ifstream& open_file(ifstream &in, const string &file)
{
in.close();
in.clear();
in.open(file.c_str());
return in;
}
ifstream& open_file(ifstream &in, const sifstream& open_file(ifstream &in, const string &file)
{
in.close();
in.clear();
in.open(file.c_str());
return in;
}
ifstream& open_file(ifstream &in, const s