  Exercise 2.7 :  ’s program is incomplete because she has not specified the implementation of the interval abstraction . Here is a definition of the interval constructor :

; (define (make-interval a b) (cons a b))
; Define selectors upper-bound and lower-bound to complete the implementation.
#lang planet neil/sicp

(define (make_interval a b) (cons a b))
(define (upper_bound x) (car x))
(define (lower_bound x) (cdr x))

(define a 
    (make_interval 1 2)
)
(upper_bound a)
(lower_bound a)
````````````````````````````````````````
Welcome to DrRacket, version 6.6 [3m].
  memory limit : 128 MB .
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> 
 (define (make-interval a b) (cons a b))
 Define selectors upper-bound and lower-bound to complete the implementation.
  Exercise 2.7 :  ’s program is incomplete because she has not specified the implementation of the interval abstraction . Here is a definition of the interval constructor :

#lang planet neil/sicp

(define (make_interval a b) (cons a b))
(define (upper_bound x) (car x))
(define (lower_bound x) (cdr x))

(define a 
    (make_interval 1 2)
)
(upper_bound a)
(lower_bound a)
````````````````````````````````````````
Welcome to DrRacket, version 6.6 [3m].
  memory limit : 128 MB .
1
2
> 