# given a line and a cursor position returns the word
# under the cursor. Takes only spaces into account, not punctuation
# characters.
    def _get_word_under_cursor line, pos
      finish = line.index(" ", pos)
      start = line.rindex(" ",pos)
      finish = -1 if finish.nil?
      start = 0 if start.nil?
      return line[start..finish]
    end