[jhenry7@hills ~]$ g++ mywc.cpp -o mywc
mywc.cpp: In function ‘int num_lines(std::string)’:
mywc.cpp:36:23: error: no matching function for call to ‘std::basic_ifstream<char>::basic_ifstream(std::string&)’
  ifstream ifs(filename);
                       ^
mywc.cpp:36:23: note: candidates are:
In file included from mywc.cpp:9:0:
/opt/gcc4.9.1/include/c++/4.9.1/fstream:470:7: note: std::basic_ifstream<_CharT, _Traits>::basic_ifstream(const char*, std::ios_base::openmode) [with _CharT = char; _Traits = std::char_traits<char>; std::ios_base::openmode = std::_Ios_Openmode]
       basic_ifstream(const char* __s, ios_base::openmode __mode = ios_base::in)
       ^
/opt/gcc4.9.1/include/c++/4.9.1/fstream:470:7: note:   no known conversion for argument 1 from ‘std::string {aka std::basic_string<char>}’ to ‘const char*’
/opt/gcc4.9.1/include/c++/4.9.1/fstream:456:7: note: std::basic_ifstream<_CharT, _Traits>::basic_ifstream() [with _CharT = char; _Traits = std::char_traits<char>]
       basic_ifstream() : __istream_type(), _M_filebuf()
       ^
/opt/gcc4.9.1/include/c++/4.9.1/fstream:456:7: note:   candidate expects 0 arguments, 1 provided
/opt/gcc4.9.1/include/c++/4.9.1/fstream:430:11: note: std::basic_ifstream<char>::basic_ifstream(const std::basic_ifstream<char>&)
     class basic_ifstream : public basic_istream<_CharT, _Traits>
           ^
/opt/gcc4.9.1/include/c++/4.9.1/fstream:430:11: note:   no known conversion for argument 1 from ‘std::string {aka std::basic_string<char>}’ to ‘const std::basic_ifstream<char>&’
mywc.cpp:39:26: error: ‘line’ was not declared in this scope
       while (getline(ifs,line))

the code that works is

int main(int argc,char **argv)
   {
   argcheck(argc);
   string line;
   ifstream ifs(argv[1]);
   int num_l(0);
   if (ifs.is_open())
   {
      while (getline(ifs,line))
      {
         cout << line << ++num_l << endl;
      }
   }
   else
   {
      die("Unable to open");
      ifs.close();
   }
   return (0);
   }



i want to put the action here into a function,