Golang base--control statement

Control statements for the Go Basics

Supplemental knowledge

• Pointer
  • Unlike other languages, pointer arithmetic is not supported in Go -> , and a selector is used . to manipulate the members of the pointer target object directly.
• Operator & takes the address of the variable, using * indirect access to the target object through the pointer
• Default value bit nil, not NULL

• The instance code is as follows

  //指针的使用package mainimport "fmt"func main() {    a := 1          //定义一个变量，类型位int    a++             //必须单独放一行    var p *int = &a // 指针p指向a的内存地址    fmt.Println(p)  //访问p    fmt.Println(*p) //取p内存地址指向的值}

  Run results
  shell 0xc04200e0b8 //内存地址 2 //地址指向的值

Judging if control statements

• conditional expression without parentheses

• Supports an initialization expression (which can be in parallel mode)

• The left curly brace and conditional statement or else on the same line

• Supports when row mode

• The variable in the initialization statement is the block level, and the variable with the same name outside the bin
  EG1:

  //if语句:初始化语句a :1package mainimport (    "fmt")func main() {    a := 10    if a := 1; a > 0 {    //此时a是局部变量，作用域只在if语句内        fmt.Println(a)       }    fmt.Println(a)}

  EG2:

  //if..else语句：同时判断两种情况package mainimport  "fmt"func main() {    a := 10    if a, b := 1, 2; a > 1 {        fmt.Println(a)    } else {        fmt.Println(b)    }    fmt.Println(a)} /*output210*/

For Loop statement

• Go is only for a loop statement keyword, but it supports 3 different forms
• Initialization and progression expressions can be multiple values
• The conditional statement is re-examined each time, so it is not recommended to use a function in a conditional statement, try to calculate the condition in advance and replace it with a variable or constant

• The left brace must be on the same line as the conditional statement
  EG1: Infinite loop

   //For statement: Normal cycle Package main import ("FMT") func Main () {A: = 1 for {a++ if a >} fmt. Println (A)} FMT. Println ("Over")}  

  eg2:for conditional expression

   //for conditional expression Package Mainimport ("FMT") func Main () {A: = 1 for a < 3 {//conditional expression a++ FMT. Println (A)} FMT. Println ("Over")}  

  Eg3: most common

   //for: Step expression, most common package mainimport ("FMT") func Main () {A: = 1 for I: = 0; i < 3; i++ {//Step setting: When I<3, control a a++ fmt. Println (A)} FMT. Println ("Over")}  

  Note: The variable declared in the for loop disappears after each loop, and the scope is only valid in this loop

    package Mainimport "FMT" Func Main () {for i: = 0; i < 3; i++ {A: = 1 fmt. PRINTLN (&a)//output A memory address}}/* output 0xc04204a0800xc04204a0880xc04204a0b0*/ 

SELECT statement Switch

• You can use any type or expression as a conditional statement
• No write break is required, once the condition meets automatic termination
• If you want to continue with the next case, you need to use fallthrough keywords
• Supports an initialization expression (which can be used in parallel mode), with a semicolon on the right

• The left brace must be on the same line as the conditional statement

• EG1: The most classic usage

  /*检查a:如果a=0;输出a =0;如果a=1;输出a=1;...如果条件都不满足：默认输出None*/package mainimport (    "fmt")func main() {    a := 1    switch a {    case 0:        fmt.Println("a=0")    case 1:        fmt.Println("a=1")    default:        fmt.Println("None")    }}

• EG2: Conditions satisfy multiple conditions at the same time, using keywordsfallthrough

  /*同时满足多种情况，使用关键词fallthrough*/package mainimport "fmt"func main() {    a := 1    switch {    case a >= 0:        fmt.Println("a=0")        fallthrough //fallthrough用法，类似于elif    case a >= 1:        fmt.Println("a=1")    default:        fmt.Println("None")    }}

• Eg3:swith followed by initialization statement

  /*swtich后面跟初始化语句： 初始化语句中的变量作用域在switch语句中*/package mainimport "fmt"func main() {    switch a := 1; {    case a >= 0:        fmt.Println("a=0")        fallthrough //fallthrough用法，类似于elif    case a >= 1:        fmt.Println("a=1")    default:        fmt.Println("None")    }}

  Jump Statement Goto,break,continue

• Three syntax can be used in conjunction with a label
• Label names are case-sensitive and can cause compilation errors if not used
• Break and continue mate tags can be used to jump out of multi-layer loops

• Goto is the adjustment of the execution position, which is not the same as the result of the other 2 statement mates label

• Eg1:break statements

  //break跳转语句,可以跳转出多存循环package mainimport "fmt"func main() {LABEL1: //定义标签   for { //这是一个无线循环       for i := 0; i < 10; i++ { //有限循环           print(i)  //循环四遍跳出循环           if i > 3 {               fmt.Println("OK")               break LABEL1 //直接跳出N层循环           }       }   }   fmt.Println("OK")}

• Eg2:goto statement, transfer to a loop, continue execution

  package mainimport  "fmt"func main() {    for {                           //这是一个无线循环        for i := 0; i < 10; i++ {    //有限循环            if i > 3 {                goto LABEL1         //返回到LABEL1层继续执行            }        }    }LABEL1: //使用goto跳转的话，尽量将标签放goto语句之后    fmt.Println("OK")}

• Eg3:continue statement, internal for Each loop after encountering continue, returns LABEL1

  // continue语句package mainimport "fmt"func main() {LABEL1:   for i := 0; i < 10; i++ { //有限循环       for { //无限循环           fmt.Println(i)           continue LABEL1     // 遇到LABEL1后，不会继续执行，而是跳到同级别           fmt.Println("here") //永远不会执行这项操作       }   }   fmt.Println("OK")   //循环十次，最后执行}