“&&"和“&&"之间的区别和“和"经营者 [英] Difference between "&&" and "and" operators

问题描述

我看到了替代运算符(例如and，or， not等)浏览cppreference时.

I saw alternative operators (like and, or, not etc.) when browsing cppreference.

它们是&&，||，!等常规"运算符的替代方案.

They are alternatives to "normal" operators like &&, ||, ! etc.

我检查了汇编中是否使用了&&和and的代码.两个版本都生成相同的程序集.

I examined the assembly for code that uses && and and. Both versions generated the same assembly.

代码:

#include <iostream> 

int n = 1;
int main()
{
// if(n > 0 && n < 5)
   if(n > 0 and n < 5)
   {
       std::cout << "n is small and positive\n";
   }
}

所以我的问题是:

• &&和and运算符有什么区别?
• 我何时何地在&&上使用and?
• 如果没有区别，那么C ++为什么引入替代运算符(例如and，or，not等)?

• What is the difference between the && and and operators?
• Where and when do I use and over &&?
• If there is no difference, then why does C++ introduce alternative operators (like and, or, not etc.)?

推荐答案

&&和之间的区别是什么?和和运算符?

What is the difference between the && and and operators?

没有 ¹ .这些运算符的替代"方面意味着，从语义的角度来看，它们可以用于构造完全相同的表达式.

There is none¹. The "alternative" aspect of these operators means that they can be used to construct the exact same expressions from a semantic perspective.

我在何时何地使用&&&?

Where and when do I use and over &&?

这在很大程度上是一个优先事项.我已经习惯了&&不使用它，但是可以理解是否有人发现and更具可读性.

This is largely a matter of preference. I'm too used to && to not use it, but can understand if someone finds and more readable.

为什么C ++引入了替代运算符?

why does C++ introduce alternative operators?

C ++被设计为可在各种字符集和平台上使用.象Bathsheba指出的那样，三部曲是这种功能的另一个例子.如果一个字符集不允许写入&&(例如，因为它根本没有&字符)，那么仍然可以使用其他表示形式.如今，这在很大程度上尚无定论.

C++ was designed to be available on a variety of character sets and platforms. Trigraphs, like Bathsheba pointed out, are another example of such a feature. If a character set would not allow && to be written (say, because it simply didn't have the & character) then one can still get by with the alternative representation. Nowadays, it's largely moot.

_{¹ 实际上，经过进一步的思考，我对第一个问题的回答可以得到完善.关于令牌的解析方式，稍有不足. &&不需要将空间解析为单独的标记，而and则需要.这意味着:}

_{¹ Actually, upon further thinking, my answer to your first question can be refined. There is a slight lack of equivalence, pertaining to how tokens are parsed. && doesn't require a space to be parsed as a separate token, while and does. That means:}

void foo(bool b1, bool b2) {
  if(b1&&b2) { // Well formed
  }

  if(b1andb2) { // ill formed, needs spaces around `and`
 }
}

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