code: func ReplaceN(filename string, r []Replacer, n int) error {
  	e, err := NewEdit(filename)
  	if err != nil {
  		return err
  	}
  
  	err = e.genReplace(r, n)
  	err2 := e.Close()
  	if err != nil {
  		return err
  	}
  	return err2
  }
docs: // ReplaceN replaces a number of regular expressions mathed in r for the named
  // file.