C语言 赋值运算符

C语言的赋值运算符

​ 赋值运算符就是把表达式或者值赋给变量，比如极易混淆的=为赋值，等于是==。

​ 其实赋值运算符可以和很多前面说的算术运算符、逻辑运算符和按位运算符合并使用。

​ 如下如下：

赋值运算符	含义
=	赋值，等于
+=	加后赋值
-=	减后赋值
*=	乘后赋值
/=	除后赋值
%=	取模后赋值
&=	按位与后赋值
|=	按位或后赋值
^=	按位异或后赋值
<<=	按位左移后赋值
>>=	按位右移后赋值

举个例子来show一下：

/*advance/operator/operator2.c*/
#include <stdio.h>

int main()
{
    int a;
    printf("a is %d\n", a);
    a = 5; //0b101
    printf("a is %d\n", a);

    printf("%d += 2 -> %d \n", a, a += 2);
    a = 5; //0b101
    printf("%d -= 2 -> %d \n", a, a -= 2);
    a = 5; //0b101
    printf("%d *= 2 -> %d \n", a, a *= 2);
    a = 5; //0b101
    printf("%d /= 2 -> %d \n", a, a /= 2);
    a = 5; //0b101
    printf("%d %%= 2 -> %d \n", a, a %= 2);
    a = 5; //0b101
    printf("%d &= 2 -> %d \n", a, a &= 2);
    a = 5; //0b101
    printf("%d |= 2 -> %d \n", a, a |= 2);
    a = 5; //0b101
    printf("%d ^= 2 -> %d \n", a, a ^= 2);
    a = 5; //0b101
    printf("%d <<= 2 -> %d \n", a, a <<= 2);
    a = 5; //0b101
    printf("%d >>= 2 -> %d \n", a, a >>= 2);

    return 0;
}

相应地Makefile如下所示：

#advance/operator/Makefile

ALL : operator1  operator2

operator1: operator1.c
	gcc -o operator1 operator1.c

operator2: operator2.c
	gcc -o operator2 operator2.c

.PHONY : clean

clean:
	rm -f operator1 operator2

输入make，然后./operator2输出为：

a is 107106770
a is 5
5 += 2 -> 7
5 -= 2 -> 3
5 *= 2 -> 10
5 /= 2 -> 2
5 %= 2 -> 1
5 &= 2 -> 0
5 |= 2 -> 7
5 ^= 2 -> 7
5 <<= 2 -> 20
5 >>= 2 -> 1

可以看到结果就是对每一位进行的操作

那么问题来了，你知道为什么a刚开始的值是107106770吗，为什么每次都给a赋值吗？