Why do arrays start at 0?

Post by BeFlatXIII » Wed, Aug 24, 2022, 8:00 PM UTC

yongjik wrote: post #95

randomdata wrote: post #19

Earlier quoted context omitted.

> 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.

That's why I prefer the Superior(TM) Korean age counting. You are one year old when you're born (it's your first year!). You are two year old on the next New Year's day. (Congratulations, it's your second your now!) So, if you're born on December 31st, you're two years old the next day. (I see no problem, but apparently some people are hung up on such minor details. I can't fathom why.)

Post by divbzero » Wed, Aug 24, 2022, 8:00 PM UTC

diego_sandoval wrote: post #273

Because otherwise you would be wasting a perfectly good number for no reason, which means you need to use more bits to do the same thing. To write 4 numbers (including zero) you only need two bits 0: 00 1: 01 2: 10 3: 11 To write 4 numbers if you avoid using the number zero, you need three bits 1: 001 2: 010 3: 011 4: 100 If you extrapolate that a little bit, you'll realize that you'll need two bytes (1 Byte + 1 bit…

   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 87 88 89
  90 91 92 93 94 95 96 97 98 99

  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 87 88 89  90
 91 92 93 94 95 96 97 98 99 100

Post by layer8 » Wed, Aug 24, 2022, 8:01 PM UTC

intrepidhero wrote: post #226

hcrisp wrote: post #40

Dijkstra's answer (linked in the article) is best: "When dealing with a sequence of length N, the elements of which we wish to distinguish by subscript, the next vexing question is what subscript value to assign to its starting element. Adhering to convention a) yields, when starting with subscript 1, the subscript range 1 ≤ i https://www.cs.utexas.edu/users/EWD/transcriptions/EWD08xx/E...

It could just as easily be 1 ≤ i ≤ N and then I wouldn't have to remember that the lower bound is inclusive and the upper exclusive.

Post by msk-lywenn » Wed, Aug 24, 2022, 8:03 PM UTC

empiricus wrote: post #262

xxs wrote: post #137

Earlier quoted context omitted.

the correct way/idiom to reverse iterate an array is for (size_t i = length; i-- > 0; )... It's surprising how often the issue pops, it works well with both signed and unsigned integers. (edit) I've started with one based indexing (basic)... mixed with 0 based (assembly), more 1 based (pascal), then more stuff (all zero based). I am, yet, to see a real advantage of a one based indexing... after the initial process.

Is this cache friendly?

Post by naavis » Wed, Aug 24, 2022, 8:03 PM UTC

411111111111111 wrote: post #277

mananaysiempre wrote: post #165

Earlier quoted context omitted.

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-...

Uh I'm confused but don't know c++. why doesn't that loop end instantly? I mean length - 1 Or does it only terminate when the number underflows? Terribly confused here