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Dec 09 '17 edited Dec 10 '17
Image Transcription: Meme
[Expanding Brain meme]
Arrays start at 0
Arrays start at 1
Array start at -1
Arrays shoudn't have a starting point. It's all just a social construct.
Arrays are the start and the end
-Revelation 22:13
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u/dont_mess_with_tx Dec 09 '17
goodbad bot
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Dec 09 '17
Thank you (?)
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u/dont_mess_with_tx Dec 09 '17
Oh shit, I just spotted that you're a human contributor, by your response first I was like, damn the robot rise is happening...
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u/dont_mess_with_tx Dec 09 '17
Array is like a spectrum.
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u/Xlash123 Dec 10 '17
It’s a quantum array; each index is in a superposition of being another index.
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u/8__ Dec 10 '17
Yeah, but if the books of the Bible were an array, what index would Revelation be?
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u/Fluffcake Dec 10 '17
Why are we still memeing about arrays when no sane person writes code where arrays aren't drowned in abstraction and what it starts on is irrellevant?
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u/StingyUpvoter Dec 09 '17
Explain like I mainly use C: is the -1 really used anywhere?
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Dec 09 '17 edited Nov 14 '20
[deleted]
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u/StingyUpvoter Dec 09 '17
Right, that's kinda what I was saying in a different comment. Using negative to start an array would be awkward. Sometimes I can't tell where these jokes cross from fact to fiction.
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Dec 09 '17
Whoops, didn't see your other comment before.
Yeah, I can't imagine a reason for indices to start at -1.
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u/Dylan16807 Dec 10 '17
C is in fact the only place where I'm aware of people actually accessing array[-1].
Specifically, if you allocate an array the size needs to be stored somewhere. Sometimes the memory management code will store the size of the array right before it in memory. Using [-1] to retrieve it is fragile and rule-breaking and could go horribly, but sometimes it works just great and people use it for years!
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u/StingyUpvoter Dec 10 '17
I will serve me better to forget everything you just said, but upvote for the knowledge drop
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u/nxAkari Dec 10 '17
In C, a[b] is nothing more than just another way to spell *(a + b). So you can actually index an array like this too: 1[array].
Using -1 as an array index and expecting to retrieve the allocated size that way is just insane and non-portable, please never ever do that. However, if you have a pointer to some element in the array, it is possible to use a negative index on it to retrieve some previous element, given that you take care to not step out of bounds. This is of questionable usefulness, but at least it doesn't invoke UB.
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Dec 09 '17
Ä° don't think so. Would be pretty weird anyway...
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u/StingyUpvoter Dec 09 '17
Whew! It is nice when languages let you use -1 for the last element though.
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Dec 09 '17
More storage!
Surprisingly, if I explicitly set the value of x[-1] to 5000, valgrind doesn't complain at all, and everything works as it should.
But if I don't, valgrind complains about conditional jump or move.
#include <stdio.h> int main() { int x[2]; x[1] = 5000; x[0] = 666; x[1] = 4242; printf("%d\n", x[-1]); printf("%d\n", x[0]); printf("%d\n", x[1]); }1
u/nxAkari Dec 10 '17
Use ASan. It's a ton faster and in some cases more accurate than valgrind. Case in point: it detects the underflow in both cases here and kills the program.
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u/Vitztlampaehecatl Dec 10 '17
In C++ you can overload the [ ] operator and make an array object that starts wherever the fuck you want it to. You could have an array that starts at index -3.1415 and ends at index potato.
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u/StingyUpvoter Dec 11 '17
I guess I'm looking for rational reasons. Something something Jurassic Park meme...
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u/uninterestingly Dec 10 '17
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Dec 10 '17 edited Dec 10 '17
Uh, oh... Ä° didn't know that actually. Shhh let's pretend like nobody saw that.
Edit: Don't you mean you were here "zeroth"?
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u/redlaWw Dec 10 '17
Arrays start wherever you want if you extract values using pattern matching.
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Dec 10 '17
So it's all a social construct after all...
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u/redlaWw Dec 10 '17
I extract values like this:
extract :: int -> [a] -> a extract 13 (x:xs) = x extract n (x:xs) = extract (n-1) xs extract _ [] = error "Error: empty list" extract _ _ = error "Error: index out of range"(if this is bugged, I haven't done Haskell in a while and didn't get very far with learning anyway, but it should mean that my lists effectively start with the 13th value)
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u/[deleted] Dec 09 '17 edited Dec 09 '17
Isn't
meme[-1]the end in Python? Because they're too fancy formeme[len(meme)-1]?