost/format/group.hpp(58) : warning C4512: 'boost::io::detail::group1<T1>' : assignment operator could not be generated 1> with 1> [ 1> T1=const boost::uint16_t & 1> ] 1> C:\Program Files\boost\boost_1_33_1\boost/format/feed_args.hpp(103) : see reference to class template instantiation 'boost::io::detail::group1<T1>' being compiled 1> with 1> [ 1> T1=const boost::uint16_t & 1> ] 1> C:\Program Files\boost\boost_1_33_1\boost/format/feed_args.hpp(150) : see reference to function template instantiation 'void boost::io::detail::put_last<char,std::char_traits<char>,boost::io::detail::group4<T1,T2,T3,T4>>(std::basic_ostream<_Elem,_Traits> &,const boost::io::detail::group1<boost::io::detail::group4<T1,T2,T3,T4>> &)' being compiled 1> with 1> [ 1> T1=std::ios_base &(__cdecl *)(std::ios_base &), 1> T2=std::_Smanip<std::ios_base::fmtflags>, 1> T3=std::_Fillobj<char>, 1> T4=const boost::uint16_t &, 1> _Elem=char, 1> _Traits=std::char_traits<char> 1> ] 1> C:\Program Files\boost\boost_1_33_1\boost/format/feed_args.hpp(242) : see reference to function template instantiation 'void boost::io::detail::put<Ch,Tr,Alloc,T>(T,const boost::io::detail::format_item<Ch,Tr,Alloc> &,std::basic_string<_Elem,_Traits,_Ax> &,boost::io::basic_altstringbuf<Ch,Tr,Alloc> &,boost::io::detail::locale_t *)' being compiled 1> with 1> [ 1> Ch=char, 1> Tr=std::char_traits<char>, 1> Alloc=std::allocator<char>, 1> T=const boost::io::detail::group1<boost::io::detail::group4<std::ios_base &(__cdecl *)(std::ios_base &),std::_Smanip<std::ios_base::fmtflags>,std::_Fillobj<char>,const boost::uint16_t &>> &, 1> _Elem=char, 1> _Traits=std::char_traits<char>, 1> _Ax=std::allocator<char> 1> ] 1> C:\Program Files\boost\boost_1_33_1\boost/format/feed_args.hpp(251) : see reference to function template instantiation 'void boost::io::detail::distribute<Ch,Tr,Alloc,T>(boost::basic_format<Ch> &,T)' being compiled 1> with 1> [ 1> Ch=char, 1> Tr=std::char_traits<char>, 1> Alloc=std::allocator<char>, 1> T=const boost::io::detail::group1<boost::io::detail::group4<std::ios_base &(__cdecl *)(std::ios_base &),std::_Smanip<std::ios_base::fmtflags>,std::_Fillobj<char>,const boost::uint16_t &>> & 1> ] 1> C:\Program Files\boost\boost_1_33_1\boost/format/format_class.hpp(64) : see reference to function template instantiation 'boost::basic_format<Ch> &boost::io::detail::feed<char,Tr,Alloc,const T&>(boost::basic_format<Ch> &,const boost::io::detail::group1<T1>)' being compiled 1> with 1> [ 1> Ch=char, 1> Tr=std::char_traits<char>, 1> Alloc=std::allocator<char>, 1> T=boost::io::detail::group1<boost::io::detail::group4<std::ios_base &(__cdecl *)(std::ios_base &),std::_Smanip<std::ios_base::fmtflags>,std::_Fillobj<char>,const boost::uint16_t &>>, 1> T1=boost::io::detail::group4<std::ios_base &(__cdecl *)(std::ios_base &),std::_Smanip<std::ios_base::fmtflags>,std::_Fillobj<char>,const boost::uint16_t &> 1> ] 1> .\Memory_Map.cpp(341) : see reference to function template instantiation 'boost::basic_format<Ch> &boost::basic_format<Ch>::operator %<boost::io::detail::group1<T1>>(const T &)' being compiled 1> with 1> [ 1> Ch=char, 1> T1=boost::io::detail::group4<std::ios_base &(__cdecl *)(std::ios_base &),std::_Smanip<std::ios_base::fmtflags>,std::_Fillobj<char>,const boost::uint16_t &>, 1> T=boost::io::detail::group1<boost::io::detail::group4<std::ios_base &(__cdecl *)(std::ios_base &),std::_Smanip<std::ios_base::fmtflags>,std::_Fillobj<char>,const boost::uint16_t &>> 1> ]