Hidden features of C++
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I find it amazing that hidden gems exist like this in C++.
Coding for dyslexics:#include <QCoreApplication> #include <QDebug> #include <cstring> int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); // reverse indexing char str[] = "Hello World"; char str2[] = "Beano Could"; qInfo() << str; for(int i=0; i<strlen(str); ++i){ int i2 = strlen(str) - 1; i[str] = (i2-i)[str2]; } qInfo() << str; return a.exec(); }@fcarney said in Hidden features of C++:
I find it amazing that hidden gems exist like this in C++
Why do you find it amazing, and what's gemmy about it?
Have fun with it: https://godbolt.org/z/gPiYxP
The compiler just treats everything as pointer(s) and does the pointer addition as needed.Read and abide by the Qt Code of Conduct
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@fcarney said in Hidden features of C++:
I find it amazing that hidden gems exist like this in C++
Why do you find it amazing, and what's gemmy about it?
Have fun with it: https://godbolt.org/z/gPiYxP
The compiler just treats everything as pointer(s) and does the pointer addition as needed.@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.
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@kshegunov said in Hidden features of C++:
Ooh, that is a cool website. Assembler right in a browser. Thanks!
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@kshegunov said in Hidden features of C++:
Ooh, that is a cool website. Assembler right in a browser. Thanks!
The guy with the site: https://www.youtube.com/watch?v=bSkpMdDe4g4 (also a very good talk).
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If you want to have more fun: https://www.ioccc.org/years.html
For example: https://www.ioccc.org/2018/burton1/prog.nowarn.c -
Here is another interesting site:
http://madebyevan.com/obscure-cpp-features/ -
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 asstr[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 aboutinot being indexable....EDIT "I think the compiler should": maybe I meant "I expected the compiler to"....
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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.
C++ is a perfectly valid school of magic.
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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.
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@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.
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@fcarney said in Hidden features of C++:
digraphs
That's some bag-o-worms. My advice - don't dig there.
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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++.
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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++.
@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 :)
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@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 :)
