FSharp-03-Collections

List

**List元素默认不可变**

定义List

• let list = []，空List
• let list = [1..10]，默认步长的List
• let list = [1..2..10]，步长为2的List
• let list = [1;2;3]，给定元素的List
• 注意list = [1,2,3]则是元组

exapmle

// 定义List
let list =[1..10]
list

index	value
0	1
1	2
2	3
3	4
4	5
5	6
6	7
7	8
8	9
9	10

// print
printfn $"%A{list}"
// answer
[1; 2; 3; 4; 5; 6; 7; 8; 9; 10]

// 步长-2
let list = [10..-2..0]
list

index	value
0	10
1	8
2	6
3	4
4	2
5	0

切片操作

let list = [0..10]
// [0; 1; 2; 3; 4; 5; 6; 7; 8; 9; 10]
printfn $"%A{list}"
list[1..2]

index	value
0	1
1	2

let list = [0..10]
// [0; 1; 2; 3; 4; 5; 6; 7; 8; 9; 10]
printfn $"%A{list}"
list[..2]

index	value
0	0
1	1
2	2

let list = [0..10]
// [0; 1; 2; 3; 4; 5; 6; 7; 8; 9; 10]
printfn $"%A{list}"
list[5..]

index	value
0	5
1	6
2	7
3	8
4	9
5	10

let list = [0..10]
// [0; 1; 2; 3; 4; 5; 6; 7; 8; 9; 10]
printfn $"%A{list}"
list[5..2]

(empty)

let list = [for i in 0 .. 10 -> i*i]
list

index	value
0	0
1	1
2	4
3	9
4	16
5	25
6	36
7	49
8	64
9	81
10	100

遍历

API

• list[1]
• list.Item(1)
• list.IsEmpty
• list.Length
• list.Head
• list.Tail
• List.contains 1 list

example

let list = [1; 2; 3]

// list.IsEmpty is false
printfn "list.IsEmpty is %b" (list.IsEmpty)

// list.Length is 3
printfn "list.Length is %d" (list.Length)

// list.Head is 1
printfn "list.Head is %d" (list.Head)

// list.Tail is [2; 3]
printfn "list.Tail is %A" (list.Tail)

// list.Tail.Head is 2
printfn "list.Tail.Head is %d" (list.Tail.Head)

// list.Tail.Tail.Head is 3
printfn "list.Tail.Tail.Head is %d" (list.Tail.Tail.Head)

// list.Item(1) is 2
printfn "list.Item(1) is %d" (list.Item(1)) 

// True
List.contains 1 list

拼接

API

• 用 ::拼接元素
• 用 @ 连接两个List
• List.zip list1 list2
• let list4, list5 = List.unzip list3

example

// List使用;分隔，用'[]'包住
let list1 = ["a"; "b"]
// ["a"; "b"]
printfn $"%A{list1}"

// 用 '::'拼接元素
let list2 = "c" :: list1
// ["c"; "a"; "b"] 
printfn $"%A{list2}"

// 用'@'连接两个List
let list3 = list1 @ list2
// ["a"; "b"; "c"; "a"; "b"]
printfn $"%A{list3}"

// zip 
let list1 = [1; 2; 3]
let list2 = [4; 5; 6]
let list3 = List.zip list1 list2
// [(1, 4); (2, 5); (3, 6)]
printfn $"{list3}"

index	Item1	Item2
0	1	4
1	2	5
2	3	6

// unzip 
let list1 = [1; 2; 3]
let list2 = [4; 5; 6]
//zip
let list3 = List.zip list1 list2
// [(1, 4); (2, 5); (3, 6)]
printfn $"{list3}"
// unzip
let list4, list5 = List.unzip list3
// [1; 2; 3]
printfn $"{list4}"
// [4; 5; 6]
printfn $"{list5}"

exercise

// 构造1到100的奇数List 
let oddList = [1..2..100]
printfn $"%A{oddList}"

// 构造1到100的偶数List
let evenList = [2..2..100]
printfn $"%A{evenList}"

Seq

**Sequence是一个可枚举的序列，不支持切割操作**

定义Seq

// Sequences can use yield and contain subsequences
let seq1 = 
    seq {
        // "yield" adds one element
        yield 0
        yield 1
        yield 2

        // "yield!" adds a whole subsequence
        yield! [3..10]
    }
seq1

遍历

• Seq.isEmpty
• Seq.length
• Seq.head
• Seq.tail
• Seq.item 1

let seq1 = seq{0..10}
// seq [0; 1; 2; 3; ...]
printfn $"%A{seq1}"

// functions
// Seq.isEmpty is false
printfn "Seq.isEmpty is %b" (Seq.isEmpty seq1)
// Seq.length is 11
printfn "Seq.length is %d" (seq1 |>Seq.length)
// Seq.head is 0
printfn "Seq.head is %d" (seq1 |>Seq.head)
// Seq.tail.head is 1
printfn "Seq.tail.head is %d" (seq1 |>Seq.tail   |>Seq.head)
// Seq.tail.tail.head is 2
printfn "Seq.tail.tail.head is %d" (seq1 |>Seq.tail |>Seq.tail |>Seq.head)
// Seq.item 1  is 1
printfn "Seq.item 1  is %d" (seq1 |>Seq.item 1)

seq1

index	value
0	0
1	1
2	2
3	3
4	4
5	5
6	6
7	7
8	8
9	9
10	10

List与Seq

let list1 = [ 1; 2; 3 ]
// functions
printfn "Seq."
printfn "List.isEmpty is %b" (Seq.isEmpty list1)
printfn "List.length is %d" (list1 |>Seq.length)
printfn "List.head is %d" (list1 |>Seq.head)
printfn "List.tail.head is %d" (list1 |>Seq.tail   |>Seq.head)
printfn "List.tail.tail.head is %d" (list1 |>Seq.tail |>Seq.tail |>Seq.head)
printfn "List.item 1  is %d" (list1 |>Seq.item 1)

Seq.
List.isEmpty is false
List.length is 3
List.head is 1
List.tail.head is 2
List.tail.tail.head is 3
List.item 1  is 2

------------------------------------------------------------
// functions
printfn "List."
printfn "List.isEmpty is %b" (List.isEmpty list1)
printfn "List.length is %d" (list1 |>List.length)
printfn "List.head is %d" (list1 |>List.head)
printfn "List.tail.head is %d" (list1 |>List.tail   |>List.head)
printfn "List.tail.tail.head is %d" (list1 |>List.tail |>List.tail |>List.head)
printfn "List.item 1  is %d" (list1 |>List.item 1)

List.
List.isEmpty is false
List.length is 3
List.head is 1
List.tail.head is 2
List.tail.tail.head is 3
List.item 1  is 2

Seq与List进行转化

let list1= [0..10]
let seq1 = list1 |> Seq.ofList
let seq2 = list1 |> List.toSeq

Set

**Set中元素不可重复**

let set_1 = [1;2;3] |> set
let set_2 = [1;2;3] |> set
// set [1; 2; 3]
printfn $"{set_1}"
// set [1; 2; 3]
printfn $"{set_2}"

API

• set_1.IsSubsetOf(set_2)
• set_1.IsSupersetOf(set_2)
• set_1.IsProperSubsetOf(set_2)
• set_1.IsProperSupersetOf(set_2)
• set0.Count
• set_1 = set_2 // 比较结构相等（值）基础类型
• let set_3 = set_1.Add(0)
• Set.union set_4 set_3
• Set.intersect set_4 set_3

Map

let m=Map.ofList [(1,"cyan")]
m

key	value
1	cyan

let m=
    [
    (1,"cyan")
    2,"gauss"
    ]
    
    |> Map.ofList  
m

key	value
1	cyan
2	gauss

m.Add(1,"X")

key	value
1	X
2	gauss

let m2=m.Add(3,"csharp")
m2

key	value
1	cyan
2	gauss
3	csharp

m2.Keys
m2.Values

// [[1, cyan]; [2, gauss]; [3, csharp]]
m2 |>List.ofSeq |> printfn "%A"
m2.TryFind(1)
m2.TryFind(4)

let m = [for i in 1..100 -> (string(i), i*i)] |> Map

key	value
1	1
10	100
100	10000
11	121
12	144
13	169
14	196
15	225
16	256
17	289
18	324
19	361
2	4
20	400
21	441
22	484
23	529
24	576
25	625
26	676
… (more)