Go——基础（2）

var p *int

i:=2
p=&i

func main (){
    i,j:=12,31
    p:=&i//p是指向i的指针
    fmt.Println(*p)
    *p=21//通过指针改变i的值
    
    p=&j//p指向j,因为在前面p已经声明过了，所以不用:=
    *p=*p/2//通过指针对j进行除法运算
    
}

import "fmt"

type jiegou struct{
    X int 
    Y int 
}

func main (){
    fmt.Println(jiegou{1,2})
}
//输出结果为{1,2}

type Vertex struct {
    x int
    y int
}

func main (){
    v:=Vertex{1,2}
    v.x=3
    fmt.Println(v.x)
}//输出：3

type Vertex struct {
    x int
    y int
}


func main (){
    v:=Vertex{1,2}
    p:=&v
    p.x=3
    fmt.Println(v)//结果为（3，2）
}

type Vertex struct {
    x int
    y int
}
func main (){
    v1=Vertex{1,2}
    v2=Vertex{x:1}//默认y:0
    v3=Vertex{}//默认x:0,y:0
    p=&Vertex{1,2}//p是指向{1,2}的结构体指针
}

var a[10]int 

var main (){
    var a[2]string
    a[0]="hello"
    a[1]="world"
    
    b:=[6]int{1,2,3,4,5,6}
}

a[1:4]

func main (){
    b:=[6]int {1,2,3,4,5,6}
    
    var s[]int = b[1:4]//切片s包含b1-b3
}

func main (){
    names:=[4]string {
        "LiHua"
        "Mike"
        "Tom"
        "ha"
    }
    a:=names[0:2]
    a[0]="Jack"
    fmt.Pritln(names)//names[0]就改为了jack
    
}

[3]bool{true,false,true}

[]bool{true,false,true}

func main (){
    q:=[]int {1,2,3,4,5,5}
    p:=[]bool{true,false}
}

var a[10]int 
a[0:10]
a[:10]
a[0:]
a[:]是等价的

func main (){
    s:=[]int {1,2,3,4,5,6}
    
    s=s[:0]//使其长度为0
    s=s[0:4]//重新切片扩展切片
    s=s[2:]//舍弃前两个值
}

a:=make([]int,2,2)//切片a的长度为2，容量为2

func main (){
    a:=make([]int 5)
    printslice("a",a)b
    
    b:=make([]int,0,5)
    printslice("b",b)
    
    c:=b[0:2]
    printslice("c",c)
    
    d:=c[2:5]
}

func main(){
    a:=[][]string{
		[]string{"_", "_", "_"},
		[]string{"_", "_", "_"},
		[]string{"_", "_", "_"},
}
}

func main (){
    var s[]int
    
    s=append(s,0)//添加一个空切片

    s=append(s,1)
    
    s=append(s,2,3,4)//可以一次性添加多个元素
}

var pow[]{1,2,3,4,5,6}
func main (){
    for i;v=range pow{
        fmt.Println("%d,%d",i,v)
}
}

for i, _ := range pow//只返回下标
for _, value := range pow//只返回值

for i := range pow

type Vertex struct{
	Lat,Long float64
}

var m map[string] Vertex

func main (){
    m=make(map[string]Vertex)
    m["Bell Labs"]=Vertex{
       	40.2,-32 
    }
    fmt.Println(m["Bell Labs"])
}

var m map[string]Vertex{
    "Bell Labs":Vertex{
        2,3
    }
    "Google":Vertex{
        2,4
}
}

var m = map[string]Vertex{
	"Bell Labs": {40.68433, -74.39967},
	"Google":    {37.42202, -122.08408},
}

m[key]=elem

elem=m[key]

delete(m,key)

elem,ok=map[key]

func main (){
    m:=make(map[string]int)
    
    m["answer"]=19
 	m["answer"]=121
    
    delete(m,"answer")
    
    v,ok:=m["answer"]

}

func compute (fn func(float64,float64)float64)float64{
    return (fn(3,4))
}