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📜  F＃列表

📅  最后修改于: 2021-01-01 04:58:05             🧑  作者: Mango

F＃清单

List是相同类型元素的不可变集合。它不允许重复的元素。它保持元素的顺序。

F＃创建和初始化列表示例

有多种创建列表的方法。一些在下面描述。

let list = [1;2;3;4;5]            // You can create and initialize list at the same time

let list = [
     1
     2
     3
     4
     5
 ]        // Here, semicolon is optional, and you can pass each new element to new line

let list = [1 .. 5]    // You are allowed to initialize list by passing starting and last elements only.

F＃清单范例

let list = [1;2;3;4;5;6;7;8;9]
for i  in list do
 printfn "%d" i

输出：

1
2
3
4
5
6
7
8
9

F＃将新元素添加到列表中

您可以使用::(cons)运算符将新元素添加到列表中。让我们看一个例子。

let list = [1;2;3;4;5]
for i in list do
 printf "%d " i 
printfn "\n" 
let list2 = 0::list                // Adding new element here
for i in list2 do 
  printf "%d " i

输出：

1 2 3 4 5
0 1 2 3 4 5

两列表示例的F＃串联

您可以使用@运算符连接两个具有相同类型的列表。让我们来看一个例子。

let list1  = [1; 2; 3; 4; 5]
let list2  = [6; 7; 8; 9; 10]
let list3 = list1@list2             // Here, @ operator used for concatenation
for i in list3 do
 printfn "%d " i

输出：

1
2
3
4
5
6
7
8
9
10

F＃清单属性

F＃列表提供了重要的属性。它也有助于优化和维护代码。

Property Description
Head It returns first element of list.
Empty It returns empty list.
IsEmpty It returns true if list is empty
Length It returns number of elements.
Tail It returns list excluding first element.

F＃列表属性示例

let list = [ 1; 2; 3; 4; 5 ]

printfn "Is list Empty: %b" (list.IsEmpty)
printfn "Length of list is %d" (list.Length)
printfn "Head element of list is %d" (list.Head)
printfn "Tail element of Head in the list is %d" (list.Tail.Head)
printfn "Tail element of tail of head of list %d" (list.Tail.Tail.Head)
printfn "Element at 1 index is %d" (list.Item(1))

输出：

Is list Empty: false
Length of list is 5
Head element of list is 1
Tail element of Head in the list is 2
Tail element of tail of head of list 3
Element at 1 index is 2

在F＃中，list提供了用于对元素进行排序和搜索的内置函数。

F＃列表排序示例

let list = List.sort[23; 54; 12; 7; 43; 89; 0; 10; 90]
for i in list do
 printfn "%d" i

输出：

0
7
10
12
23
43
54
89
90

F＃列表搜索示例

List提供List.find()函数以在列表中查找元素。它返回第一个匹配的元素，如果找不到该元素，则抛出System.Collections.Generic.KeyNotFoundException异常。

let isFound number elem = elem = number 
let result = List.find (isFound 10) [ 1 .. 100 ]
printfn "%d " result

输出：

10

列表中的F＃压缩和解压缩功能

Zip函数将两个单值列表组合为一个元组列表。解压缩函数将一个元组列表分成两个单值列表。

F＃列表压缩示例

.
let zipExample list1 list2 =
 printf "Given Lists: \n List1: %A \n List2: %A" list1 list2
 List.zip list1 list2

let zippedlist = zipExample [1..10][1..10]
printf "\nResult(Zipped List):\n %A" zippedlist

输出：

Given Lists:
 List1: [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]
 List2: [1; 2; 3; 4; 5; 6; 7; 8; 9; 10]
Result(Zipped List):
 [(1, 1); (2, 2); (3, 3); (4, 4); (5, 5); (6, 6); (7, 7); (8, 8); (9, 9);
 (10, 10)]

F＃列表解压缩示例

let unzipExample zippedList =
 List.unzip zippedList

let unzippedList = unzipExample [(1,2); (3,4); (5,6)]
printf "\nFirst List: %A \nSecond List: %A" (fst unzippedList)(snd unzippedList)

输出：

First List: [1; 3; 5]
Second List: [2; 4; 6]