3.10 数组

8.12

3.10 数组🔗ℹ

azelf内置的数组，取代了racket的list。整体接口偏向Haskell的Data.List。

3.10.1 数组定义🔗ℹ

procedure
(Array? a) → boolean?
a : any/c

是不是数组。

procedure
(Array/c a) → contract?
a : contract?

contract构造器。

syntax
(Array pattern ...)

数组模式匹配关键字。

Examples:

> (define/match1 f
    [(Array) 'empty]
    [(Array _) 'one]
    [(Array _ _) 'two]
    [(Array a b _ ...) (+ a b)]
    [_ 'fucked])
> (f (array))
'empty
> (f (array 1))
'one
> (f (array 1 2))
'two
> (f (array 1 2 3 4))
3

这里需要注意，...匹配出来的数组结构是list，不是Array?。

Example:

> (match (array 1 2 3 4 5)
[(Array xs ...) xs])
'(1 2 3 4 5)

3.10.2 构造新数组🔗ℹ

procedure
(array x ...) → (Array/c a)
x : a

类似list，构造出新的Array?。

Examples:

> (array)
(Array)
> (array 1 2 3)
(Array 1 2 3)

procedure
(list->array xs) → (Array/c a)
xs : (listof a)

list转化成array。

Example:

> (list->array (list 1 2 3))
(Array 1 2 3)

procedure
(repeat n a) → (Array/c a)
n : (or/c zero? positive?)
a : a

Example:

> (repeat 10 "hello")
(Array
"hello"
"hello"
"hello"
"hello"
"hello"
"hello"
"hello"
"hello"
"hello"
"hello")

procedure
(range start end) → (Array/c number?)
start : number?
end : number?

Example:

> (range 1 10)
(Array 1 2 3 4 5 6 7 8 9)

value
empty : (Array/c a)

空数组。

(= (array) empty)

procedure
(singleton x) → (Array/c a)
x : a

生成一个单元素的数组。

(= (array x) (singleton x))

3.10.3 数组合并🔗ℹ

procedure
(++ xs ys) → (Array/c a)
xs : (Array/c a)
ys : (Array/c a)

数组拼接。

Example:

> (++ (array 1 2 3) (array 3 2 1))
(Array 1 2 3 3 2 1)

procedure
(: x xs) → (Array/c a)
x : a
xs : (Array/c a)

相当于cons。

Examples:

> (: 1 (array))
(Array 1)
> (: 1 (array 2 3))
(Array 1 2 3)

procedure
(<:> x xs) → (Array/c a)
x : a
xs : (Array/c a)

往数组后面追加元素，相当于其他语言的push。

Examples:

> (<:> 1 (array))
(Array 1)
> (<:> 1 (array 2 3))
(Array 2 3 1)

procedure
(zip-with f xs ys) → (Array/c c)
  f : (-> a b c)
  xs : (Array/c a)
  ys : (Array/c b)

合并两条数组。

procedure
(zip xs ys) → (Array/c (cons/c a b))
xs : (Array/c a)
ys : (Array/c b)

合并两条数组。

3.10.4 列表属性🔗ℹ

procedure
(length xs) → exact-nonnegative-integer?
xs : (Array/c any/c)

数组长度。

Examples:

> (length (array))
0
> (length (array 1 2 3))
3

procedure
(empty? xs) → boolean?
xs : (Array/c any/c)

是否是空数组。

Examples:

> (empty? (array))
#t
> (empty? (array 1))
#f

3.10.5 子列表操作🔗ℹ

procedure
(head xs) → (Maybe/c a)
xs : (Array/c a)
(tail xs) → (Maybe/c a)
xs : (Array/c a)

Examples:

> (head (array))
(Nothing)
> (head (range 10 20))
(Just 10)
> (tail (array))
(Nothing)
> (tail (range 10 20))
(Just 19)

procedure
(take-while f xs) → (Array/c a)
  f : (-> a boolean?)
  xs : (Array/c a)
(drop-while f xs) → (Array/c a)
  f : (-> a boolean?)
  xs : (Array/c a)

Examples:

> (take-while even? (array 2 4 7 8 10))
(Array 2 4)
> (drop-while even? (array 2 4 7 8 10))
(Array 7 8 10)

procedure
(take n xs) → (Array/c a)
  n : exact-integer?
  xs : (Array/c a)
(take-right n xs) → (Array/c a)
  n : exact-integer?
  xs : (Array/c a)
(drop n xs) → (Array/c a)
  n : exact-integer?
  xs : (Array/c a)
(drop-right n xs) → (Array/c a)
  n : exact-integer?
  xs : (Array/c a)

Examples:

> (take 10 (array 1 2 3 4))
(Array 1 2 3 4)
> (drop -1 (array 1 2 3 4))
(Array)

procedure
(filter f xs) → (Array/c a)
  f : (-> a boolean?)
  xs : (Array/c a)
(reject f xs) → (Array/c a)
  f : (-> a boolean?)
  xs : (Array/c a)

过滤列表。

Examples:

> (filter even? (array 1 2 3 4))
(Array 2 4)
> (reject even? (array 1 2 3 4))
(Array 1 3)

3.10.6 数组查找🔗ℹ

procedure
(find f xs) → (Maybe/c a)
f : (-> a boolean?)
xs : (Array/c a)

Examples:

> (find (= 1) (array 3 1 2))
(Just 1)
> (find (= (Just 1)) (array nothing nothing (Just 2)))
(Nothing)
> (find (= nothing) (array nothing nothing (Just 2)))
(Just (Nothing))

procedure
(member? a xs) → (Maybe/c Eq?)
a : Eq?
xs : (Array/c Eq?)

Examples:

> (member? 1 (array))
#f
> (member? 2 (array 1 2 3))
#t

3.10.7 数组转换🔗ℹ

procedure
(reverse xs) → (Array/c a)
xs : (Array/c a)

反转数组。

procedure
(sort-by f xs) → (Array/c a)
  f : (-> a a boolean?)
  xs : (Array/c a)
(sort xs) → (Array/c a)
  xs : (Array/c a)

sort默认升序排序。

(define sort (sort-by <))

procedure
(filter-map f xs) → (Array/c b)
f : (-> a (Maybe/c b))
xs : (Array/c a)

即要filter又要map。

Examples:

> (define (f x)
    (if (< x 0)
        nothing
        (Just (add1 x))))
> (filter-map f (array -1 1 -2 2))
(Array 2 3)

procedure
(partition f xs) → (cons (Array/c a) (Array/c a))
f : (-> a boolean?)
xs : (Array/c a)

挑出两堆数组，左组满足f条件，右组不足。

procedure
(span f xs) → (cons/c (array a) (array a))
f : (-> a boolean?)
xs : (Array/c a)

从头寻找满足f的元素，直到未满足为止；返回一组满足元素的集合，及剩下元素集合。

Examples:

> (span (λ (x) (< x 3)) (array 1 2 3 4 1 2 3 4))
'(#<Array: 1 2> . #<Array: 3 4 1 2 3 4>)
> (span (λ (x) (< x 9)) (array 1 2 3))
'(#<Array: 1 2 3> . #<Array:>)

procedure
(split-at n xs) → (cons (Array/c a) (Array/c a))
n : exact-nonnegative-integer?
xs : (Array/c a)

按位置分割一个数组。

Examples:

> (split-at 0 (array 1 2 3))
'(#<Array:> . #<Array: 1 2 3>)
> (split-at 10 (array 1 2 3))
'(#<Array: 1 2 3> . #<Array:>)
> (split-at 2 (array 1 2 3))
'(#<Array: 1 2> . #<Array: 3>)

procedure
(group-by f xs) → (Array/c (Array/c a))
  f : (-> a a boolean?)
  xs : (Array/c)
(group xs) → (Array/c (Array/c a))
  xs : (Array/c a)

按条件f分组。

procedure
(array-adjust f i xs) → (Array/c a)
  f : (-> a a)
  i : exact-nonnegative-integer
  xs : (Array/c a)

更新i元素。

Examples:

> (array-adjust add1 0 (array 1 2 3))
(Array 2 2 3)
> (array-adjust add1 1 (array))
(Array)
> (array-adjust add1 10 (array 1 2 3))
(Array 1 2 3)

procedure
(array-update i x xs) → (Array/c a)
  i : exact-nonnegative-integer?
  x : a
  xs : (Array/c a)

更新i元素。

3.10.8 数组解构🔗ℹ

procedure
(array-get i xs) → (Maybe/c a)
i : exact-nonnegative-integer?
xs : (Array/c a)

获取第i - 1个元素。

Examples:

> (array-get 0 empty)
(Nothing)
> (array-get 10 (array 1 2 3))
(Nothing)
> (array-get 1 (array 1 2 3))
(Just 2)

procedure
(array-index a xs) → (Maybe/c exact-nonnegative-integer?)
a : Eq?
xs : (Array/c Eq?)

查看元素在哪个位置。

Examples:

> (array-index 'a empty)
(Nothing)
> (array-index (Just "a") (array nothing (Just "b") (Just "a")))
(Just 2)

procedure
(foldl f acc xs) → a
  f : (-> a b a)
  acc : a
  xs : (Array/c b)
(foldr f acc xs) → a
  f : (-> b a a)
  acc : a
  xs : (Array/c b)

3.10.9 数组特有语法🔗ℹ

syntax
(for/array (条件 ...) (代码体 ...))
(for*/array (条件 ...) (代码体 ...))

类似for/list、for*/list，结果产生的是array。

Examples:

> (for/array ([n (in-range 1 10)]) (+ n n))
(Array 2 4 6 8 10 12 14 16 18)
> (for*/array ([n (in-range 1 10)] [m (array "hello" "world")]) (array n m))
(Array
1
"hello"
1
"world"
2
"hello"
2
"world"
3
"hello"
3
"world"
4
"hello"
4
"world"
5
"hello"
5
"world"
6
"hello"
6
"world"
7
"hello"
7
"world"
8
"hello"
8
"world"
9
"hello"
9
"world")

1	简介
2	新朝雅语
3	数据结构
4	标准库

3.1	函数
3.2	Show(生成可读字符串)
3.3	Eq（相等比较）
3.4	Ord（大小比较）
3.5	Functor（函子）
3.6	Applicative（应用函子）
3.7	Monad（单子）
3.8	JSON
3.9	Maybe
3.10	数组
3.11	Map

3.10.1	数组定义
3.10.2	构造新数组
3.10.3	数组合并
3.10.4	列表属性
3.10.5	子列表操作
3.10.6	数组查找
3.10.7	数组转换
3.10.8	数组解构
3.10.9	数组特有语法