///////////  In this class, the instance variable that 
///////////    holds the list of literals that represents
///////////    the state description is assumed to be
///////////    called "literal"


public class PlanningState implements State
{


  
  /**
      Determines whether the state matches all of the
        conditions (literals) in a goal.
      @return true iff all the conditions of the goal are satisfied
   */
  //  Recall that under classical planning assumptions, all
  //    terms in state literals and goal literals are object
  //    constants, so matching can be done without dealing
  //    with substitution or unification.
  
  public boolean isGoal()                                            {
    return goal.size() == literals.countSatisfiedSubgoals(goal);     }
  
  
  /**
       Return an estimator suitable for A*, in the context of
         classical planning.  The estimator is not necessarily 
         optimistic, so it may not lead to the shortest possible
         plan.
    @return the priority of expanding the state
      (lower values give priority over higher values)
   */
  
  public double findEstimate()                                       {
    return 2 * (goal.size() - literals.countSatisfiedSubgoals(goal))
       + history.size();                                             }


}