(define ex1 (cons 1 (cons (cons 2 (cons 3 4)) 5)))
(car ex1) ;=> 1
(cdr ex1) ;=> ((2 . (3 . 4)) . 5)
(car (cdr ex1)) ; => (2 . (3 . 4))
;(car (car ex1)) ;=> error
(car (car (cdr ex1))) ;=> 2
(cdr (cdr ex1)) ; => 5
(cadr ex1) ;=> (car (cdr ex1)) => (2 . (3 . 4))
(caadr ex1) ;=> 2
;(define (make-rat num denom)
; (let ((g (gcd num denom)))
; (cons (/ num g) (/ denom g))))
;(define (numerator rat)
; (car rat))
;(define (denominator rat)
; (cdr rat))
(define (make-rat n d)
(let ((g (gcd n d)))
(lambda (x)(if (= x 0)(/ n g)(/ d g)))))
(define (numerator r)
(r 0)
)
(define (denominator r)
(r 1)
)
(define one-third (make-rat 1 3))
(numerator one-third)
(denominator one-third)
(define (print-rat x)
(display (numerator x))
(display “/”)
(display (denominator x))
(newline))
(define (add-rat r1 r2)
(make-rat (+ (* (numerator r1) (denominator r2))
(* (numerator r2) (denominator r1)))
(* (denominator r1)(denominator r2))))