// BitQuiz.java
// David Kosbie, 15-111/AB, Spring 2007

/*
Standard disclaimer:  As usual with sample code designed (often in
class!) to demonstrate specific issues, the style may not be perfect
(it is especially lacking comments and top-down design), and there may
even be a bug or two lurking in the code!
*/

import java.util.*;

public class BitQuiz {
   private static Scanner scanner = new Scanner(System.in);
   private static Random random = new Random();
   
   public static int eval(int arg1, String operator, int arg2) {
      if (operator.equals("&"))   return (arg1 & arg2);
      if (operator.equals("|"))   return (arg1 | arg2);
      if (operator.equals("^"))   return (arg1 ^ arg2);
      if (operator.equals("~"))   return (~arg1);
      if (operator.equals("<<"))  return (arg1 << arg2);
      if (operator.equals(">>"))  return (arg1 >> arg2);
      if (operator.equals(">>>")) return (arg1 >>> arg2);
      System.out.printf("Unknown operator: %s\n",operator);
      return 0;
   }
   
   public static void main(String[] args) {
      System.out.println("This program repeatedly generates random");
      System.out.println("bit manipulation problems.  Enter a");
      System.out.println("non-int value to quit the program.\n");
      
      String[] operators = { "&", "|", "^", "~", ">>", ">>>", "<<" };
      // This generates problems in the range [min,max].  Change these
      // values to make the poblems easier or harder
      int min = -8, max = 8;
      while (true) {
         String operator = operators[random.nextInt(operators.length)];
         int arg1 = min + (random.nextInt(max - min + 1));
         int arg2;
         if (operator.length() > 1)
            // it's a shift operator, so keep arg2 small + non-negative
            arg2 = random.nextInt(4);
         else
            arg2 = min + (random.nextInt(max - min + 1));
         if (operator.equals("~"))
            // unary negation has no second arg!
            System.out.printf("~%d = ",arg1);
         else
            System.out.printf("%d %s %d = ",arg1,operator,arg2);
         if (!scanner.hasNextInt()) {
            System.out.println("Goodbye!");
            break;
         }
         int response = scanner.nextInt();
         int result = (byte)eval(arg1,operator,arg2);
         if (response == result)
            System.out.println("Correct!!!\n");
         else
            System.out.printf("Sorry, but the answer is: %d\n\n",
                              result);
      }
   }
}