1.5 常量、变量、表达式

常量的声明

//圆周率是永恒不变的
const pi float32 = 3.14

变量的声明

//半径是实时变化的
var radius int

表达式
将常量变量使用运算符连接起来的式子

//面积计算的表达式
var area = pi*radius*radius

动态检测常量和变量的类型、

//动态判别类型
const LightSpeed = 300000
var isClever = false
func main() {
    //int
    fmt.Println("常量LightSpeed的实际类型是%T\n",LightSpeed)
    //bool
    fmt.Println("变量isClever的实际类型是%T\n",isClever)
}   

一次性声明多个常量或变量

//一次性声明多个
const(
    Chidao = 40000
    ChinaArea int = 960
)
var(
    fug = "hello"
    shid int = 123
)

在函数内，可以将变量的声明和赋值合二为一

func main() {
    //变量的声明赋值合二为一，这种声明方式只能在函数内部
    dann := 456.78
    fmt.Printf("type=%T,value=%v\n",dann,dann)
}   

更多变量声明的例子、

//声明布尔型变量
//var isStupid bool = true//真
//var isStupid bool = false//假
var isStupid bool

/*声明数值型变量*/
//var age int = 60
var age int
//var rmb float32 = 0.5
var rmb float32
//复数
//var vector complex64 = 3+4i
var vector complex64

//声明字符串变量
//var name string = "张全蛋"
var name string

/*声明复合型变量*/
//10长度的整型数组
//var ages [10]int = [10]int{1,2,3,4,5,6,7,8,9,0}
var ages [10]int

//可变长的整型切片
//var heights []int = []int{1,2,3}
var heights []int

//映射（键1：值1，键2：值2...）
//var kpi map[string]int = map[string]int{"代码量":10000,"注释量":3000}
var kpi map[string]int

var weight int = 300
//整型指针，weightPointer存放的不是300，而是放置300的内存地址
//var weightPointer *int = &weight
var weightPointer *int

//定义公有的（首字母大写，否则包内私有）接口Animal
//Go语言是强类型语言，但是空接口interface{}可以代指任何类型
var Animal interface{}

//结构体
//var person struct {
//  name string
//  age int
//  rmb float32
//}
var person struct{}

//声明函数变量
//var eat func() = func() {
//  fmt.Println("我是个吃货")
//}
var eat func(a int,b float64)bool

func main() {
    /*
    fmt.Printf格式化打印
    %T 类型占位符
    %v 值占位符
    */
    fmt.Printf("【是否愚蠢】的类型是%T，值是%v\n",isStupid,isStupid)
    fmt.Printf("【年龄】的类型是%T，值是%v\n",age,age)
    fmt.Printf("【资产】的类型是%T，值是%v\n",rmb,rmb)
    fmt.Printf("【向量】的类型是%T，值是%v\n",vector,vector)
    fmt.Printf("【姓名】的类型是%T，值是%v\n",name,name)
    fmt.Printf("【年龄们】的类型是%T，值是%v\n",ages,ages)
    fmt.Printf("【身高们】的类型是%T，值是%v\n",heights,heights)
    fmt.Printf("【KPI】的类型是%T，值是%v\n", kpi, kpi)
    fmt.Printf("【存体重的地址】的类型是%T，值是%v\n",weightPointer,weightPointer)
    fmt.Printf("【人】的类型是%T，值是%v\n", person, person)
    fmt.Printf("【饕餮】的类型是%T，值是%v\n",eat,eat)

}