Hello, when compiling <boost/algorithm/string/trim.hpp> with MSVC 7.1 at maximal warning level you get a warning 4512 ("assignment operator could not be generated") because of the const members in struct is_classifiedF from boost/algorithm/string/detail/classification.hpp. The trivial patch below fixes it. Notice that I didn't take the assignment operator in "#ifdef _MSC_VER" because I see no harm in doing this for all compilers but then no other compiler I know about gives such warning so it should be also safe to add the #ifdef if this is preferred. *** classification.hpp.orig Wed Aug 17 10:19:50 2005 --- classification.hpp Wed Aug 17 10:19:46 2005 *************** *** 55,60 **** --- 55,64 ---- #endif private: + // prevent compiler from trying to generate this operator + // automatically (and failing because of const members) + is_classifiedF& operator=(const is_classifiedF&); + const std::ctype_base::mask m_Type; const std::locale m_Locale; }; Thanks in advance, VZ