/SQUARE {
 2 index 2 index moveto  % X Y rmoveto
 0 index 2 div 0 rmoveto % L/2 0 rmoveto
 0 index 2 div 0 exch rmoveto % 0 L/2 rmoveto
 0 index neg 0 rlineto % -L 0 rlineto
 0 index neg 0 exch rlineto % 0 -L rlineto
 0 index 0 rlineto	% +L 0 rlineto
 0 index 0 exch rlineto	% 0 +L rlineto
 clear
 } def

X Y L SQUARE
       			            STACK
       			       3 2 1 0
       			         X Y L

 2 index 			X Y L X
 2 index 2 index		X Y L X Y
 2 index 2 index moveto		X Y L -> X Y moveto

 0 index			X Y L L
 0 index 2 div			X Y L L/2
 0 index 2 div 0	      X Y L L/2 0
 0 index 2 div 0 rmoveto	X Y L -> L/2 0 rmoveto

 0 index 2 div 0	      X Y L L/2 0
 0 index 2 div 0 exch	      X Y L 0 L/2
 0 index 2 div 0 exch rmoveto    X Y L -> 0 L/2 rmoveto

 ..
 0 index neg 0 rlineto		X Y L -> -L 0 rlineto
 ..
 0 index neg 0 exch rlineto	X Y L ->  0 -L rlineto
 ..
 0 index 0 rlineto		X Y L ->  L 0 rlineto
 ..
 0 index 0 exch rlineto		X Y L ->  0 L rlineto
 clear