实现简单的输入流

readline

struct mystream : istreamByReadLine {
  istream& s;
  mystream(istream& _s):s(_s){}
  virtual string getline() {
    string line;
    getline(s,line);
    f(line);
    return line;
  }
}

class istreamByReadLine : istream {
  ... // implementing everything needed to be istream compatible, using my
  ... // getline() virtual method
}

Line

>>

Line line
while ( source >> line ) ...

operator std::string() const

std::istream& operator>>( std::istream&, Line& dest )

streambuf