gistfile1.hs

import Graphics.UI.GLUT 
import Graphics.Rendering.OpenGL 

main = do 
  (name,_) <- getArgsAndInitialize 
  createWindow name
  displayCallback $= display
  mainLoop

display = do
  setup
  currentColor $= Color4 0.35 0.21 1 1 -- bluish
  renderPrimitive Points points
  flush
  where
    gingerbread (x1,y1) = (x1,y1::GLfloat) : gingerbread(1-y1+abs(x1), x1) -- infinite list! (of gingerbread man points)
    iterations          = take 100000 (gingerbread((-0.1), 0)) -- take the first n from our infinite list. laziness!
    points              = mapM_ (\(a,b) -> vertex $ Vertex2 a b) iterations -- monads?! turn the pairs we have into vertex commands we can give to renderPrimitive
    setup = do
      clearColor $= Color4 1 1 1 0.1
      clear [ColorBuffer]
      scale               0.15 0.15 (0.15::GLfloat)
      translate $ Vector3 (-3.1) 0 (0::GLfloat)
      rotate 45 $ Vector3 0 0 ((-45)::GLfloat)

-- renders the "gingerbread man" IFS in haskell with some GL libraries.