/** Our internal representation of a BinOp
 * in the S0 language.
 * See http://www.radford.edu/itec380/2017fall-ibarland/Homeworks/Project/
 * 
 * @author Ian Barland
 * @version 2017.Nov.28
 */
public class BinOp extends Expr {

  Expr left, right;
  String op;
  
  public static final java.util.List<String> OPS = java.util.Arrays.asList( "ad", "su", "mu" );

  BinOp( Expr _left, Expr _right, String _op ) {
    this.left  = _left;
    this.right = _right;
    this.op    = _op;
    }
  
  public String toString( /* BinOp this */) {
    return "?"
         + " "
         + this.op
         +" "
         + this.left.toString()
         + " "
         + this.right.toString()
         ;
      }
    
  public Value eval( /* BinOp this */) {
    String theOp    = this.op;
    double leftVal  = ((Num)(this.left .eval())).doubleValue();
    double rightVal = ((Num)(this.right.eval())).doubleValue();
    if (this.op.equals("ad")) {
      return new Num(leftVal + rightVal);
      }
    else if (this.op.equals("su")) {
      return new Num(leftVal - rightVal);
      }
    else if (this.op.equals("mu")) {
      return new Num(leftVal * rightVal);
      }
    else {
      throw new RuntimeException("BinOp.eval(): unknown binary operator `" + this.op + "`");
      }
    }
  
  @Override
  public boolean equals( /* BinOp this, */ Object that) {
    if (this==that) {
      return true;
      }
   else if (that==null) {
      return false;
      }
   else if (this.getClass() != that.getClass()) {
      return false;
      }
   else {
      BinOp thatt = (BinOp) that;
      return this.left.equals(thatt.left)
          && this.op.equals(thatt.op)
          && this.right.equals(thatt.right);
      }
    
    }
    
  @Override
  public int hashCode() {
    if (cachedHash == null) {
      int hashSoFar = (int)0x314d2ef361bcd159L; // fingerprint
      hashSoFar += this.left.hashCode();
      hashSoFar *= 31;
      hashSoFar += this.op.hashCode();
      hashSoFar *= 31;
      hashSoFar += this.right.hashCode();
      cachedHash = hashSoFar;
      }
    return cachedHash;
    }
  private Integer cachedHash = null;

  
  
  
  }