program Chop
/******************************************************************************
 * Description:  This program uses the fact that numbers in the toy machine are 
 *               represented by 16-bit signed two's complement numbers.  
 *               To learn more about signed two's complement numbers, please 
 *               see Professor Wayne's notes on the TOY machine.  
 *               Note: a non-positive value of N will cause undefined behavior.
 * Input:        N  
 * Output:       The unique set of powers of 2 which sum to N
 ******************************************************************************/

// Initialize
10: 82FF   read R[2]                     

// Check for non-positive values
11: D213   if (R[2] > 0) goto 13         
12: 0000   halt                          

// Loop
13: 2302   R[3] <- -R[2]                 
14: 3423   R[4] <- R[2] & R[3]           
15: 94FF   write R[4]                    
16: 2224   R[2] <- R[2] - R[4]           
17: D211   if (R[2] > 0) goto 11         

18: 0000   halt