go的switch

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package main

import(
	"fmt"	
)

func testIf(){	
	var num int =2
	if num == 1{
		fmt.Printf("num:%d num==1 \n",num)
	}else if num == 2{
		fmt.Printf("num:%d num==2 \n",num)
	}else if num == 3{
		fmt.Printf("num:%d num==3 \n",num)
	}else if num == 4{
		fmt.Printf("num:%d num== 4 \n",num)
	}else{
		fmt.Printf("num:%d num== 5 \n",num)
	}
	// fmt.Printf("num3:%d \n",num)  //   num 是在函数内定义的,在在整个函数的生命周期内都有效
}



func testSwitch(){
	var num int =2
	switch num {
	case 1 :
		fmt.Printf("num:%d num==1 \n",num)		
	case 2 :
		fmt.Printf("num:%d num==2 \n",num)
	case 3 :
		fmt.Printf("num:%d num==3 \n",num)
	case 4 :
		fmt.Printf("num:%d num==4 \n",num)
	case 5 :
		fmt.Printf("num:%d num==5 \n",num)
	}
}


func testSwitchV2(){	
	switch num :=6; num {
	case 1 :
		fmt.Printf("V2num:%d num==1 \n",num)		
	case 2 :
		fmt.Printf("V2num:%d num==2 \n",num)
	case 3 :
		fmt.Printf("V2num:%d num==3 \n",num)
	case 4 :
		fmt.Printf("V2num:%d num==4 \n",num)
	case 5 :
		fmt.Printf("V2num:%d num==5 \n",num)
	default:
		fmt.Printf("invalid num=%d\n",num)
	}
	// fmt.Printf("V2num:%d num==5 \n",num)  // undefined: num   num只在switch语句块中有效,语句块结束,num就没了
}


func testSwitchV3(){	
	switch num :=2; num {
	case 1,2,3,4,5 :
		fmt.Printf("V3 num:%d num>=2 and num <=5 \n",num)
	case 6,7,8,9,10 :
		fmt.Printf("V3 num:%d num>=6 and num <=10 \n",num)	
	default:
		fmt.Printf("num>10 num=%d\n",num)
	}
	// fmt.Printf("V2num:%d num==5 \n",num)  // undefined: num   num只在switch语句块中有效,语句块结束,num就没了
}



func testSwitchV4(){	
	switch num :=666; {
		case num>=0 && num <=25  :
			fmt.Printf("V3 num:%d num>=0 and num <=25 \n",num)
		case num>25 && num <=50   :
			fmt.Printf("V3 num:%d num>25 and num <=50 \n",num)
		case num>50 && num <=75   :
			fmt.Printf("V3 num:%d num>50 and num <=75 \n",num)
		case num>75 && num <=100 :
			fmt.Printf("V3 num:%d num>75 and num <=100 \n",num)
		default:
			fmt.Printf("invalid num=%d\n",num)
	}
	// fmt.Printf("V2num:%d num==5 \n",num)  // undefined: num   num只在switch语句块中有效,语句块结束,num就没了
}


func testSwitchV5(){
	var num =30	
	switch  {
	case num>=0 && num <=25  :
		fmt.Printf("V3 num:%d num>=0 and num <=25 \n",num)		
	case num>25 && num <=50   :
		fmt.Printf("V3 num:%d num>25 and num <=50 \n",num)	
		fallthrough
	case num>50 && num <=75   :
		fmt.Printf("V3 num:%d num>50 and num <=75 \n",num)	
		fallthrough
	case num>75 && num <=100 :
		fmt.Printf("V3 num:%d num>75 and num <=100 \n",num)	
	default:
		fmt.Printf("invalid num=%d\n",num)
	}
	// fmt.Printf("V2num:%d num==5 \n",num)  // undefined: num   num只在switch语句块中有效,语句块结束,num就没了
}



func testMulti(){
	for i:=1;i<10;i++{
		for j :=1;j<=i;j++{
			fmt.Printf("%d * %d = %d\t",j,i,j*i)
		}
		fmt.Println()
	}
}

func main(){	
	testIf()
	testSwitch()
	//testSwitchV2()
	//testSwitchV3()
	//testSwitchV4()
	//testSwitchV5()
	//testMulti()
}