还是无效的C ++：为什么要编译此代码？ [英] or is not valid C++ : why does this code compile?

问题描述

这是我用QtCreator制作的一个非常简单的C ++应用程序：

Here is a very simple C++ application I made with QtCreator :

int main(int argc, char *argv[])
{
    int a = 1;
    int b = 2;

    if (a < 1 or b > 3)
    {
       return 1;
    }
    return 0;
}

对我来说，这不是有效的C ++，因为关键字或不是保留关键字。

To me, this is not valid C++, as the keyword or is not a reserved keyword.

但是如果我编译并运行它，它会在没有任何警告的情况下正常工作！退出代码为0，如果我更改b = 4，则退出代码为1！

But if I compile and run it, it works fine without any warnings ! The exit code is 0 and if I change b = 4, the exit code is 1 !

我不包含任何内容来确保没有隐藏的定义。

I'm not including anything to make sure there is no hidden define.

这对我来说真的很奇怪。这是Qt定义的吗？我没有在文档中找到与此相关的任何内容。

This is really strange to me. Is this something Qt is defining ? I didn't find anything in the documentation regarding that.

推荐答案

根据维基百科：

C ++定义了用作$$$ b运算符的符号的别名
的关键字：和（&&），bitand（&），
和_eq（& = ）或（||），bitor（|）或or_eq
（| =），xor（^），xor_eq（^ =），不是（！），
not_eq（！=），compl （〜）。

C++ defines keywords to act as aliases for a number of symbols that function as operators: and (&&), bitand (&), and_eq (&=), or (||), bitor (|), or_eq (|=), xor (^), xor_eq (^=), not (!), not_eq (!=), compl (~).

以 MadKeithV指出，这些替换来自C的iso646.h，并作为操作符关键字包含在ISO C ++中。 Wikipedia上有关iso646.h的文章说，这些关键字的确确实是用于国际和其他非QWERTY键盘，这些键盘可能无法轻松访问这些符号。

As MadKeithV points out, these replacements came from C's iso646.h, and were included in ISO C++ as operator keywords. The Wikipedia article for iso646.h says that the reason for these keywords was indeed for international and other non-QWERTY keyboards that might not have had easy access to the symbols.

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