iota和<<左移>>右移的用法

原创
2018/01/23 23:03
阅读数 277

    在go语言中iota比较特殊,是一个被编译器修改的常量,在每一个const关键字出现时被重置为0,然后在下一个const出现之前,每出现一次iota,其所代表的数字就会自动加1

    左移运算符”<<”是双目运算符。左移n位就是乘以2的n次方。 其功能把”<<”左边的运算数的各二进位全部左移若干位,由”<<”右边的数指定移动的位数,高位丢弃,低位补0。

    右移运算符”>>”是双目运算符。右移n位就是除以2的n次方。 其功能是把”>>”左边的运算数的各二进位全部右移若干位,”>>”右边的数指定移动的位数。

例一:

package iota

import "fmt"

func Test()  {

    const(
        c1 = iota  //c1=0
        c2 = iota  //c2=1
        c3 = iota  //c3=2
    )

    fmt.Println("c1 = ",c1," c2 = ",c2," c3 = ",c3,"\n")

    const(
        a = 1 << iota //a = 1
        b = 1 << iota //b = 2
        c = 1 << iota //c = 4
    )
    fmt.Println("a = ",a," b = ",b," c = ",c,"\n")

    const(
        v1 = iota //v1 = 0
        v2        //v2 = 1
        v3        //v3 = 2
    )
    fmt.Println("v1 = ",v1," v2 = ",v2," v3 = ",v3,"\n")

    const(
        x = 1 <<iota //x = 1
        y             //y = 2
        z             //z = 4
    )
    fmt.Println("x = ",x," y = ",y," z = ",z)
}

 

例二:

package main

import (
	"fmt"
)

func main() {
	const (
		a2 = 1 << iota   //iota = 0  a2 = 1 X 2的0次方
		b2 = 3 << iota   //iota = 1  b2 = 3 X 2的1次方
		c2               //iota = 2  c2 = 3 X 2的2次方
		d2               //iota = 3  d2 = 3 X 2的3次方
		e2 = 120 >> iota //iota = 4  e2 = 120 / 2的4次方
		f2               //iota = 5  f2 = 120 / 2的5次方
	)

	fmt.Println(a2, b2, c2, d2, e2, f2)
	//1 6 12 24 7 3
}

 

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