/** 
 * CS7 
 * This program plays a simple game with the user.  It asks
 * them for pairs of numbers until they are able to guess
 * the operation correctly.  The main steps are:
 *
 *   while (guess is wrong) {
 *     get input number
 *     calculate real answer
 *     get answer guess
 *     if (incorrect) 
 *       print bad job message
 *   }
 *   print good job message
 */
import tio.*;    // use the package tio 

class GuessOp {
  public static void main (String[] args) {
    double start=0,guess=0,answer=1;  // guess != answer
    
    while (guess != answer) {    // this is false when they win
      System.out.print("Enter an integer: ");
      start = Console.in.readInt();
      answer = start * 2 - 6;    // secret formula, user is trying 
                                 // to infer this based on input/output
      System.out.print("Enter your answer: ");
      guess = Console.in.readInt();

      // tell them they are wrong if they are
      if (guess != answer) 
        System.out.println("Sorry Charlie.  Try it again.");
    }

    // the loop is over, so they found the right number
    System.out.println("Nicely done. " +
        "The formula was f(x) = 2x - 6");

  }
}

/******** SAMPLE OUTPUT:

(9) unixs2 $ java GuessOp
Enter an integer: 3
Enter your answer: 8
Sorry Charlie.  Try it again.
Enter an integer: 5
Enter your answer: 4
Nicely done. The formula was f(x) = 2x - 6
(10) unixs2 $

*********/