// Ian! D. Allen - idallen@idallen.ca - www.idallen.com
// FunnyMath4 - wrong answers from simple arithmetic

// Compile and run this program.
// Explain why some of the outputs are incorrect.

public class FunnyMath4 {
    public static void main(String[] args) {
        int n = 25;
        double x;
        System.out.println("Add up increasing numbers of tenths");
        System.out.printf("%2s %3s %3s %20s %20s\n",
		"i", "10i", "cou", "xprev", "x");
        System.out.printf("%2s %3s %3s %20s %20s\n",
		"--", "---", "---", "-------------------", "-------------------");
        for (int i = 0; i < n; i++) {
           int counter = 0;
           double xprevious = 0.0;
           for (x = 0.0; x < i; x += 0.1) {
              counter++;
              xprevious = x;
           }
           System.out.printf("%2d %3d %3d %20.17f %20.17f",
		   i,  (10*i), counter, xprevious, x );
           // we should have looped 10*i times to increment counter
           if ( 10*i != counter ) {
              System.out.print("  *** ERROR ***" );
           }
           System.out.println("");
        }
    }
}

/*
OUTPUT

Add up increasing numbers of tenths
 i 10i cou                xprev                    x
-- --- ---  -------------------  -------------------
 0   0   0  0.00000000000000000  0.00000000000000000
 1  10  11  0.99999999999999990  1.09999999999999990  *** ERROR ***
 2  20  20  1.90000000000000060  2.00000000000000040
 3  30  30  2.90000000000000120  3.00000000000000130
 4  40  40  3.90000000000000200  4.00000000000000200
 5  50  51  4.99999999999999800  5.09999999999999800  *** ERROR ***
 6  60  61  5.99999999999999500  6.09999999999999400  *** ERROR ***
 7  70  71  6.99999999999999100  7.09999999999999100  *** ERROR ***
 8  80  81  7.99999999999998800  8.09999999999998700  *** ERROR ***
 9  90  91  8.99999999999998400  9.09999999999998400  *** ERROR ***
10 100 101  9.99999999999998000 10.09999999999998000  *** ERROR ***
11 110 111 10.99999999999997700 11.09999999999997700  *** ERROR ***
12 120 121 11.99999999999997300 12.09999999999997300  *** ERROR ***
13 130 131 12.99999999999997000 13.09999999999997000  *** ERROR ***
14 140 141 13.99999999999996600 14.09999999999996600  *** ERROR ***
15 150 151 14.99999999999996300 15.09999999999996200  *** ERROR ***
16 160 161 15.99999999999996000 16.09999999999996000  *** ERROR ***
17 170 171 16.99999999999997000 17.09999999999997300  *** ERROR ***
18 180 181 17.99999999999998600 18.09999999999998700  *** ERROR ***
19 190 190 18.90000000000000000 19.00000000000000000
20 200 200 19.90000000000001300 20.00000000000001400
21 210 210 20.90000000000002700 21.00000000000003000
22 220 220 21.90000000000004000 22.00000000000004300
23 230 230 22.90000000000005500 23.00000000000005700
24 240 240 23.90000000000007000 24.00000000000007000
*/