beta_prime_range_low Subroutine

  subroutine beta_prime_range_low (x)
    implicit none
    real, intent (out) :: x

    do
100    continue
       call tell ('Note: You will be asked to enter:         - d beta/d rho', &
            'Since d beta /d rho <= 0, you should enter a number >= 0')

       call text ('Weakest beta gradient in scan (zero or positive number):')
       read (interactive_input, *, err=100) x
       x = -x
       if (x > 0.) then
          call try_again
       else
          return
       end if
    end do

  end subroutine beta_prime_range_low