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using Ilog.Language.Util;
using Ilog.Language.Tools;

namespace Ilog.Language.Parsing
{
  using Stack = Util.Stack;
  using IList = System.Collections.IList;
      
  /**
   * This implements the type of choice points pushed on the choice
   * stack by a dynamic parser.
   *
   * @see         DynamicParser
   *
   * @version     Last modified on Sun May 29 09:18:03 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 Choice : TimeStamped
    {
      /**
       * Constructs an empty choice point.
       */
      internal Choice ()
        {
	  options = new Stack(2);
	}

      /**
       * Constructs an empty choice point with the specified
       * option stack size.
       */
      internal Choice (int size)
        {
	  options = new Stack(size);
	}

      /**
       * Constructs a choice point with the specified option stack.
       */
      internal Choice (Stack options)
        {
	  this.options = options;
	}

      /**
       * This choice point's time stamp.
       */
      private long stamp;
      public long TimeStamp
        {
	  get { return stamp; }
	  set { stamp = value; }
	}

      /**
       * This is true iff this choice point is among dynamic tokens.
       * This is true by default.
       */
      private bool isTokenChoice = true;
      internal bool IsTokenChoice
        {
	  get { return isTokenChoice; }
	  set { isTokenChoice = value; }
	}

      /**
       * This choice point's option stack.
       */
      private Stack options;
      internal Stack Options
        {
	  get { return options; }
	}

      /**
       * This is true iff there no options left for this choice point.
       */
      internal bool IsEmpty
        {
	  get { return options.Count == 0; }
	}

      /**
       * Adds the specified object as an option for this choice point.
       */
      internal void AddOption (object elt)
        {
	  options.Push(elt);
	}

      /**
       * Adds the specified list of objects as options for this choice
       * point.       
       */
      internal void AddOptions (Stack stack)
        {
	  foreach (object elt in stack)
	    options.Push(elt);
	}

      /**
       * Returns a string description of this choice point.
       */
      public override string ToString ()
        {
	  return Misc.View(options,"(stamp:"+TimeStamp+") ",18,64);
	}
    }
}