private void DiscardToken()
{
_previousToken = _currentToken.Clone();
_currentToken = _nextToken.Clone();
_nextToken = _tokenSequence.Any() ?
_tokenSequence.Dequeue() : new RuleToken(Lexicon.SequenceTerminator, string.Empty);
}
private void SetupPointerTokens()
{
_previousToken = null;
_currentToken = _tokenSequence.Dequeue();
_nextToken = _tokenSequence.Dequeue();
}