1 computePi :: Double -> Double
  2 computePi n = help n 0.0
  3     where help n pi | n <  0 = pi
  4                     | n >= 0 = help (n-1) (pi + ((1/16.0**n)*(
  5                                                                4/(8*n+1)
  6                                                                -2/(8*n+4)
  7                                                                -1/(8*n+5)
  8                                                                -1/(8*n+6))))