第十三章 用 list 构造表
最后更新于：2022-04-02 04:14:28
[TOC]
## 概述
使用cons构造一个包含多个元素的表十分麻烦,因此 Scheme提供了list操作,这是扩展的 Scheme
语法
` =list`
和扩展的 Scheme值的集合
`=(1ist..,`
理解list表达式的一种简单方法是将它当作若干cons的简写,具体来说,就是将每个形如
`(list exp-1 .. exp-n)`
的表达式看成是如下表达式的简写
`(cons exp-1 (cons ..(cons exp-n empty))`
## 13.1.1
1. (list 0 1 2 3 4 5 )
```
(cons 0
(cons 1
(cons 2
(cons 3
(cons 4
(cons 5 empty))))))
```
2. (list (list 'adam 0) (list 'eve 1) (list 'louisXIV 2))
```
;;(cons x
;; (cons y
;; (cons z empty)))
(cons (cons 'adam (cons 0 empty))
(cons (cons 'eve (cons 1 empty))
(cons (cons 'louisXIV (cons 2 empty)) empty)))
```
3.
```
;;(cons 1
;; (cons x
;; (cons y empty)))
(cons 1
(cons (cons 1 (cons 2 empty))
(cons (cons 1 (cons 2 (cons 3 empty))) empty)))
```
## 13.1.2 const 转 list
1. (cons 'a (cons 'b (cons 'c (cons 'd (cons 'e empty)))))
```
(list 'a 'b 'c 'd 'e)
```
2. (cons (cons 1 (cons 2 empty)) empty)
```
(list (list 1 2))
```
3. (cons 'a (cons (cons 1 empty) (cons false empty)))
```
(list 'a (list 1) false)
```
4. ( cons (cons 1 (cons 2 empty)) (cons (cons 2 (cons 3 empty)) empty))
```
(list (list 1 2 )(list 2 3))
```
## 13.1.3 cons与 list 混合 转 list
1. (cons 'a (list 0 false))
```
(list 'a 0 false)
```
2. (list (cons 1 (cons 13 empty)))
```
(list (list 1 13))
```
3. (list empty empty (cons 1 empty))
```
(list empty empty (list 1 )) ;(list '() '() (list 1))
```
4. (cons 'a (cons (list 1) (list false empty)))
```
(list 'a (list 1) false empty) ; (list 'a (list 1) #false '())
```
## 13.1.4 list 转 list
1. (list (symbol=? 'a 'b) (symbol=? 'c 'c) false)
```
(list false true false)
```
## 13.1.5 list 使用 first 与 rest
1. (first (list 1 2 3))
```
;1
```
2. (rest (list 1 2 3))
```
(list 2 3)
```
## 恢复 list 及 引号
1. '(1 a 2 b 3 c)
```
(list 1 'a 2 'b 3 'c)
```
2. '((alan 1000) (barb 200)(carl 1500) (dawn 2300))
```
(list (list 'alan 1000) (list 'barb 200) (list 'carl 1500) (list 'dawn 2300))
```
3. _
```
'((My Fisrt Paper)
(Sean Fisler)
(Section 1
(Subsection 1 Life is difficult)
(Subsection 2 But learning things makes it interesting))
(Section 2
(Conclustion? What conclustion?)))
//解答
(list
(list 'My 'Fisrt 'Paper)
(list 'Sean 'Fisler)
(list 'Section 1 (list 'Subsection 1 'Life 'is 'difficult) (list 'Subsection 2 'But 'learning 'things 'makes 'it 'interesting))
(list 'Section 2 (list 'Conclustion? 'What 'conclustion?)))
```
';