Hidden features of C++

[fcarney]

@kshegunov said in Hidden features of C++:

Why do you find it amazing, and what's gemmy about it?

Because its interesting and fun. It took a bit, but I found this explanation:

What square brackets really mean

Accessing an element of an array via ptr[3] is actually just short for *(ptr + 3). This can be equivalently written as *(3 + ptr) and therefore as 3[ptr], which turns out to be completely valid code. 

Once its explained it makes complete sense. I was imagining some operator overloading function juxtaposition of terms nonsense.

[fcarney]

@kshegunov said in Hidden features of C++:

https://godbolt.org/z/gPiYxP

Ooh, that is a cool website. Assembler right in a browser. Thanks!

[KroMignon]

@fcarney that's nothing special, it just simple pointer operation/arithmetic

@VRonin cool website, didn't know it!

[kshegunov]

The guy with the site: https://www.youtube.com/watch?v=bSkpMdDe4g4 (also a very good talk).

[VRonin]

If you want to have more fun: https://www.ioccc.org/years.html
For example: https://www.ioccc.org/2018/burton1/prog.nowarn.c

[fcarney]

Here is another interesting site:
http://madebyevan.com/obscure-cpp-features/

[JonB]

i[str] = (i2-i)[str2];

I'm going to throw this in here, and doubtless wait for others to disagree: I think the compiler should generate a warning on i[str]. Do I realize it's the same as str[i] --- yes, I do. Do I realize it's just the same as *(i + str), which I wouldn't complain about --- yes, I do. Bit I'd still like to see a friendly, 2019, open source compiler warning about i not being indexable....

EDIT "I think the compiler should": maybe I meant "I expected the compiler to"....

[fcarney]

@JonB said in Hidden features of C++:

doubtless wait for others to disagree

Or the obligatory "My <insert language> doesn't do this. That is why it is superior."
cough cough rust cough cough... ;)

(disclaimer: I have never programmed rust)

[fcarney]

Now I am kinda scared:

qInfo() << 3<:"Foobar"];

Outputs 'b'.
But this:

std::cout << 3<:"Foobar"];

Crashes

I am really struggling as to how that translates to an index in the first case, but crashes in the second case.

[fcarney]

@fcarney said in Hidden features of C++:

std::cout << 3<:"Foobar"];

Nevermind, it needs "\n" to output. It was crashing cause I was killing it... doh! I rarely use cout anymore.

[fcarney]

Also,
digraphs

Why? Why?!

[kshegunov]

@fcarney said in Hidden features of C++:

digraphs

That's some bag-o-worms. My advice - don't dig there.

[Kent-Dorfman]

I think the take-away from this discussion is that if you want to write code to really piss off someone else who has to read or maintain it then use C++.

[JonB]

@Kent-Dorfman
No, C++ readability/maintenance has nothing on this little gem language, which has always been a favorite of mine: https://en.wikipedia.org/wiki/Brainfuck. Here, for example, is Hello World! in its entirety:

++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>++.

And you can go to https://sange.fi/esoteric/brainfuck/impl/interp/i.html to paste it in and run :)

[ODБOï]

@JonB there is also Malbolge, but i don't thik this languages are designed to write real programs.

hello world

('&%:9]!~}|z2Vxwv-,POqponl$Hjig%eB@@>}=<M:9wv6WsU2T|nm-,jcL(I&%$#"
`CB]V?Tx<uVtT`Rpo3NlF.Jh++FdbCBA@?]!~|4XzyTT43Qsqq(Lnmkj"Fhg${z@>