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Why do arrays start at 0?

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Re: Why do arrays start at 0?

#371

Post by salawat »

mananaysiempre wrote: post #165
bluetomcat wrote: post #120

Earlier quoted context omitted.

A disadvantage comes to mind. While the following loop works as expected: for (size_t i = 0; i The following causes an unsigned integer underflow and is an infinite loop: for (size_t i = length - 1; i >= 0; i--) ...

As Jens Gustedt points out[1], the following intentional unsigned overflow works perfectly for downwards iteration (even when length is 0 or SIZE_MAX), though it looks a bit confusing at first: for (size_t i = length - 1; i You are also free to start at any other (not necessarily in-bounds) index, just like with ascending iteration. [1] https://gustedt.wordpress.com/2013/07/15/a-praise-of-size_t-...

Principle of least surprise violated.

Also, that behavior is not guaranteed. The programmer would need to be aware of how the particular machine in question actually handles that.

Then again, that's C.

Re: Why do arrays start at 0?

#372

Post by TillE »

just_boost_it wrote: post #324
blueflow wrote: post #269

Earlier quoted context omitted.

That so people in this thread argue about the higher-level language (missing the point) shows that few people found access to the underlying machine code. Which is sad, because all code is still executed as machine instructions even when the developer does not see it or does not want to care.

We're 20 years past the point where you can expect everyone in tech to trace every instruction down to machine instructions. Higher level languages abstract away the need for it, and for the most part, we can rely on the authors of those languages to make many of the decisions that impact performance. The rest of us learn about these details on posts like this. It's not a sad fact, in fact it's probably one of the mo…

I barely touch assembly in my day to day work, but I do understand on a fairly deep level how a computer works, which I feel is extremely important and very frequently influences how I write high-level code.

Certainly one can bang out code their entire career without ever having a clue how machine code works, but I really wouldn't advise it. At worst it leads to total ignorance, and at best you accumulate a disconnected set of "best practices" as inscrutable lore handed down from on high.

Re: Why do arrays start at 0?

#373

Post by Koshkin »

oboes wrote: post #201
jaapsen01 wrote: post #27

Edsger Dijkstra wrote an interesting article titled 'why numbering should start at 0'. Perhaps not answering the question directly but an interesting read nonetheless. https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/E...

Interestingly, that Dijkstra article was originally published/circulated in handwritten form. It helps showcase the author's handwriting skills. https://www.cs.utexas.edu/users/EWD/ewd08xx/EWD831.PDF

The handwriting skills were common back in the day... By the way, are you sure that it was Dijkstra himself who handprinted these texts (rather than have, say, his secretary do that)? Because this is not exactly the (beautiful) handwriting as it was taught back then.

Re: Why do arrays start at 0?

#374

Post by v-yadli »

gnulinux wrote: post #279
v-yadli wrote: post #22

I'm fine with 0-based, 1-based or anything-based arrays (I recall it being convenient solving 8queen with pascal), but for Rage-Over-A-Lost-Penny sake, music note intervals are always beyond my understanding. Same pitched notes are called "interval 1" and there goes thirds, fifths, sevenths... All off-by-one in my base-offset-addressing mind... And then major vs. minor which creates all kinds of "aliased addresses"..…

You do understand that besides thirds, fifths and sevenths, there really are seconds, fourths, sixths, ninths (same as second), elevenths (same as fourth) etc... as well, right? There even are intervals that are not named after a number e.g. the "tritone". The reason the 2nd and the 3rd note in a chord are called third and fifth is because usually chords are made with these intervals instead of dissonant intervals li…

It's that off-by-one nature of intervals that always bumps me. The difference between note a and b is (a-b+1). Calling an octave "an octave" feels to me like calling a numeric system with digits 0x0-0xf as "base 17"

Re: Why do arrays start at 0?

#376

Post by kccqzy »

numlock86 wrote: post #35
hougaard wrote: post #14

It really comes down to a choice between a machine-focused (0) or human-focused (1) approach. The 0 makes a lot of sense in a C pointer world where memcpy and other alike functions can be written very thight. The 1 makes a lot of sense in a human world, when we count, we start at 1, we talk about the "1st", counting on finger starts with 1, etc. I once were at a Lua (1 indexed language) conference where this was disc…

> It really comes down to a choice between a machine-focused (0) or human-focused (1) approach. Just think of 0-based as offset-based and 1-based as index-based. Both are intuitive just like that. I never get why people arguing over this bring pointers and memory (or anything computer related) to the table. No normal person is going to understand that, but everyone understands that if you don't move at all (0 offset)…

I must say in this case Google does it right: https://cloud.google.com/spanner/docs/reference/standard-sql...

In Google standard SQL, to access an array it is simply not allowed to put a number inside square brackets. You must specify which way you mean. So `SELECT some_numbers[OFFSET(1)], some_numbers[ORDINAL(1)]` is allowed but not `SELECT some_numbers[1]`.

Re: Why do arrays start at 0?

#377

Post by GnarfGnarf »

bregma wrote: post #168

If you ask people which floor of building they're on, it's going to depend on which country they're in. In North America, at least, the first floor you walk into (in a sane city: I understand there are some which do not qualify in this respect due to hills or historic disaster recovery) is the first floor. On other continents, you enter the ground floor and need to take stairs or an elevating device to get to the fir…

The Patterson Building at Acadia University in Wolfville, NS, has a basement and four floors. The rooms on the first floor are numbered 1XX, second floor 2XX, etc. up to the top floor 4XX.

The elevator, however, goes from floor '1' (the basement), to floor '5' (the top or fourth floor).

This really confuses visitors.

The Elevator Mafia want $10,000 to fix it.

Re: Why do arrays start at 0?

#378

Post by TOGoS »

anigbrowl wrote: post #311
divbzero wrote: post #283

Earlier quoted context omitted.

The same applies to counting in other bases too. For instance, in 1-indexed counting grids for kids, the last column always feels out of place. 0-indexed decimal grid: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 8…

Are you sure it doesn't just look that way because you are used to monospaced fonts? Ask a kid to show you their zeroth finger.

As a kid, I saw these things often on multiple-choice test sheets. The tens digit at the end of each row not matching that at the beginning always seemed awkward, and I wondered why they didn't just start at zero. This was long before I did any programming.

The first year CE being "1" resulting in the new millennium starting at 2001 instead of 2000 also seemed idiotic, and the 1900s being referred to as "the 20th century" was something I always had to consciously compensate for. Numbering items starting at zero would have given us more elegant/less confusing ways to communicate those things.

Zero-based indexing makes things inherently simpler because it matches the way we write numbers (and becomes much more noticeable once you have more than one digit). It's not just an optimization for computers.

Re: Why do arrays start at 0?

#379

Post by thwarted »

If your arrays start at 0, you have offsets.

If your arrays start at 1, you have indexes.

"0-indexed" shouldn't be a thing. I like the screenshot quote that refers to this as either "1-origin" or "0-origin".

Re: Why do arrays start at 0?

#380

Post by [deleted] »

jefftk wrote: post #361
Jtsummers wrote: post #320

Earlier quoted context omitted.

https://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/source/... Convenience. Look at how the days in the months are stored and accessed. Using 1-based months would introduce an extra calculation (-1) on all searches or an unused value in the 0-index. Also look at how printing is handled for weekday and month names. They, again, take advantage of 0-based indexing. Day and year are already represented as numbers, so it…

Subtracting 1 from the user provided index isn't that expensive. Or, if you're willing to give up three bytes, index into "ErrSunMonTueWedThuFriSat". Or, and this is mildly insane but perhaps in keeping with early C, have your pointer be three bytes before the beginning of "SunMonTueWedThuFriSat" and use one-based indexing.

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