Day 005: Go language constants and iota

foreword

I majored in Java network security, but after participating in the internship (security research engineer), I found that most of the needs come from python and go, and Java also has but few. The company is more willing to accept handsome guys who can go, so I plan to take out one every day. Hour to learn the go language.

---

constant

In contrast to variables, constants are quantities that do not change. Once defined, it cannot be modified.
Constant keyword const.

const pi = 3.1415926

Bulk declaration:

const (
	status   = 200
	notfound = 404
)

When declaring constants in batches, if no value is written in a row, the default is the same as the previous row

const (
	n1 = 100
	n2
	n3
)

func main() {
    
    
	//pi = 123
	fmt.Println("n1:", n1)
	fmt.Println("n2:", n2)
	fmt.Println("n3:", n3)
}

iota

iota is a constant counter in golang and can only be used in constant expressions.

• iota will be defined as 0 when const appears
• const every new line of constant declaration will make iota count once

//iota
const (
	a1 = iota //0
	a2        //1
	a3        //2
)

func main() {
    
    
	//pi = 123
	fmt.Println("n1:", n1)
	fmt.Println("n2:", n2)
	fmt.Println("n3:", n3)

	fmt.Println("a1:", a1)
	fmt.Println("a2:", a2)
	fmt.Println("a3:", a3)
}

The iota function is similar to enumeration.

define order of magnitude

//定义数量级
const (
	_  = iota
	KB = 1 << (10 * iota)//1024
	MB = 1 << (10 * iota)
	GB = 1 << (10 * iota)
	TB = 1 << (10 * iota)
	PB = 1 << (10 * iota)
)