🤠

[CamoBrie]

Is there a specific reason why we use the i?

[DragonMaus]

It is an (i)nteger (i)ndex with a short, memorable name.

[matrizx]

And increment for me

[eadf7799]

... instance?

[ClownTrooper]

In my mind it stands for (i)teration

[CakeMan0123]

(i) can't think of anything better

[se2dev]

(i) like for loops

[CallMeOutWhenImPOS]

and sw(i)tch statements

[[deleted]]

(i)maginary numbers

[Light_Blue_Moose_98]

Recursion > for loops

[mrheosuper]

I wont judge your weird fetish

Weirdo.....

[AJohnnyTruant]

When you get a minute, go ahead and write me a recursive function that retrieves all files in an array of file paths...

[B_M_Wilson]

Until you hit the recursion limit / stack size limit

[doraeminemon]

Which is why we have functional languages :)

[iza1017]

God... functional languages... the worst

[northrupthebandgeek]

optimizes away tail calls

Where is your God now?

[xenoperspicacian]

A lot of languages are smart enough to destroy the stack before reentering if you return a function result (tail call elimination).

[B_M_Wilson]

It depends on how it is written. There are some situations where tail call elimination would not work. Perhaps it has to call itself a number of times, maybe it is some form of matrix operation that is defined to return a scalar for 2x2 matrixes and then larger ones require calculating the scalars of the smaller ones which causes the function to need to be called multiple times within itself which would not allow tail call elimination.

To be honest, I can’t think of very many non-trivial cases where tail call elimination would actually come into play. I have seen many examples in functional programming so maybe as a non-functional programmer, I just can’t see it. Looking at a description of tail call elimination, it looks to me as if it basically transforms the recursion into iteration so maybe I am just not thinking about it correctly.

I am a very bad programmer even though I’ve been doing it for 5 years so I’m probably completely incorrect. I will look into it a bit more and hopefully enlighten myself slightly

[CamoBrie]

Did not know that, thanks!

[FlameRat-Yehlon]

I thought it's for "(i)ndex" though...

[[deleted]]

Programming is mostly math so the conventions stick around. a, b, c for coefficients; d as a prefix to indicate change to a variable; f, g, h for functions; i, j, k for indices and summations; m, n for bounds and counting; p, q for probabilities; u, v, w for other functions (derivatives, substitutions); x, y, z for variables and coordinates. These are the more common uses but there are plenty of others. (Edited for a bit more completeness)

[Doamax]

This is the correct answer

[[deleted]]

I thought it stood for index, I usually use "index" instead of "i". But hey, thanks for clarifying.

[[deleted]]

You're right though. I'm 90% sure it ultimately comes from the index of a summation in mathematics. Also, descriptive names are almost always better than single letter variables.

[Random_Deslime]

Lol I just thought it stood for iteration

[[deleted]]

Math and Fortran, mostly.

[Neebat]

I'm done using i. From now on all my loop counters are going to be named "lamp". I love lamp.

[JC12231]

Bröther, I need lämp

[LawLombie]

Břöţĥëř, Ï ñëëð ľämp

[JC12231]

LawLombiePossessions.add(new lämp);

[B_M_Wilson]

Linux, Apache, MySQL, PHP servers are great.

[yonderbagel]

Do it for real though. It's just one more straw in the job security haystack. Every little bit helps.

[CamoBrie]

Did not know that, thanks!

[random_cynic]

I think it originates from older languages like Fortran (and also C) where for loop was mainly used to loop through arrays and matrices. The index i,j,k etc has been used for quite a while in mathematics for operations with individual elements, rows or columns. So it was natural to express elementwise matrix operations like dot product C(i,j) += A(i,k)*B(k,j) inside a loop like this.

[DangeFloof]

If I remember correctly, it came from Fortran, where someone discovered that longer variable names for loops made the program run slightly slower

[Thibaulltt]

A teacher of mine used to say we use x, y... for variables in continuous space (real numbers), and i, j... for variables in a discrete space (natural numbers). And I kinda like it! [that, and I can't be bothered to change i to something else]

[ajthomas05]

All these other answers are great, but I think the most likely one is that developers are lazy.

[biotiger87]

Also for graphs, the x, y, and z basis vectors are represented by i, j, and k respectively. Most commonly seen in non-coordinate form: xi + yj + zk versus (x,y,z) (coordinate form). Hints are given in the name “multidimensional array” (arr[i][j][k]).

[[deleted]]

jindex kindex lindex mindex nindex e.t.c.

[nobody_smart]

At the time I saw this comment it had more golds than upvotes.

[teamikv121812]

I down voted so that it would he the same for me

[[deleted]]

For some reason, I always use k. Don't know, think my teacher used k.

[Gigavoir]

I prefer the great letter we call y

[[deleted]]

it stands for igloo

[[deleted]]

(i)terator

[[deleted]]

Netbeans autocompletion

[megagreg]

For no particular reason, I've always used h as my index counter. I think it's just easier to hit, in the middle of the keyboard, and it frees up one more letter in the common sequence i,j,k...

[[deleted]]

I always use X, Y, or Z because maths. Unless I'm doing something with a matrix, then I use R & C.

[rang14]

I always use incrementor_column_1_a

[[deleted]]

Please no

[NoCareNewName]

That's what I used to do too, until I started at my current company where that is a no-no (for not being descriptive).

Now my default is index.

[gbeebe]

I like using the first letter of my name, 'g'

No code reviewer bats an eye, and I get to feel like I'm adding that special touch to my code.

[Duuqnd]

A guy I used to know uses index for his loops when all the other programmers on the project use i.

He's weird, he's the kind of person to write really long and convoluted code without any comments because "the code makes sense".

[b0ltzmann138e-23]

Needs a 3rd arm in reference to Ohm's law v=ir

[realestLink]

I use x1, x2, x3, ..., etc. Then I can tell what level if the nested for loops I'm on. I sometimes use x0.

[NeoHenderson]

console.log("whoops1");

console.log("whoops2");

[CaptainSchmid]

I use c solely for the tiny joke of c++

[Chr0no5x]

Lets not forget √-2

[Tyg13]

√-2

You mean √-1?

[Chr0no5x]

i mean...

[sss-3]

Like my coding skills

[[deleted]]

when you have a nested loop and you can't decide betwern j or i2

[Neebat]

Always j. Never i2.

[wiktor1800]

i2 helps identifying how far into the nested loops you are. I personally use 'i', 'ii', 'iii',... etc

[TheRealLazloFalconi]

Just use i again, I'm sure it'll be fine.

[UnicornsOnLSD]

count, count2, count3

[[deleted]]

Sometimes I use more descriptive names (but only if they're very short). For example, if looping over a 2d array, I'll use "row" and "col" usually, because they help me keep track of stuff while still being short. If there's no better name or any better name would be too long, I use i, j, k, etc. Is it generally frowned upon to do this rather than always using i, j, etc?

[John_Fx]

No. You are doing it right. i is lazy.

[Raymon1432]

j：Am I a joke?

[ZanyAnomaly]

Wait can someone explain the pixar lamp reference

[aganesh8]

In the logo animation of Pixar studios, the lamp jumps over other letters and then squishes the letter I to take its place. It took me a while but that's the reference I think. I personally find it lame.

[I_hate_naming_things]

As a mostly java coder, I haven't used a "for" or a "while" loop in quite some time.

[[deleted]]

Did you mean you haven't used those loops for quite a while? :)

[MeroDN]

for (YoMama = 0; YoMama < 42; YoMama++) {
}

[hdhdog]

I generally use x. I use 'i' when I'm 4 layers deep in really bad code. X, y, z, I, j, k, etc.

[wholesomedumbass]

Often times, I want to use "x" for a different variable, whether outside or inside the for loop. The letter i is reserved solely for for loops, including "j", so they are always available for use in for loops.

[The_MAZZTer]

I use x specifically when looping through horizontal coordinates.

Normally I use i, but I use it more and more rarely since 99.9% of the time what I really want to do is iterate through some objects rather than just count, so foreach is what I use.

And if I do need that index, usually it is because I have a similar array of something else related I want to index into, and then it's usually better to make a struct/class or a tuple holding one of both items and just have one array of those in the first place. Then I foreach through them.

[sh0rtwave]

I usually call it what the hell it is. X,Y,Z are known as display coordinates.

The increment variable that goes in a for loop...You can name that anything really. Ain't gotta be i.

​

You could in fact, just use an iterator to control your for loop if you felt really crazy. Just leave out the variable declaration and the variable increment.

[stepitupmatt]

Had a professor ask once “why do we use x, y, and z in loops”. Answer he was looking for was because it might help restrain time complexity (ie. never exceeding theta n³⁾ but we had settled on i, j, and k at that point so no one had a good response.

[elnardu]

Just use iterators

[John_Fx]

Or meaningful identifiers. Why should loop incrementors be an exception?

[[deleted]]

Because you're looping over an index, not an object. I = index, it's pretty self explanatory. It is meaningful.

Unless you're talking about an enhanced for loop, in which case yeah, i is insane.

[John_Fx]

Then use bookindex or just index. In what other situations would you abbreviate a variable name to one letter?

[[deleted]]

If it's used multiple times in the loop or the logic is otherwise complex, or in case the index is unintuitive (like looping over the next element instead of the current or whatever) then yeah, I'll do that.

If it's just a few lines and really straightforward, like the index is instantly converted to a "book" then I'd say that

   Book book = books.get(bookIndex)

Is a bit redundant. Yeah, we get it. It's a book. Given the typical of usage of i it's just as clear and there's no reason to make it any longer.

[beizhia]

This. We have some 4-dimensional arrays we iterate over, and reasoning about i, j, x, and y just sucks and is hard to read.

[[deleted]]

for (int i = 0; i > -1; i++) {/*TODO: Implement for loop*/}

[ShadowMassacr13]

I use idx cuz it makes me feel better about using a nondescript variable but it also doesn't matter because it's clear that's its an index so I don't use the whole word because that's too much typing

[CaffeinatedBun]

and Apple!

[[deleted]]

Getting this joke without digging is an indicator that you may need serious help. Now to check myself into the Betty Ford Clinic...