anchor.diff:  
           ! Initialise a variable of type kpoint.
           ! In:
  -        !   k (optional): wavevector in units of the reciprocal lattice vectors
  -        !                 of the crystal cell.
  -        !   ms (optional): set spin of an electron occupying the basis function.
  +        !    k (optional): wavevector in units of the reciprocal lattice vectors
  +        !                  of the crystal cell.
  +        !    ms (optional): set spin of an electron occupying the basis function.
           ! Out:
  -        !   kp: initialsed kp.  The wavevector and kinetic energy components are
  -        !       set if the k arguments is given and the ms component is set if
  -        !       the ms argument is given.  If no optional arguments are
  -        !       specified then a completely blank variable is returned.
  +        !    kp: initialsed kp.  The wavevector and kinetic energy components are
  +        !        set if the k arguments is given and the ms component is set if
  +        !        the ms argument is given.  If no optional arguments are
  +        !        specified then a completely blank variable is returned.
           !
           ! This should be called even if k and ms are not specified so that the
           ! k component can be correctly allocated.
  
positive.code:     pure function calc_kinetic(k) result(kinetic)
  
          ! In:
          !   k: wavevector in terms of the reciprocal lattice vectors of the
          !      crystal cell.
          ! Returns:
          !   The kinetic energy associated with a given wavevector.
  
          real(dp) :: kinetic
  
  
negative.code:     pure function is_reciprocal_lattice_vector(k) result(t_rlv)
  
          ! In:
          !    k: wavevector in terms of the reciprocal lattice vectors of the
          !       crystal cell.
          ! Returns:
          !    True if k is a reciprocal lattice vector of the *primitive* cell.
  
          logical :: t_rlv
          integer, intent(in) :: k(ndim)
  