Introduction to go language (V) -- branch statement

Branch statement

if-else sentence

Code form

if  Boolean expression  {
    
	// Code block 
}else{
    
	// Code block 
}

go The branch statements in are the same as C Very similar in language , Just remove the brackets , Special attention is paid to if It can only be followed by Boolean expressions, not like C Same use 0 He Fei 0 To represent the truth value

Basic example
Here we borrow fmt Medium Scan To get the input of the keyboard to branch the input numbers and 0 The relationship between , The code is as follows

package main

import "fmt"

func main(){
    
	var a int
	fmt.Scan(&a);
	if a < 0{
    
		fmt.Printf("%v is smaller than 0\n", a)
	}else if a > 0{
    
		fmt.Printf("%v is bigger than 0\n", a)
	}else{
    
		fmt.Printf("%v is equal with 0\n", a)
	}
}

It can be seen that three times of operation are input respectively 9,-8,0 The results are different

First assign values and then judge examples
if-else Branch statements can also be assigned before judgment

package main

import "fmt"

func main(){
    
	if a:=-1;a < 0{
    
		fmt.Printf("%v is smaller than 0\n", a)
	}else if a > 0{
    
		fmt.Printf("%v is bigger than 0\n", a)
	}else{
    
		fmt.Printf("%v is equal with 0\n", a)
	}
}

switch sentence

go Medium switch And C It's very similar to , But we should pay attention to some of his characteristics

1. The default execution is to a case ends , No need to add break, If you want to execute the following... In sequence case You need to add... At the end fallthrough
2.case The judgment in can be a value , Multiple values or Boolean expressions

Single value switch Example
Except you don't have to add break Extraneous and C Almost the same

package main
import "fmt"

func main(){
    
	var m int
	fmt.Scan(&m)
	switch m{
    
	case 1:
		fmt.Printf("1\n")
	case 2:
		fmt.Printf("2\n")
	case 3:
		fmt.Printf("3\n")
	default:
		fmt.Printf("Error\n")
	}
}

Multivalued switch Example
Enter the month and pass switch Print the number of days corresponding to the month

package main
import "fmt"

func main(){
    
	var m int
	fmt.Scan(&m)
	switch m{
    
	case 1, 3, 5, 7, 8, 10, 12:
		fmt.Printf("31\n")
	case 2:
		fmt.Printf("28\n")
	case 4, 6, 9, 11:
		fmt.Printf("30\n")
	default:
		fmt.Printf("Error\n")
	}
}

Boolean expression switch Example
We use Boolean expression to judge the grade of students

package main
import "fmt"

func main(){
    
	var score int
	fmt.Scan(&score)
	switch {
    
	case score >= 90:
		fmt.Printf("A\n")
	case score >= 80 && score < 90:
		fmt.Printf("B\n")
	case score >= 70 && score < 80:
		fmt.Printf("C\n")
	default:
		fmt.Printf("D\n")
	}
}