/cross { % x y => - (draw cross)
10 dict begin		% define a local dict
    /y exch def		% save the y value
    /x exch def		% save the x value

    % clear the stone:
    x .5 sub y .5 sub 1 1 rectpath		% define a path
    board_color setcolor 		% set color
    fill		% erase stone

    % draw the two cross strokes, carfully adjusting for edge locations:
    x .5 sub 0 max y moveto x .5 add BOARD_MAX min y lineto  % hrz stroke
    x y .5 sub 0 max moveto x y .5 add BOARD_MAX min lineto  % vrt stroke
    line_color setcolor 		% set color
    stroke		% stroke cross
    pause		% allow other processes 
		%  to execute
end		% end dict
} def