anchor.diff:  	0 dsp x8 sd,
   	next,
   tend-code
  -t: I	R@ ;
   
   \ SP@ and SP! retrieve and reset the data stack pointer.
   \ BE EXTREMELY CAREFUL WHEN USING SP!, AS THIS CAN LEAD
  
positive.code: \ Dr. C. H. Ting and Juergen Pintaske, as of 2013-Apr-20.
  \ See http://www.exemark.com/FORTH/eForthOverviewv5.pdf
  
  
  \ ?branch causes a control flow change if the TOS is zero.
  \ This primitive consumes the stack item.
  
negative.code: \ TODO test
  : ~AGAIN	[t'] branch t, t, ;
  : ~UNTIL	[t'] ?branch t, t, ;
  : ~FOR		[t'] (dofor) t, there ;
  : ~NEXT		[t'] ?next t, t, ;
  
  \ PANIC will stop all program execution until the machine
  \ is physically reset.  This includes interrupt handlers.
  