Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Why do arrays start at 0?

buttondown.email

Post reply on HN
Print view View original

111–120 of 702 posts

Re: Why do arrays start at 0?

#111

Post by dllthomas »

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)…

But I think that still leaves open the question of "offset from what?"

If you move zero from the first element, you're still at the first element... but if you move zero from the fourth element you're still at the fourth element. If you move one from before the first element, you're at the first element.

I think you're more or less right, but I think we still need something to motivate the first element as the point of reference, and the machine focus is one way to do that.

Re: Why do arrays start at 0?

#112

Post by copperx »

dylan604 wrote: post #91
themacks wrote: post #49

Earlier quoted context omitted.

Typical counting of things starts from 0. If you count apples you implicitly start at zero and add 1 for each apple. If you count age, you start at birth (0) and count years; one for each birthday. That isn't zero based. The difference is the index of the item between the starting point and the next item. In zero based this item is number 0, in one based, this item is number 1. The first year of life is generally con…

>If you count age, you start at birth (0) and count years; one for each birthday. nitpick: unless you were born on Feb 29.

I didn't know that. Do you get to be 1 year old if you are born on Feb 29, to account for leap years?

Re: Why do arrays start at 0?

#113

Post by anamexis »

snarfy wrote: post #88
nomel wrote: post #66

Earlier quoted context omitted.

Arrays in the programming languages you’re familiar with use offsets. Not all do [1]. 1. https://therenegadecoder.com/code/which-programming-language...

Of course, and I've used Lua for a long time. The point is that offsets and indexes have different meaning.

Where are you getting this definition of index?

Re: Why do arrays start at 0?

#114

Post by copperx »

co_dh wrote: post #106
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…

Human makes a lot of inconsistent thing: We usually think the 1st floor, and the basement as 1st underground floor ( -1), but the floor jumps from 1 to -1! Also, the time jump from 11AM to 12PM to 1PM! So I think more human friendly sometimes means more confusing.

It's like English pronunciation, there's little logic. I gave up finding logic in these things at an early age, and resorted to memorizing everything instead.

Re: Why do arrays start at 0?

#115

Post by LudwigNagasena »

pb7 wrote: post #97
lupire wrote: post #94

Earlier quoted context omitted.

"ordinal" is preferred to "index", as "index" doesn't naturally suggest starting at "1", or even restricting the key to integers. "Ordinal" starts from 1, everyone agrees (except mathematicians, of course :-) ).

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.

Re: Why do arrays start at 0?

#116

Post by galangalalgol »

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.)

Doesn't Korea use the same new year as China? Usually second new moon after winter solstice.

Re: Why do arrays start at 0?

#117

Post by pavon »

AndrewOMartin wrote: post #78

"Should array indices start at 0 or 1? My compromise of 0.5 was rejected without, I thought, proper consideration." -- Stan Kelly-Bootle

This comes up when giving fractional coordinates into a grid. Is (1,1) the upper-left corner of the upper-left grid box, the center, or the lower-right (or the center of the next grid box)? Alternately, is the upper-left corner of the upper-left grid box (-0.5, -0.5), (0.0, 0.0), (0.5, 0.5), or (1.0, 1.0). I've seen all four conventions used in different places, depending on whether the grid boxes themselves are numbered starting at 0 or 1, and when extended to fractional if it makes more sense to have the corner or the center of the grid box take the value of the box itself.

Re: Why do arrays start at 0?

#118

Post by tda »

gnufx wrote: post #70
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...

As the article implies, Dijkstra was specifically wrong about FORTRAN, as defined at the time — the '77 standard, when it was still only conscionable to SHOUT 6 alphamerics. “… you probably know that arrogance in computer science is measured in nano-Dijkstras.” — Alan Kay

"This quote keeps on showing up out of context." — Alan Kay https://news.ycombinator.com/item?id=11799963

Re: Why do arrays start at 0?

#119

Post by jcelerier »

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…

At which number starts the first centimeter on a ruler ?

Re: Why do arrays start at 0?

#120

Post by bluetomcat »

twanvl wrote: post #45

Other advantages of zero based indexing, beyond being 'closer to the machine': It works better with the modulo operator: `array[i%length]` vs `array[(i+length-1)%length+1]`. Or you would have to define a modulo-like operator that maps ℕ to [1..n]. It works better if you have a multi-dimensional index, for example the pixels in an image. With 0 based indexing, pixel `(x,y)` is at `array[x+width y]`. With 1 based index…

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--) ...
Post reply on HN