Added module interface for orbel_xv2el in anticipation of incorporati…

…ng it into the Python code

src/modules/swiftest_classes.f90

@@ -775,6 +775,19 @@ module pure subroutine orbel_xv2aqt(mu, x, v, a, q, capm, tperi)
          real(DP),               intent(out) :: tperi !! time of pericenter passage
       end subroutine orbel_xv2aqt
 
+      module pure subroutine orbel_xv2el(mu, x, v, a, e, inc, capom, omega, capm)
+         implicit none
+         real(DP),               intent(in)  :: mu    !! Gravitational constant
+         real(DP), dimension(:), intent(in)  :: x     !! Position vector
+         real(DP), dimension(:), intent(in)  :: v     !! Velocity vector
+         real(DP),               intent(out) :: a     !! semimajor axis
+         real(DP),               intent(out) :: e     !! eccentricity
+         real(DP),               intent(out) :: inc   !! inclination
+         real(DP),               intent(out) :: capom !! longitude of ascending node
+         real(DP),               intent(out) :: omega !! argument of periapsis
+         real(DP),               intent(out) :: capm  !! mean anomaly
+      end subroutine orbel_xv2el
+
       module subroutine orbel_xv2el_vec(self, cb)
          implicit none
          class(swiftest_body), intent(inout) :: self !! Swiftest body object

src/orbel/orbel.f90

@@ -890,7 +890,7 @@ module subroutine orbel_xv2el_vec(self, cb)
       end do
    end subroutine orbel_xv2el_vec 
 
-   pure subroutine orbel_xv2el(mu, x, v, a, e, inc, capom, omega, capm)
+   module pure subroutine orbel_xv2el(mu, x, v, a, e, inc, capom, omega, capm)
       !! author: David A. Minton
       !!
       !! Compute osculating orbital elements from relative Cartesian position and velocity
@@ -906,9 +906,17 @@ pure subroutine orbel_xv2el(mu, x, v, a, e, inc, capom, omega, capm)
       !! Adapted from David E. Kaufmann's Swifter routine: orbel_xv2el.f90
       !! Adapted from Martin Duncan's Swift routine orbel_xv2el.f
       implicit none
-      real(DP), intent(in)  :: mu
-      real(DP), dimension(:), intent(in)  :: x, v
-      real(DP), intent(out) :: a, e, inc, capom, omega, capm
+      ! Arguments
+      real(DP),               intent(in)  :: mu    !! Gravitational constant
+      real(DP), dimension(:), intent(in)  :: x     !! Position vector
+      real(DP), dimension(:), intent(in)  :: v     !! Velocity vector
+      real(DP),               intent(out) :: a     !! semimajor axis
+      real(DP),               intent(out) :: e     !! eccentricity
+      real(DP),               intent(out) :: inc   !! inclination
+      real(DP),               intent(out) :: capom !! longitude of ascending node
+      real(DP),               intent(out) :: omega !! argument of periapsis
+      real(DP),               intent(out) :: capm  !! mean anomaly
+      ! Internals
       integer(I4B) :: iorbit_type
       real(DP)   :: r, v2, h2, h, rdotv, energy, fac, u, w, cw, sw, face, cape, tmpf, capf
       real(DP), dimension(NDIM) :: hvec

src/python/orbel.f90

@@ -0,0 +1,32 @@
+module orbel
+    use swiftest
+    private
+    public :: xv2el
+contains
+    pure elemental subroutine xv2el(mu, px, py, pz, vx, vy, vz, a, e, inc, capom, omega, capm)
+        use module_interfaces, only : orbel_xv2el
+        implicit none
+        ! Arguments
+        real*8, intent(in) :: mu, px, py, pz, vx, vy, vz
+        real*8, intent(out) :: a, e, inc, capom, omega, capm
+        !$f2py intent(in) mu
+        !$f2py intent(in) px
+        !$f2py intent(in) py
+        !$f2py intent(in) pz
+        !$f2py intent(in) vx
+        !$f2py intent(in) vy
+        !$f2py intent(in) vz
+        !$f2py intent(out) a
+        !$f2py intent(out) e
+        !$f2py intent(out) inc
+        !$f2py intent(out) capom
+        !$f2py intent(out) omega
+        !$f2py intent(out) capm
+        ! Internals
+        real*8, dimension(3) :: x, v
+        x = [px, py, pz]
+        v = [vx, vy, vz]
+        call orbel_xv2el(x, v, mu, a, e, inc, capom, omega, capm)
+        return
+    end subroutine xv2el
+end module orbel