A particularly opaque example of density: http://haskell.org/haskellwiki/Euler_problems/11_to_20#Probl...

  problem_18 = head $ foldr1 g tri 
  where
    f x y z = x + max y z
    g xs ys = zipWith3 f xs ys $ tail ys
    tri = [
        [75],
        [95,64],
        [17,47,82],
        ... snip ...