表达“变量，变量＝值；”。 [英] Expression "variable, variable = value;"

问题描述

我一直在浏览一些MFC代码，并且遇到了这个表达式。它在OnInitDialog（）函数中，看起来好像不是MFC特有的。变量有一个名字，值为0。

I have been looking through some MFC code and i came across this expression. It was in OnInitDialog() function, didn't look like it's MFC specific. The variables had some name, value was 0.

int volatile something, somethingElse; //this was global

something, somethingElse = 0; //this was inside the function

内部

在C ++中有意义吗？我知道逗号运算符是如何工作的，尽管它像这样的自由形式应该分隔表达式。变量名也是表达式吗？这段代码可以编译，因此它如何工作？

Does this make any sense in C++? I know how the comma operator works, though in a free form like here it should be separating expressions. Is a variable name also an expression? This code does compile, so how does this work?

推荐答案

这很可能是程序错误。语句

This is likely an error in the program. The statement

a, b = c;

完全等于

b = c;

由于逗号运算符从左到右求值，并丢弃除最后一个值以外的所有值。由于表达式a没有任何副作用，因此它基本上是无操作的。

Since the comma operator evaluates from left to right and discards all values except the last. Since the expression a has no side effects, it's essentially a no-op.

我会怀疑这是程序员错误还是来自其他语言的错误代码翻译进入C ++。您应该联系作者以使他们知道这一点。

I would suspect that this is either programmer error or an incorrect translation of code from a different language into C++. You should contact the author to let them know about this.

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