sclass LineBuffer {
  VF1<S> onLine;
  S currentLine = "";
  
  *() {}
  *(VF1<S> *onLine) {}
  
  void append(S s) {
    currentLine += s;
    int i;
    while ((i = currentLine.indexOf('\n')) >= 0) {
      S s = dropTrailingBackslashR(substring(currentLine, 0, i));
      currentLine = substring(currentLine, i+1);
      callF(onLine, s);
    }
  }
}