anchor.diff:  SUBROUTINE constants(K0, K1, K2, Kb, Kw, Ks, Kf, Kspc, Kspa,  &
                        K1p, K2p, K3p, Ksi,                      &
                        St, Ft, Bt,                              &
  -                     temp, sal,                               &
  +                     temp, sal, Patm,                         &
                        depth, lat, N,                           &
                        optT, optP, optB, optK1K2, optKf)
   
  
positive.code:   REAL(kind=r8) :: t, tk, prb
    REAL(kind=r8) :: s, sqrts, s15, scl
  
  ! Arrays to pass optional arguments into or use defaults (Dickson et al., 2007)
    CHARACTER(3) :: opB
    CHARACTER(2) :: opKf
  
negative.code:         invtk=1.0d0/tk
          dlogtk=LOG(tk)
  
  !       Atmospheric pressure
          Patmd = DBLE(Patm(i))
  
  !       Hydrostatic pressure (prb is in bars)
          prb = DBLE(p) / 10.0d0
  
  !       Salinity and simply related values
  