常量介绍

示例

package main

import (
	"fmt"
)

func main() {
	const name = "tom"
	fmt.Println(name)
	const tax float64 = 0.8
	fmt.Println(tax)
}

go run const.go 
tom
0.8

package main

import (
	"fmt"
)

func main() {
	const a int
	fmt.Println(a)
}

go run const.go 
# command-line-arguments
./const.go:8:8: missing init expr for a

package main

import (
	"fmt"
)

func getVal() {
	fmt.Printf("测试")
}
func main() {
	const b = 9 / 3
	fmt.Println(b)
	//const c = getVal()
	//fmt.Println(c)
}

go run const.go 
3

package main

import (
	"fmt"
)

func getVal() {
	fmt.Printf("测试")
}
func main() {
	//const b = 9 / 3
	//fmt.Println(b)
	const c = getVal()
	fmt.Println(c)
}

go run const.go 
# command-line-arguments
./const.go:13:12: getVal() (no value) used as value

package main

import (
	"fmt"
)

func getVal() {
	fmt.Printf("测试")
}
func main() {
	//const b = 9 / 3
	//fmt.Println(b)
	//const c = getVal()
	//fmt.Println(c)
	num := 9
	const b = num / 3
	fmt.Println(b)
}

go run const.go 
# command-line-arguments
./const.go:16:12: num / 3 (value of type int) is not constant

常量比较简单的写法

package main

import (
	"fmt"
)

func getVal() {
	fmt.Printf("测试")
}
func main() {
	const (
		a = 1
		b = 2
	)
	fmt.Println(a, b)
	const (
		c = iota
		d
		e
	)
	fmt.Println(c, d, e)
}

go run const.go 
1 2
0 1 2