如何||和&&作品 [英] How || and && works

问题描述

main( ) {
    int   i = 4, j = -1, k = 0, w, x, y, z ;
    w = i || j || k ;
    x = i && j && k ;
    y = i || j && k ;
    z = i && j || k ;
    printf ( "\nw = %d x = %d y = %d z = %d", w, x, y, z ) ;
}

我只是在学习C，并且遇到了这段代码.老实说，我不知道w，x，y和z被分配了什么.显然，输出如下:

I'm just learning C and I came across this code. I honestly dont know what w, x, y and z are assigned to. Apparently the output is as follows:

w = 1 x = 0 y = 1 z = 1

"w"如何等于1?我不明白.

How is 'w' equal to 1? I dont get it.

推荐答案

|| 是逻辑或运算符.从C11 s6.5.14逻辑或运算符

|| is the logical OR operator. From C11 s6.5.14 Logical OR operator

||如果运算符之一比较，则运算符应产生1不等于0；否则，结果为0.结果的类型为int.

The || operator shall yield 1 if either of its operands compare unequal to 0; otherwise, it yields 0. The result has type int.

... ||操作员保证从左到右的评估；

...the || operator guarantees left-to-right evaluation;

将其应用于 w 的计算中

w = i || j || k  == (i || j) || k
                 == (non-zero || non-zero) || 0
                 == 1 || 0
                 == 1

x ， y ， z 的计算相似.C11 s6.5.13.3 声明&& 运算符的结果应为0或1.

Calculations for x, y, z are similar. C11 s6.5.13.3 states that the result from the && operator shall be 0 or 1.

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