evalLip :: Frac MPBall -> MPBall -> MPBall -> MPBall -> MPBall
evalLip f@(Frac _ _ m) lp lq x =
  fc + (hullMPBall (-errB) (errB))
  where
  absFc = abs fc
  fc    = evalDirect f c
  c     = centreAsBall x
  eps   = mpBall $ radius x
  errB  = m*(lp + lq*absFc)*eps
evalLip :: Frac MPBall -> MPBall -> MPBall -> MPBall -> MPBall
evalLip f@(Frac _ _ m) lp lq x =
  fc + (hullMPBall (-errB) (errB))
  where
  absFc = abs fc
  fc    = evalDirect f c
  c     = centreAsBall x
  eps   = mpBall $ radius x
  errB  = m*(lp + lq*absFc)*eps
evalLip f@(Frac _ _ m) lp lq x =
  fc + (hullMPBall (-errB) (errB))
  where
  absFc = abs fc
  fc    = evalDirect f c
  c     = centreAsBall x
  eps   = mpBall $ radius x
  errB  = m*(lp + lq*absFc)*eps