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namespace Ilog.Language.Parsing
{
  /**
   * This is the type of elements pushed on the dynamic parser's trail
   * stack for undoing reductions and semantic actions effects when
   * backtracking over dynamic operators tokens. It consists of a pair
   * <handle,rule>, where the handle is the sequence of parser stack
   * elements corresponding to the RHS of the rule, which was popped off
   * the parser stack upon reduction using the rule.
   *
   * @see DynamicParser
   *
   * @version     Last modified on Sun May 29 09:26:28 2005 by hak
   * @author      <a href="mailto:hak@ilog.fr">Hassan A&iuml;t-Kaci</a>
   * @copyright   &copy; 2000 <a href="http://www.ilog.fr/">ILOG, S.A.</a>
   */
  internal class TrailEntry : Util.TimeStamped
    {
      /**
       * Constructs a trail entry with the specified handle and rule.
       */
      internal TrailEntry (StackElement[] handle, Rule rule)
        {
	  this.handle = handle;
	  this.rule = rule;
	}

      /**
       * This is the sequence of parser stack elements popped by the
       * reduction using this entry's rule.
       */
      private StackElement[] handle;
      internal StackElement[] Handle
        {
	  get { return handle; }
	}

      /**
       * The reduction rule.
       */
      private Rule rule;
      internal Rule @Rule
        {
	  get { return rule; }
	  set { rule = value; }
	}

      /**
       * The time stamp of this entry. It corresponds to that of the
       * choice point that is in effect at this entry's creation.
       */
      private long stamp;
      public long TimeStamp
        {
	  get { return stamp; }
	  set { stamp = value; }
	}

      /**
       * Returns a string description for this trail entry.
       */
      public override string ToString ()
        {
	  string s = "(stamp:"+stamp+") " + rule.ToString();
	  for (int i=0; i<rule.Length; i++)
	    s += handle[i].Node + " ";
	  return s;
	}
    }
}