杨辉三角---scheme表示

(define (pr n)
  (define (update l)
    (if (not (null? (cdr l)))
        (begin
          (set-car! l (+ (car l) (car (cdr l))))
          (update (cdr l)))))
  (let t ((l '(1)) (i 1))
    (if (<= i n)
        (begin
          (display l) (newline)
          (update l)
          (t (cons 1 l) (+ 1 i))))))

(pr 12)

(1)
(1 1)
(1 2 1)
(1 3 3 1)
(1 4 6 4 1)
(1 5 10 10 5 1)
(1 6 15 20 15 6 1)
(1 7 21 35 35 21 7 1)
(1 8 28 56 70 56 28 8 1)
(1 9 36 84 126 126 84 36 9 1)
(1 10 45 120 210 252 210 120 45 10 1)
(1 11 55 165 330 462 462 330 165 55 11 1)