const (

	countagn1 = 2 << iota // 2 0

	countagn2 = 2 << iota // 4 2

	countagn3 = 2 << iota // 8 6

)

// 00010 上面的计算结果：iota 不是递加然后加上常量值，而是递加位数，在常量值的二进制数位基础上左移

const (

	countagn4 = 3 << iota // 3 0  3*2^0

	countagn5 = 3 << iota // 6 1  3*2^1

	countagn6 = 3 << iota // 12 2 3*2^2

)

// 00011 所以，口算iota的计算结果，直接在iota的基础上乘以2的iota次方

func main(){

	fmt.Println("countagn1",countagn1)

	fmt.Println("countagn2",countagn2)

	fmt.Println("countagn3",countagn3)

	fmt.Println("countagn4",countagn4)

	fmt.Println("countagn5",countagn5)

	fmt.Println("countagn6",countagn6)

}

// OUT 

countagn1 2

countagn2 4

countagn3 8

countagn4 3

countagn5 6

countagn6 12