# Main Command: Go
# Blancmange Curve by Guy Walker
# www.logoarts.co.uk

to new
  # set default screen, pen and turtle 
  ResetAll SetScreenSize [400 400] HideTurtle 
  SetSC Black SetPC Green SetPS 1 PenUp 
end

to init
  # create empty list
  Make "Y [ ]
  Repeat 257 [ Make "Y LPut 0 :Y ]
end

to display
  # write header title
  SetPC White PenUp 
  SetPos [-190 180] Label [Blancmange Curve]
end

to blancmange
  # calculate heights
  Make "Index 256
  For [N 1 8] [
    For (List "M 1 256 :Index) [
      Make "Average ((Item :M :Y) + Item (:M + :Index ) :Y) / 2
      Make "Y SetItem :Y (:M+:Index/2) (:Index + :Average) ]
    Make "Index :Index / 2 ]
end

to draw
  # draw curves from list
  Make "Index 256
  For [N 1 8] [ 
    Wash Display 
    PenUp SetPos [-127 -100] PenDown SetPC Pink 
    For (List "P 1 257 :Index) [SetPos List :P-128 (Item :P :Y) / 2 -100] 
    Make "Index :Index / 2 Wait 80]
end

to go
  New Init
  Blancmange Draw
end