import java.util.Random;

/* An instance of this class models a composite regular expression 
** whose main operator is union (i.e. of the form alpha + beta).
*/
public class RegExprUnion extends RegularExpression {

   // instance variables
   // ------------------

   private RegularExpression alpha, beta;  // This regular expression is 
                                           // alpha + beta

   // constructor
   // -----------

   /* Establishes this regular expression as being the one obtained by
   ** applying the union operator to the given regular expressions.
   */
   public RegExprUnion(RegularExpression first,
                       RegularExpression second) {
      // Stub
   }

   // observer
   // --------

   /* Reports whether or not the given string is a member of the language
   ** represented by this regular expression.
   ** A string x is a member of L(alpha + beta) iff either x is a member of 
   ** L(alpha) or x is a member of L(beta).
   */
   @Override
   public boolean isMember(String x) {
      return true;  // Stub
   }

   @Override
   public boolean isFinite() {
      return true;  // Stub
   }

   @Override
   public boolean isEmpty() {
      return true;  // Stub
   }

   @Override
   public int minLength() {
      return 0;  // Stub
   }

   @Override
   public int maxLength() {
      return 0;  // Stub
   }

   @Override
   public String randomMember(Random rand) {
      if (rand.nextBoolean()) 
         { return alpha.randomMember(rand); }
      else
         { return beta.randomMember(rand); }
   }

   @Override
   public String toString() {
      return '(' + alpha.toString() + 
             ' ' + RegExprSymbols.UNION_OP + ' ' +
             beta.toString() + ')';
   }

   @Override
   public RegularExpression reverse() {
      return null;   // STUB
   }

}