code: private final boolean lookbehind(char c, int n)
    {
  
      boolean isToken;
      int lookBehindPos = m_queueMark - (n + 1);
  
      if (lookBehindPos >= 0)
      {
        String lookbehind = (String) m_ops.m_tokenQueue.elementAt(lookBehindPos);
  
        if (lookbehind.length() == 1)
        {
          char c0 = (lookbehind == null) ? '|' : lookbehind.charAt(0);
  
          isToken = (c0 == '|') ? false : (c0 == c);
        }
        else
        {
          isToken = false;
        }
      }
      else
      {
        isToken = false;
      }
  
      return isToken;
    }
docs: Look behind the first character of the current token in order to
  make a branching decision.
  
  @param c the character to compare it to.
  @param n number of tokens to look behind.  Must be
  greater than 1.  Note that the look behind terminates
  at either the beginning of the string or on a '|'
  character.  Because of this, this method should only
  be used for pattern matching.
  
  @return true if the token behind the current token matches the character
  argument.