anchor.diff:      if (allocated(nk)) then
          if (alphabet_size > n_bins) then
             unobserved = alphabet_size - n_bins*1.0_float64
  -          if (minval(nk) < 1.e-3_float64) then
  +          if (minval(nk) ==  0) then
                k = minloc(nk, 1)
                zk(k) = zk(k) + unobserved
             else
  
positive.code:   implicit none
  
    integer, intent(in)  :: n
    real(float64), intent(in)    :: nk1(n)
    real(float64), intent(in)    :: zk1(n)
    real(float64), intent(in)    :: nc
    real(float64),   intent(in)  :: alpha
    real(float64),   intent(out) :: estimate
  
negative.code:   implicit none
  
    integer, intent(in)  :: n
    integer, intent(in)    :: nk1(n)
    integer, intent(in)    :: zk1(n)
    real(float64), intent(in)    :: nc
    real(float64),   intent(out) :: estimate
    real(float64),   intent(out) :: err_estimate
  