Go branch and loop

go Branches and loops

if-else sentence

go Of if-else Judgment statement , and js It's like , The grammar is as follows

if condition {
    
    
} else if condition {
    
    
} else {
    
    
}

When condition When the conditions are met, execute { } The code in , Not satisfied with the implementation of else Back

func main()  {
    
   number := 55
    if number >=90 && number <= 100 {
      //  The beginning of braces should be on the same line as the keyword 
        							// go By default, no line ends with  ;  An error will be reported if the line changes  
      fmt.Println(" good ")
   } else if number >= 60 && number <= 90 {
      // else if  There must be conditions behind 
      fmt.Println(" good ")
   } else {
     			// else  There can be no conditions behind 
      fmt.Println(" fail, ")
   }
}

for Loop statement

for yes Go The only loop statement in language .Go There are no other languages in the language, such as python Medium while loop .

complete for loop grammar

for initialisation; condition; post {
      
}

The initialization statement is executed only once . After loop initialization , Cycle conditions will be checked . If the result of the condition is true , be {} The inner loop body will execute , Then perform post sentence .post Statement will execute after each successful loop iteration . In execution post After the statement , The conditions will be checked again . If true, Then the loop will continue to execute , otherwise for The cycle will end .（ Translation notes ： This is typical for Loop three expressions , The first is the initialization expression or assignment statement ; The second is the expression of cyclic condition determination ; The third is the loop variable correction expression , That is to say post ）

for Cyclic 5 Method of use

1.  Index based loop 
func main() {
    
    //  Loop printing  0-9
	for i := 0; i < 10; i++ {
    
		fmt.Println(i)
	}
}
2.  External initialization 
func main(){
    
    i := 0    // i  The scope of is expanded 
    for ; i<10; i++{
       // ;  Don't omit 
        fmt.Println(i)
    }
}
3.  The loop variable correction expression is written internally 
func main(){
    
    i := 0    // i  The scope of is expanded 
    for ; i<10; {
      //  Write only conditions   It can be omitted  ;
        fmt.Println(i)
        i++
    }
}

func main(){
    
    i := 0    // i  The scope of is expanded 
    for i<10 {
      //  Write only conditions   It can be omitted  ;
        fmt.Println(i)
        i++
    }
}
4.  Omit the cycle condition 
func main(){
    
    for ; ; {
      //  here  ;  You can omit it 
        fmt.Println(" Dead cycle ")
    }
}

func main(){
    

    for  {
      //  here  ;  You can omit it 
        fmt.Println(" Dead cycle ")
        break  //  You can add  break  Keyword to terminate , There are also  continue  keyword , Skip the following code directly , Execute next cycle 
    }
}

5.  Iteration based loop 
func main(){
    
	var a = [3]int[1, 25, 34]  //  Array 
    for i,value := range a {
       
        fmt.Println(i)   //  Indexes 
        fmt.Println(value) //  value 
    }
}

go Kind of for Same cycle Like other languages , It can also be executed A nested loop , The following list is printed 9 x 9 Multiplication table

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

switch sentence

switch It's a conditional statement , Used to compare the value of an expression with a list of possible matches , And execute the corresponding code block according to the matching situation . It can be thought of as an alternative to multiple if else The common way of clause .

// 1  Usage 1 
	name:="tom"
	switch name {
    
	case "lxx":
		fmt.Println("lxx")
	case "tom":
		fmt.Println("tom")
	}
//  Usage mode 2  Without conditions 
    name:="tom"
    switch  {
    
        case name=="lxx":
        fmt.Println("lxx")
        case name=="tom":
        fmt.Println("tom")
    }
//  Usage mode 3  Multiple conditions 
	name:="tom"
	switch name {
    
	case "lxx","jason":  //  perhaps 
		fmt.Println("lxx")
	case "tom","marry":
		fmt.Println("tom")
	}

	name := "tom"
	switch {
    
	case name == "lxx" || name == "jason": //  perhaps 
		fmt.Println("lxx")
	case name == "tom", name == "marry":
		fmt.Println("tom")
	}
// 4  The way 4 ,default Use , Does not meet all case after , perform 
	name:="tom"
	switch name {
    
	case "lxx":
		fmt.Println("lxx")
	case "tom":
		fmt.Println("tom")
	default:
		fmt.Println(" I don't know who it is ")
	}

// 5 fallthrough Use   Just see this keyword , Unconditionally execute the next case
	name:="lxx"
	switch name {
    
	case "lxx":
		fmt.Println("lxx")
		fallthrough
	case "tom":
		fmt.Println("tome")
		fallthrough
	default:
		fmt.Println(" I don't know who it is ")

	}

matters needing attention :

1. case Duplicate options are not allowed after , If repeated, an error will be reported