PostScript Quadtree Grammars

/quadtree {
    2 dict begin

    /size exch def
    /half size 2 div def

    size 1 eq {
        0 setgray
        size size rect
    } {
        half quadtree

        gsave
        0 half translate
        1 setgray
        half half rect
        grestore

        gsave
        half 0 translate
        half quadtree
        grestore

        gsave
        half half translate
        half quadtree
        grestore
    } ifelse
    end
} def

1024 quadtree
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