#lang racket
; exercise 2.7
(define (make-interval a b) (cons a b))
(define (upper-bound interval) (max (car interval) (cdr interval)))
(define (lower-bound interval) (min (car interval) (cdr interval)))
; exercise 2.8
(define (sub-interval x y)
(make-interval
(- (lower-bound x) (upper-bound y))
(- (upper-bound x) (lower-bound y))))
; exercise 2.10
(define (div-interval x y)
(if (<= (* (lower-bound y) (upper-bound y)) 0)
-1(mul-interval x
(make-interval (/ 1.0 (upper-bound y))
(/ 1.0 (lower-bound y))))))
(define (mul-interval x y)
(let ((p1 (* (lower-bound x) (lower-bound y)))
(p2 (* (lower-bound x) (upper-bound y)))
(p3 (* (upper-bound x) (lower-bound y)))
(p4 (* (upper-bound x) (upper-bound y))))
(make-interval (min p1 p2 p3 p4)
(max p1 p2 p3 p4))))
; exercise 2.12
(define (make-center-percent c p)
(make-interval (* c (- 1. p))
(* c (+ 1. p))))
(define (percent interval)
(let ((a (upper-bound interval))
(b (lower-bound interval)))
(/ (- a b) (+ a b))))
(define (center interval)
(/ (+ (lower-bound interval) (upper-bound interval)) 2))
; exercise 2.15
;; 正確
SICP習題解答1 1 1 8
lang racket exercise 1.1 10 5 3 4 9 1 6 2 2 4 4 6 define a 3 define b a 1 a b a b a b if and b a b a b ba cond a 4 6 b 4 6 7 a else 25 2 if b a b a co...
SICP習題解答2 17 2 23
lang racket exercise 2.17 define last pair l cond null?l null null?cdr l l else last pair cdr l last pair list 23 72 149 34 last pair 1 last pair exer...
SICP習題1 6的解答
sicp就是名著 structure and interpretation of computer programs 著名的巫師書 wizard book 和紫書 purple book 雖說英文原版可以從網上合法 中文版翻譯也還不錯。閒話少敘，下面我們研究一下書中 1.1.7節的練習題1.6。原題...