anchor.diff:  
       integer :: L
       integer :: R
  +    integer :: n_iteration
       real(8) :: testval
   
       L = 1
  
positive.code:        elseif (val < testval) then
            R = array_index
         end if
      end do
  
      array_index = L
  
negative.code:        call fatal_error()
      end if
      
      n_iteration = 0
      do while (R - L > 1)
         
         ! Check boundaries
  