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Why do arrays start at 0?

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Re: Why do arrays start at 0?

#191

Post by xxs »

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-...

the footnote [1] should be [0], just for the sake of this very topic.

Seriously though, while the idiom does work for unsigned integers, it's a bad idiom to learn [makes code reviews harder]. The post-decrement one in the loop body works with everything (signed/unsigned), and it's well known.

Re: Why do arrays start at 0?

#193

Post by bmacho »

kazinator wrote: post #55
atwood22 wrote: post #37

Earlier quoted context omitted.

No, we don't count from 0. That's like saying we start counting a baker's cup from 0 because you can have half a cup.

What do you do for a living, and why are they paying you not to understand this?

Can't they just .. disagree?

Birthdays are clearly 1 indexed, the first birthday is indexed with 1, and not with 0.

Re: Why do arrays start at 0?

#194

Post by drewzero1 »

randomdata wrote: post #19
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…

> when we count, we start at 1, we talk about the "1st" Although often with an implicit zero. Under typical North American culture, your 1st birthday, for example, is more accurately the first anniversary of your birthday. Your birth is zero indexed.

Oddly(?) though, most parents of young children don't refer to a baby as being "zero years old." Rather, we break them down into smaller units: two days old, six weeks old, four months old.

Re: Why do arrays start at 0?

#196

Post by 8note »

atwood22 wrote: post #148
kazinator wrote: post #58

Earlier quoted context omitted.

The counting activity doesn't begin when the first item is registered; it begins when the counter is initialized to zero. A decision is made to begin counting, along with the realization that nothing has been counting yet. That's when counting has started. When the first item is seen, the counting is then continuing. Suppose your job is to count some events. You check in for work at 8:00 a.m., but the first event has…

No, the mathematical definition of counting (i.e. whether or not a set is countable) involves mapping to the natural numbers, which doesn’t include 0.

Math counting doesn't care where you start. You could start -400 if it's useful for the problem

Re: Why do arrays start at 0?

#197

Post by Octoth0rpe »

LudwigNagasena wrote: post #115
pb7 wrote: post #97

Earlier quoted context omitted.

Ask 100 random people on the street and I'd be surprised if even 1 knew the definition of "ordinal". It's an uncommon word.

Do people not study grammar in American schools? I thought all kids learn the distinction between cardinal (one, two, three) and ordinal (first, second, third) numbers.

The English grammar that Americans study in school is likely somewhat different than the English grammar that is taught outside of America as the goal of the latter is likely focused on helping students map their native language onto English. I would agree that `ordinal` is uncommon word for many Americans, but it wouldn't at all surprise me if there were languages where the equivalent word was far more common, and therefore its use and translation was a part of standard English as a second language curriculum.

Re: Why do arrays start at 0?

#199

Post by perlgeek »

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…

A big international corporation (Siemens) had, at one point, standardized their buildings world wide to have room numbers starting with 2 on the ground floor, 3 on the floor above etc., leaving space for two basements.

All room numbers were 5 digits, and skipped numbers if there were multiple windows in one room, based on the theory that such a room might later be sub-divided, and wanting to avoid renumbering of rooms down the hallway.

(I encountered this around 2003, so might have well changed since then; didn't find any references only with a quick search).

Re: Why do arrays start at 0?

#200

Post by 8note »

atwood22 wrote: post #37
randomdata wrote: post #29

Earlier quoted context omitted.

The moment you are born you are 0 years old (or perhaps 0.75 years old, but we don't usually recognize that). We count from zero in this case, at least implicitly. In some cultures you are considered 1 the moment you are born, so the zero indexing isn't universal here, but typical in North America as noted earlier.

No, we don't count from 0. That's like saying we start counting a baker's cup from 0 because you can have half a cup.

I start with a empty cup, then I fill it up to 1 cup.

I then put it in an initially empty bowl

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