anchor.diff:               interval_b = midpoint
             END IF
             !! Check convergence.
  -          IF ( ABS(zero_value-0.5_NTREAL) .LT. solver_parameters%converge_diff ) THEN
  +          IF (ABS(zero_value-0.5_NTREAL) .LT. &
  +               & solver_parameters%converge_diff) THEN
                EXIT
             END IF
          END DO midpoints
  
positive.code:                 zero_value = zero_value*zero_value
               ELSE
                  tempfx = (zero_value*zero_value) &
                           & * (4.0_NTREAL*zero_value - 3.0_NTREAL*zero_value*zero_value)
                  tempgx = (zero_value*zero_value) * (1.0_NTREAL-zero_value) &
                           & * (0.0_NTREAL-zero_value)
                  zero_value = tempfx + sigma_array(inner_counter)*tempgx
               END IF
            END DO polynomial
  
negative.code:           zero_value = midpoint
            !! Compute polynomial function at the guess point.
            polynomial:DO inner_counter=1,total_iterations
               zero_value = zero_value + &
                    & 2.0_NTREAL*((zero_value**2)*(1.0_NTREAL-zero_value) &
                    & - sigma_array(inner_counter)* &
                    & zero_value*(1.0_NTREAL-zero_value))
            END DO polynomial
            !! Change bracketing.
            IF (zero_value .LT. 0.5_NTREAL) THEN
  