anchor.diff:              use_pointers = .FALSE.
           end if
   
  -        n = size(x, kind=ip) 
  +        n = size(x, kind=ip)
           linear_interpolator%n = n
           if(n /= size(y, kind=ip)) then
               print*, 'initialise_linear_interpolator error: size of x and y must be equal'
  
positive.code:     pure subroutine nearest_index_sorted(n, x, y, output)
          integer(ip), intent(in) :: n
          real(dp), intent(in) :: x(n)
          real(dp), intent(in) :: y      
          integer(ip), intent(out) :: output
  
          integer :: i, upper, lower
  
          if(y < x(1)) then
              output = 1
          else 
              if (y > x(n)) then
                  output = n
              else
  
negative.code:             else
                  print*, 'FAIL', li%xs - x
              end if
  
              if(all(abs(li%ys - y) < 1.0e-10_dp)) then
                  print*, 'PASS'
              else
  