SICPゼミ第20回

練習問題3.27

練習問題3.28

(define (or-gate a1 a2 output)
  (define (or-action-procedure)
    (let ((new-value (logical-or (get-signal a1) (get-signal a2))))
      (after-delay or-gate-delay (lambda () (set-signal! output new-value)))))
  (add-action! a1 or-action-procedure)
  (add-action! a2 or-action-procedure)
  'ok)

(define (logical-or s1 s2)
  (if (or (= s1 1) (= s2 1)) 1 0))

by pine

練習問題3.29

(define (or-gate2 a1 a2 output)
  (define w1 (make-wire))
  (define w2 (make-wire))
  (define w3 (make-wire))
  (inverter a1 w1)
  (inverter a2 w2)
  (and-gate w1 w2 w3)
  (inverter w3 output))

遅延は(+ and-gate-delay (* inverter-delay 2))
by pine

練習問題3.30

(define (ripple-carry-adder n A B S)
  (define (ripple-carry-adder-iter n m A B S C)
    (let ((c (make-wire)))
      (begin (full-adder (car A) (car B) C (car S) c)
        (+ m 1)
        (if (= n m)
          'done
          (ripple-carry-adder-iter n m (cdr A) (cdr B) (cdr S) c)
          )
        )
      )
    )
  (begin (define c (make-wire)) (half-adder (car A) (car B) (car S) c)
    (ripple-carry-adder-iter n 1 (cdr A) (cdr B) (cdr S) c)
    )
  )