5.1 （1）（I me mine) (2)(is empty) (3) 1234 (4) (23 45) (5) "" (6) () (7) 6 (8) ("" "") (9) 2
5.2
(define (f1 wd1 wd2)
(sentence (bf wd1) (bf wd2)))
(define (f2 wd1 wd2)
(sentence (bf wd1) (bl wd2) (word (first wd1) (last wd2))))
(define (f3 wd1 wd2)
(se wd1 wd1))
(define (f4 wd1 wd2)
(word (first (butfirst wd1)) (first (butfirst wd2))))
5.3 output: m and mezzanine
5.4 output: 4 and square
5.5 output: abc and (a b c)
5.6 輸出一樣
5.7 output: "" and ()
5.8 none
5.9 (matt wright) (brian harvey)
5.10 word returns word sentence returns sentence
5.11 the same as 5.10
5.12
5.13 'banana quote
5.14 (define (third x)
(first(butfirst(butfirst x))))
5.15 (define (first-two x)
(word (first x)(first (butfirst x))))
5.16 (define (two-first x y)
(word (first x)(first y)))
(define (two-first-sent x)
(word (first(first x))(first(first(butfirst x)))))
5.17 (define (knight x)
(se 'Sir x))
5.18 error
5.19 (define (insert-and x)
(se (butlast x) 'and (last x)))
5.20 (define (middle-names x)
(butlast(butfirst x)))
5.21
(define (query x)
(se (first (butfirst x)) (first x) (butfirst(butfirst x)) '?))