!
!       project "gravity field"
!
!-----------------------------------------------------------------------
module realfield
  implicit none

!-----------------------------------------------------------------------

type massbody
  real                  :: posx, posy
  real                  :: mass
  integer               :: serial
end type

!-----------------------------------------------------------------------
contains

function compute_gravity(ix, iy, body)

  integer, intent(in)           :: ix, iy
  type(massbody), intent(in)    :: body
  real                          :: compute_gravity
  real                           :: rx, ry, dist

  rx = real(ix) - body%posx
  ry = real(iy) - body%posy

  dist = sqrt( (rx*rx) + (ry*ry) )
  if (dist .LT. 0.15) then
    write (0, *) "dist too small ", dist
    compute_gravity = 0e0
  endif

  compute_gravity = body%mass * (dist ** 2)

end function

!-----------------------------------------------------------------------
!-----------------------------------------------------------------------

end module