go 入門教程變量

變量定義要求 ：Go 語言變量名由字母、數字、下劃線組成，其中首個字符不能爲數字

在描述變量定義以前，先描述下go 語言的結構

package main

import "fmt"
import "math"

func main()  {

 // 定義單一變量
     var age =18
    fmt.Println("my age is ",age)   
}

輸出：my age is  18

// 定義多個變量

var width,height int = 100,50
    fmt.Println("width is ",width,"height is",height)

    輸出： width is  100 height is 50

var (
        name = "zhangsan"
        age = 18
        job = "go"
        salary int
    )
    fmt.Println(" his name is",name, "age is",age, "job is",job, "salary is",salary)

    輸出：  his name is zhangsan age is 18 job is IT salary is 0

go 的簡短聲明

簡短聲明的要求， := 左邊的變量都有初始值 ,不然報錯 例如 assignment mismatch: 3 variable but 2 values

name,age,job := "zhangsan",18,"IT"
    fmt.Println(name,age,job)

輸出 ：zhangsan 18 IT

簡短聲明的語法要求 := 操做符的左邊至少有一個變量是還沒有聲明的

x,y :=20,30
    fmt.Println("x is",x,"y is ",y)
    y,z := 40,50 
    fmt.Println("y is",y,"z is ",z)

正常輸出： 

x is 20 y is  30
y is 40 z is  50

x,y :=20,30
x,y := 40,58
fmt.Println("x is",x ,"y is",y)

報錯  no new variables on left side of :=，左邊並無還沒有聲明的變量