Lei's Blog - 《Programming F#》读书笔记三

索引

笔记

数组：

let x = [| 1;1;3;5|]

let x = [| 1..10 |]

let x = [| for i in 1..10 –> i*i |]

let y = x.[1]

x.[1] <- 20

let z = x.[0..3]

let z = x.[6..]

let z = x.[..6]

let z = x.[*]

let len = Array.length x

let exists = Array.exists (fun item –> item>50) x         //判断数组是否满足给定条件

Array.init 根据索引初始化数组

let z = Array.init 10 (fun index –> index * 10)

Array.zeroCreate 使用默认值初始化数组

let z:int array = Array.zeroCreate 10          //初始化为0

let z:string array = Array.zeroCreate 10      //初始化为null

用于模式匹配：

let myMatch =

     function

     | null –> printf “匹配到null”

     | [| |] –> printf “匹配到空数组”

     | [| x |] –> printf “匹配到一个元素的数组”

     | [| x;y |] –> printf “匹配到两个元素的数组”

     | _ –> printf “匹配到更多元素的数组”

数组相等的判断

F#中数组相等比较的是数组的内容，而.net中比较的数组的引用

let eq = [| 0;1;2 |] = [| 0..2 |]   //相等

let eq = [| 0;1;2 |] = [| 0..10 |] //不等

规则数组

let x:int [,] = Array2D.zeroCreate 3 3

let y = x.[1,1]

x.[1,1] <- 30

let y = x.[*,1..2]

不规则数组，数组的数组

let x:int [][] = Array.zeroCreate 3;;

循环：

while循环

let mutable i= 10

while i>0 do

      printf “%d;” i

      i <- i – 1

   for循环

for i = 1 to 10 do

      printf “%d;” i

for i = 10 downto 1 do

      printf “%d;” i

for i in 1..10 do

       printf “%d;” i

F#中没有break和continue，要达到类似的目的，必须使用while语句。

for循环中进行模式匹配：

> for a,b in [for x in 1..10 -> (x,x*x)] do printfn "%d" (a+b);;
2
6
12
20
30
42
56
72
90
110
val it : unit = ()

异常：

自定义F#中的异常

exception WebSiteNotFound of string

exception Timeout

捕捉和抛出异常

try

      raise WebSiteNotFound(“http://myWebsite.com”)

with

| :? FileNotFoundException

       -> printf “.Net FileNotFoundException”

| :? IOException as ex

     -> printf “.Net IOException:%s” ex.Message

| WebSiteNotFound(webSite)

     -> printf “F# WebSiteNotFound:%s” webSite

| Timeout

    -> printf “F# Timeout”

| _ as ex

    -> reraise ex   //重新抛出异常

finally

      printf “finally”

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Contents

《Programming F#》读书笔记三

索引

笔记