aUCBLogo Demos and Tests / primes_graph

to primes_graph [size 1000000] [flags IntArray size]
   t=timefine
   imax=1+int sqrt size
   for [i 2 imax 1]
   [   if flags.i==0
      [   for [k i+i size i] ~
         [   flags.k=1
         ]
      ]
   ]
   pr timefine-t
   nr=size-flags
   primecount=FloatArray nr
   j=0
   for [i 1 size]
   [   if flags.i==0
      [   j=j+1
         primecount.j=i
      ]
   ]
   clearScreen
   WindowMode
   setPenSize 0
   PenUp
   setXY -400 -300
   PenDown
   setXY (rSeqFA 0 nr nr)/nr*800-400 primecount/size*600-300
   updateGraph
   zoomscene
end