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package ilog.language.design.types;

/**
 * @version     Last modified on Mon Oct 07 09:45:54 2002 by hak
 * @author      <a href="mailto:hak@ilog.fr">Hassan A&iuml;t-Kaci</a>
 * @copyright   &copy; 2000-2002 <a href="http://www.ilog.fr/">ILOG, S.A.</a>
 */

import java.util.Iterator;

import ilog.language.util.Locatable;
import ilog.language.design.kernel.Global;

public class PruningGoal extends Goal
{
  /**
   * The global being pruned.
   */
  private Global _global;

  /**
   * The type filter.
   */
  private Type _filter;

  /**
   * The locatable extent.
   */
  private Locatable _extent;

  public PruningGoal (Global global, Type filter, Locatable extent)
    {
      _global = global;
      _filter = filter;
      _extent = extent;
    }

  /**
   * Returns this pruning goal's global.
   */
  final Global global ()
    {
      return _global;
    }

  /**
   * Returns this pruning goal's (undereferenced) filter.
   */
  final Type filter ()
    {
      return _filter;
    }

  final Locatable extent ()
    {
      return _extent;
    }

  final void prove (TypeChecker typeChecker) throws FailedUnificationException
    {
      trail(typeChecker);
      _global.filter().unify(_filter,typeChecker);
    }

  /**
   * Returns a string form of this typing goal.
   */
  final public String toString ()
    {
      return super.toString() +
             ": (pruning) global => " + _global +
             ", filter => " + _filter.value();
    }
}