/** Our internal representation of a Paren
 * in the X0 language.
 * See http://www.radford.edu/itec380/2019spring-ibarland/Homeworks/Project/
 * 
 * @author Ian Barland
 * @version 2018.Nov.16
 */

public class Paren extends Expr {

  Expr e;
  static final String START_TOKEN = "[";
  static final String STOP_TOKEN  = "]";

  Paren( Expr _e ) {
    this.e  = _e;
    }
  
  public String toString(/* Paren this */) {
    return START_TOKEN
         + this.e.toString()
         + STOP_TOKEN
         ;
    }
    
  public static Paren parse( java.util.Scanner s, String punctuation ) {
      UtilIan.verifyToken( UtilIan.nextSplittingBy(s,punctuation), START_TOKEN); // Consume the opening "[", and continue.
      
      // NOTE: recur with `Expr.parse` -- not `parse` = `Paren.parse` which is NOT what we want!
      Expr theInsideExpr = Expr.parse(s,punctuation);
      
      UtilIan.verifyToken( UtilIan.nextSplittingBy(s,punctuation), STOP_TOKEN);   // Consume the closing "]", and continue. 
      return new Paren(theInsideExpr);
      }
      
      
      
  public Value eval() {
    return this.e.eval();
    }
    
    
  @Override
  public boolean equals( /* Paren this, */ Object that) {
    if (this==that) {
      return true;
      }
   else if (that==null) {
      return false;
      }
   else if (this.getClass() != that.getClass()) {
      return false;
      }
   else {
      Paren thatt = (Paren) that;
      return this.e.equals(thatt.e);
      }
    
    }
    
  @Override
  public int hashCode() {
    if (cachedHash == null) {
      int hashSoFar = 0;
      hashSoFar *= 0b11111;
      hashSoFar += this.e.hashCode();
      cachedHash = hashSoFar;
      }
    return cachedHash;
    }
  private Integer cachedHash = null;
 
  }