Confused by Question #147 about cppquiz

[knatten]

I suggest we simply un-publish this question. It was created pre-C++17 when trigraphs were still a thing. Then it got ported to C++17 with the rest of the questions on the site, but I think it should have been unpublished instead since it no longer makes much sense. Any objections?

[nintendoeats]

That's neat, and I'm happy to know about it, but here's the thought process I went through (which I'd think is the same for most users):

1. I really really hope that this is 1.
2. But it couldn't possibly be 1. I mean, why would they ask?
3. There's this unusual comment, but it's just a comment.
4. Even the syntax highlighter agrees, that's just a comment
5. Well I give up, I'm entering 1.
6. 
7. So I'm right that this is 1.
8. And I'm right that that was just a comment.
9. So what I have learned was that there used to be a trigraph called ??/, but I don't know what it does and it's not actually relevant to the question I just answered.

Can you see why, coming at it from that perspective, the question just comes across as very strange?

I think what it comes down to is, if you knew what this trigraph was and what it did then this question is about "did you know this was removed in C++17". But if you don't (which I think is pretty common, given that it was removed), the question is "can you read code", and the answer description says "there's also a thing here which does nothing and is ignored".

Perhaps the solution is to add something like this to the explanation:

Prior to C++17, the ??/ was parsed by the preprocessor as being equivalent to the character \. Thus, the next line with x = 1; would have been treated as part of a multiline comment rather than as executable code. Therefore the output would have been 0 in older versions of the standard.
You can reenable this behavior in GCC using the -trigraphs option, or by specifying -std=c++14.

In addition, this is marked as level 3 difficulty. Makes it more confusing, since unless you know a piece of esotera this appears to be one of the most straightforward programs one could possibly write.

[tocic]

Please look at the compiler explorer link given in the answer. You can add the -trigraphs option to see the difference (it will compile, but the result will be different).

[tocic]

I agree that we should expand the explanation. @knatten take a look please

[knatten]

The question has now been retracted: https://cppquiz.org/quiz/question/147