// Returns back an error exception
 private Exception GetErrorException(string p, TokenEntity tokenEntity)
 {
     return new Exception(string.Format("Error at '{0}': {1}", tokenEntity != null ? tokenEntity.StartPos : 0, p));
 }
 private bool AdvanceToken()
 {
     this.lastToken = CurrentToken;
     return this.tokens.MoveNext();
 }