class ArraySet {
    private static Object[] a;
    public  static int size;

    /*:
      public static ghost specvar init :: bool;

      public static specvar content :: objset;
      vardefs
        "content == {n. EX j. n = a.[j] & 0 <= j & j < size}";

      invariant "init --> a ~= null & 0 < a..Array.length & 
          0 <= size & size <= a..Array.length";

    */

    public static void initialize() 
    /*:
      modifies init, content
      ensures "init & content = {}";
    */
    {
        a = new /*: hidden */ Object[100];
        size = 0;
        //: init := "True";
    }


    public static boolean contains(Object x)
    /*:
      requires "init & x ~= null"
      ensures "result = (x : content)";
     */
    {
	/*: private static ghost specvar content_i :: objset;

	 private specvar bounds :: bool;
	 private vardefs "bounds == 0 <= i & i <= size";

	 private specvar a_i :: obj;
	 private vardefs "a_i == a.[i]";

       */
        int i = 0;
        //: content_i := "{}";
        while /*: inv "0 <= i & i <= size &
                 (content_i = {n. EX j. n = a.[j] & 0 <= j & j < i }) &
                 (x ~: content_i)" */
            (i < size) {
            if (a[i] == x) {
                return true;
            } else {
                //: content_i := "content_i Un {a.[i]}";
                i = i + 1;
            }
        }
        return false;
    }

    public static void driver()
    {
	int i = 0;
	int n = 10;
	boolean b0;
	boolean b1;
	Object j; 
	
	initialize();
	
	while (i < n)
	{
	    j = new Object ();
	    add(j);
	    i = i + 1;
	}
	Object k = new Object ();

	b0 = containsVC(j);
	b1 = containsVC(k);

	//: assert "b0";
	//: assert "~b1";
    }
}