!+
! Function vec_to_polar (vec, phase) result (polar)
!
! Converts a spin vector to a spin polar
!
! Input:
!   vec(3)   -- real(rp): unitary spin vector
!   phase    -- real(rp), Optional: Phase of the spinor, if not given then
!                                   set to zero
!
! Output:
!   polar    -- spin_polar_struct:
!-

function vec_to_polar (vec, phase) result (polar)

use equal_mod, dummy_except => vec_to_polar

implicit none

type (spin_polar_struct) :: polar

real(rp) vec(3)
real(rp), optional :: phase

!

polar%xi = real_option (0.0d0, phase)
polar%theta = atan2 (sqrt(vec(1)**2 + vec(2)**2), vec(3))
polar%phi = atan2(vec(2), vec(1))
polar%polarization = sqrt(dot_product(vec, vec))

end function vec_to_polar