연습문제 4.4

<blockquote>(define (eval-and exp env)
  (if (null? exp)
      #t
      (let ((test (car exp)))
        (if (eval test)
            (eval-and (cdr exp) env)
            #f))))

(define (eval-or exp env)
  (if (null? exp)
      #f
      (let ((test (car exp)))
        (if (eval test)
            #t
            (eval-or (cdr exp) env)))))

(define (and? exp)
  (tagged-list? exp 'and))

(define (or? exp)
  (tagged-list? exp 'or))
</blockquote>

좀 아리까리함..