//code
inputfrac.erase(std::remove_if(inputfrac.begin(), inputfrac.end(), std::isspace), inputfrac.end());


//compiler
error: no matching function for call to ‘remove_if(__gnu_cxx::__normal_iterator<char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, __gnu_cxx::__normal_iterator<char*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, <unresolved overloaded function type>)’