123.cpp:5: error: no matching function for call to 'std::basic_ifstream<char, std::char_traits<char> >::basic_ifstream(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)' /usr/include/c++/4.4/fstream:454: note: candidates are: std::basic_ifstream<_CharT, _Traits>::basic_ifstream(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>] /usr/include/c++/4.4/fstream:440: note: std::basic_ifstream<_CharT, _Traits>::basic_ifstream() [with _CharT = char, _Traits = std::char_traits<char>] /usr/include/c++/4.4/iosfwd:81: note: std::basic_ifstream<char, std::char_traits<char> >::basic_ifstream(const std::basic_ifstream<char, std::char_traits<char> >&) 123.cpp:6: error: no matching function for call to 'std::basic_ofstream<char, std::char_traits<char> >::basic_ofstream(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)' /usr/include/c++/4.4/fstream:623: note: candidates are: std::basic_ofstream<_CharT, _Traits>::basic_ofstream(const char*, std::_Ios_Openmode) [with _CharT = char, _Traits = std::char_traits<char>] /usr/include/c++/4.4/fstream:608: note: std::basic_ofstream<_CharT, _Traits>::basic_ofstream() [with _CharT = char, _Traits = std::char_traits<char>] /usr/include/c++/4.4/iosfwd:84: note: std::basic_ofstream<char, std::char_traits<char> >::basic_ofstream(const std::basic_ofstream<char, std::char_traits<char> >&) 123.cpp: In function 'int main()': 123.cpp:23: warning: comparison between signed and unsigned integer expressions