(pretty
   '(println
      (catch
         'found
         (for A (idx 'P)
            (for B (idx 'S)
               (T (<= (car A) (car B)))
               (and
                  (lup S (- (car A) (car B)))
                  (throw
                     'found
                     (conc
                        (cadr (lup S (car B)))
                        (cadr (lup S (- (car A) (car B))))
                        (cdr (lup P (car A))) ) ) ) ) ) ) ) )
(prinl)

Output:

(println
   (catch 'found
      (for A (idx 'P)
         (for B (idx 'S)
            (T (<= (car A) (car B)))
            (and
               (lup S (- (car A) (car B)))
               (throw 'found
                  (conc
                     (cadr (lup S (car B)))
                     (cadr (lup S (- (car A) (car B))))
                     (cdr (lup P (car A))) ) ) ) ) ) ) )
: