Difference between “&&” and “and” operators [duplicate]

Question

This question already has an answer here:

• Is it okay to use “and”, “or” etc. instead of “&&”, “||”? 8 answers
• Should “not, and, or, not_eq..” be used in c++ 5 answers

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

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

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

Code :

#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";
   }
}

So my questions are:

• 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.)?

Answer 1

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

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.

Where and when do I use and over &&?

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.

why does C++ introduce alternative operators?

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 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`
 }
}

Answer 2

and, or, not, &c. are examples of the alternative operators.

For the full list see http://en.cppreference.com/w/cpp/language/operator_alternative; the opening paragraph is a raison d'etre:

C++ (and C) source code may be written in any non-ASCII 7-bit character set that includes the ISO 646:1983 invariant character set. However, several C++ operators and punctuators require characters that are outside of the ISO 646 codeset: {, }, [, ], #, \, ^, |, ~. To be able to use character encodings where some or all of these symbols do not exist (such as the German DIN 66003), C++ defines the following alternatives composed of ISO 646 compatible characters.

If I were you I'd shy away from using them, much in the same way as you ought to shy away from using digraphs and trigraphs, even if the latter make for interview fun.

Trigraphs for example are explicitly discontinued from C++17. You might see and &c. being dropped in future standards too.