Go语言学习记录3——条件和循环语句

Posted 2022-02-10 康娜喵

一. 条件语句

go语言的循环语句长得像这样：
注意else要和 在同一行

if condition   
 else if condition 
 else 

//or
if condition   

除了这样，还有先执行statement再判断condition的语句

if statement; condition   

二.选择语句Switch

2.1 普通的Switch

Go中的Switch语句形如C语言:

package main

import (  
    "fmt"
)

func main()   
	finger := 8
    switch finger 
    case 1:
        fmt.Println("Thumb")
    case 2:
        fmt.Println("Index")
    case 3:
        fmt.Println("Middle")
    case 4:
        fmt.Println("Ring")
    case 5:
        fmt.Println("Pinky")
    default: //default case
        fmt.Println("incorrect finger number")
    

因为Go语言的特性当然也可以写成switch finger := 8; finger ,

2.2 多条件的Switch

package main

import (  
    "fmt"
)

func main()   
    letter := "i"
    switch letter 
    case "a", "e", "i", "o", "u":
        fmt.Println("vowel")
    default:
        fmt.Println("not a vowel")
    

这段语句中,不管letter是a、e、i、o、u中任意一个字母,都会输出vowel

2.3 无表达式的Switch

Switch的表达式可以默认,且默认的值是true,且case中可以放condition,若满足true的条件即可触发.

package main

import (  
    "fmt"
)

func main()   
    num := 75
    switch 
	case num == 75:
		fmt.Println("num is 75")
    case num >= 0 && num <= 50:
        fmt.Println("num is greater than 0 and less than 50")
    case num >= 51 && num <= 100:
        fmt.Println("num is greater than 51 and less than 100")
    case num >= 101:
        fmt.Println("num is greater than 100")
    

但此时的num并不能触发num is greater than 51 and less than 100，而只是输出了num is 75。

2.3 fallthrough

使用fallthrough关键字可以让某个case执行完后，继续执行，例如：

package main

import (  
    "fmt"
)

func main()   
    num := 75
    switch 
	case num == 75:
		fmt.Println("num is 75")
		fallthrough
    case num >= 0 && num <= 50:
        fmt.Println("num is greater than 0 and less than 50")
    case num >= 51 && num <= 100:
        fmt.Println("num is greater than 51 and less than 100")
    case num >= 101:
        fmt.Println("num is greater than 100")
    

/* outputs
num is 75
num is greater than 0 and less than 50
*/

三.循环

Go语言的循环是C风格的，形如这样：

for initialisation; condition; post   

刚好对标C语言的：

for (initialisation; condition; post)

当然，go也支持break、continue:

package main

import (  
    "fmt"
)

func main()   
    for i := 1; i <= 20; i++ 
        if i % 2 == 0 
            continue
         else if i > 10 
			break
		 else 
			fmt.Print(i, " ")
		
    

/* outputs
1 3 5 7 9 
*/