C ++ if语句符号-这等效吗? [英] C++ if statement notation - Is this equivalent?

问题描述

我99％的人肯定这行不通，但剩下的1％的人困扰我

I'm 99% sure this won't work but that remaining 1% is bothering me

    int x;

    //is this if statement

    if(x == 1, 5, 7)
    {
    //do something here
    }
    //equivalent to this if statement

    if((x == 1) || (x == 5) || (x == 7))
    {
    //do something here
    }

推荐答案

不，这完全不等效.

if(x == 1, 5, 7)

调用逗号运算符，由于优先级最低:

calls the comma operator, which will effectively end up in the last value because of , has the lowest precedence:

if(7)

因为带有括号的展开应该看起来像

since unfolding with parenthesis should look like

if(((x == 1), 5), 7)

同时

if((x == 1) || (x == 2) || (x == 7))

检查x是否等于1，2或7.

这篇关于C ++ if语句符号-这等效吗?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！