(* http://en.wikipedia.org/wiki/Kerr-Newman_metric *)
include Deriv;;
open Deriv;;
let kn bM bQ bJ =
let bSI = lc 2.99792458e8, (* Speed of Light *)
   lc 6.67384e-11, (* Gravitational Constant *)
   lc 8.9875517873681764e9 (* Coulomb's Constant *)
and gu = lc 1., lc 1., lc 1. in
let c, bG, ke = if 0<1 then gu else bSI (* choice of units *) in
let sq x = x * x and a = bJ / (bM * c) in
let rs = lc 2. * bG * bM / sq c
and rQ2 = sq bQ * bG * ke / sq (sq c) in
fun r th dt dr dth dp ->
  let r2 = sq r and a2 = sq a and sth2 = sq (Sin th) in
  let del = r2 - rs * r + a2 + rQ2
  and rh2 = r2 + a2 * (lc 1. - sth2) in (
  sq (c * dt - a * sth2 * dp) * (del / rh2)
  - (sq dr / del + sq dth) * rh2
  - sq ((r2 + a2) * dp - a * c * dt) * sth2 / rh2) / sq c
in Printf.printf "Boo\n"