new euler

data Euler =
  Euler { x     :: Double
        , y     :: Double
        , deriv :: (Double -> Double -> Double)
        , delta :: Double
        , end   :: Double }
 
euler :: Euler -> Double
euler e
  | x e == end e = y e
  | otherwise    = euler Euler { x = (x e + (delta e)), y = ((deriv e) (x e) (y e)), deriv = (deriv e), delta = (delta e), end = end e}