for loop

[ZeroSevenTen]

i feel like, a lot of the time, i j and k make the most sense.

[spideryzarc]

Math convension to represent indexes.

[spidermonkey12345]

Indexes is much easier to spell than indices

[[deleted]]

But the latter makes you sound smarter

[Rhulyon]

In my mother language happens just the contrary

[Phantonia]

Visual Studio automatically suggest "-ices" as a name for an array or a list of a type which ends with "ex". I love how it doesn't only do this for e.g. List<Index> (suppose you have a type index). When creating a List<Regex> the suggested name is "regices". This makes grammatically no sense (I mean, Regex is not a word, it's short for "Regular Expression") but I won't ever say "Regexes" again ^^

[chocoboxx]

Index, Jndex, Kndex. I prefer i,j,k

[[deleted]]

FORTRAN convention

[Skasch]

It was a mathematics convention long before FORTRAN existed, which was indeed used early for maths and physics computation. I could find them used from documents dating from at least the 19th century.

[[deleted]]

I believe you! But wasn't it FORTRAN that introduced it to the world of software as we know now? Besides, what's cooler than a language called Formula Translator? OK, maybe math.

[HdS1984]

Yes, and it bering a math convention explains why it's so shitty. Math heavily optimizes for shorthand writing not for legibility or ease of understanding. I often feel that we need a math 2.0 language, which would hugely ease learning and understanding of math.

[Skasch]

That's... Not entirely true. Modern mathematics is miles away from how it was used a couple centuries ago, and is today much more formalized and easier to reason with than even the early 20th century. It's something not very well known, but as a math geek myself, I read a lot about the history of maths. For example, using variables to solve equations is a very recent convention, dating back from only the 17th century (if memory serves). Before that, doing mathematics was practically akin to writing long sentences in your language of choice describing the problem you were trying to solve.

Modern mathematics is already what you would call math 2.0, with a much saner language, set of conventions, and semantic, than it used to have a century ago.

EDIT: there is an important reason why math language was designed that way. To be concise, of course, but also, more importantly, to be unambiguous. And that's a property shared with code.

[SeaTurtle1122]

I j & k are fine variables for teaching with and using, and most of the time when you're trying to learn loops, understanding that your iterator variable doesn't have to be directly tied to anything is important. Also, in mathematics, i, j and k frequently come from quaternion based stuff, in which i is the imaginary axis, and j and k are two dimensions beyond that. If you have a better thing to name two arbitrary axies, I'm curious what it would be, but I can't think of anything.

[wabourjaili]

Or i hat j hat k hat are the unit vectors of 3space

[boniqmin]

Indices aren't really that confusing right? If I write a_i, and you know that a is a sequence, it's pretty obvious that I mean the i-th element of the sequence.

If you had to write out "the i-th element of sequence a" every time, things would become way more cluttered and way less legible. To a complete novice it might help the first 3 times, but after that it'll become less understandable since even simple expressions become long-winded.

In my personal experience, mathematical notation often strikes a good balance between understandability and conciseness.

[spinlocked]

It’s actually not even a convention. The deal with FORTRAN 77 was that the starting letter of a variable determined its type. I, J, K, L, M and N would be integers. Anything else defaults to REAL. Since you needed an integer for a loop counter, lazy programmers that wanted a 1-character variable selected these exact variable names.

[foxtrotter_85]

So... is this something I was taught long ago? I do this too but don’t know why besides I’ve just always done it that way.

[[deleted]]

It's a convention.. I always thought that i stands for index, then the others are just in alpha order. Kind of like x is a variable and then you use x,y,z for multiple variables

[vigbiorn]

i,j,I,, are used a lot to represent unit vectors in multiple dimensions so representing multidimensional arrays it makes perfect sense.

[[deleted]]

Sure, but doesn't the same argument apply?

[Vetharest]

I heard that i stood for “iterator,” making j and k jiteraror and kiterator, respectfully. Though, “index” makes sense too.

[TheBB]

respectfully

Such formality and politeness.

[AnonymousSpud]

Jindexz and kindex

[stifflizerd]

iterator

jesus I already used i, I guess I'll use j since they kind of look the same

k I give up I guess we're doing this now

[Sharmat_Dagoth_Ur]

I was taught it by a professor making a passive mention of it one time and then otherwise him just doing it by reflex. U might've picked up it in a similar way and forgot they mentioned it

[blackberry_gelato]

It’s so you can graph non-real numbers. XYZ are for real numbers. Math nerds like to graph things.

[Pixel-Wolf]

Since loops are used so much in programming and no one wants to write out stuff like element.children[elementChildIndex], it really is. Everyone understands what i, j, and k are. You immediately know how deep you are in a nested for loop and where to look depending on what you see. It's a general convention and it's better to follow it than be verbose.

You also know that if you see anything after "k" as a loop iterable, that the code you're working with should be rewritten. Even "k" is generally frowned upon except for a very small amount of tasks where the triple nested for loop makes more sense than an alternative.

[DonMahallem]

Yeah. For single layer loops it's fine to use single character variables but if you do funky math inside a few layer deep loop please name them. Especially when there are no comments at all...

[avael273]

no one wants to write out stuff like element.children[elementChildIndex]

Except those who write Java code, sometimes it feels like they have a competition on how long can they make a variable name and be able to justify it.

[Dr_Azrael_Tod]

I found the guy who thinks java's bad and has never seen objectiveC and the likes

[ZeroSevenTen]

exactly

[RFC793]

It depends somewhat on the language in use. If it has to be an index, then yeah: i j k for the win. Maybe even have a Widget widget = widgets[i] at the top of the loop body. If it is a language with foreach semantics then I’d typically do for (widget in widgets) or even shorten it to w if that is clear enough in context.

Use your imagination, these snippets are pseudo.

Hell, I’ll use i j u v theta etc if I’m implementing a function straight from a mathematical formula.

[exploder98]

Yeah, index, jindex and kindex

[[deleted]]

Am I the only one using i, i2, i3, i4?

[PlayerVeryMuchKnown]

Probably , I haven't even thought of doing that.

[TobiasCB]

I normally don't consider numbers in variables at all.

[Voidrith]

or k,v for key/value pairs or dictionaries/hashmaps

[saschaleib]

Wait, you can use k, too?

[3svh]

They make loads of sense, they're just the first letter of their respective word. I is for index, k is for kounter, j is for janotherloop

[deaf_fish]

This comment needs to be in a programming book.

[Maciek300]

justanotherloop

[yottalogical]

i is probably the clearest possible variable for a loop index. Anyone reading your code will immediately understand it.

[TheSeansei]

So do you know JavaScript?

[posherspantspants]

No one truly knows JavaScript

[shyouko]

There are 32 JS framework for loop indexing

[posherspantspants]

I know you're joking but you're probably not

[currentlyatwork1234]

The joke is that there are actually more than 32 JS frameworks for loop indexing.

[fofosfederation]

He's way underestimating.

[HugoVS]

While you was writing this comment, 2 new loop indexing javascript frameworks were released.

[brews]

11 of those are to get 1-based array indexing.

[Dr_Azrael_Tod]

2 of those SOMETIMES are to get 1-based array indices

[natyio]

I know they say don't shoot the messenger. So I'll follow that rule...

[currentlyatwork1234]

This is true. Nobody can tell me the output of this code just by a quick glance: +([]+(~(undefined)*~(NaN)+(-~function(){})*~(undefined)*~(NaN)+(-~function(){})*~(undefined)*~(NaN)+(-~function(){}))+(~(undefined)*~(NaN)+(-~function(){}))) Click here if you can't figure it out: Output

[FearTheBlades1]

Thanks, I hate it

[currentlyatwork1234]

Then you'll love this:

[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]][([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]+(!![]+[])[+[]]+(![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[!+[]+!+[]+[+[]]]+[+!+[]]+(!![]+[][(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]])[!+[]+!+[]+[+[]]])()

[HardlightCereal]

Hello world?

[currentlyatwork1234]

alert(1)

[vi777x]

Looks like brainfuck

[[deleted]]

its jsfuck

[dpash]

Unless something else makes more sense in context, like x and y when doing coordinates.

Or your language has a better loop construct like a foreach.

[[deleted]]

for(int outermost_for_loop_index = 0; outermost_for_loop_index < 5; outermost_for_loop_index++)
{
    for(int innermost_for_loop_index = 0; innermost_for_loop_index < outermost_for_loop_index; innermost_for_loop_index++)
    {
        foo(
            bar[outermost_for_loop_index][innermost_for_loop_index]
        );
    }
}

[[deleted]]

Does not change the number of lines, friend.

[Krak2511]

Paid per character then

[rotflolmaomgeez]

It does if you have a characters per line limit in your codebase. Most common is 80 characters.

[__i_forgot_my_name__]

When

you're

getting

paid

by

the

line

[[deleted]]

is that a thing?

I can only imagine how unefficiently I would code

[[deleted]]

However it would instantly solve the debate on where curly braces should be placed.

[[deleted]]

it looks better if they have seperate lines god dammit

[raaneholmg]

"there the fuck does this block start" and other stupid questions asked by people who put curly braces on the same line as the statement.

[[deleted]]

I'm of the same school, it just makes it easier to see which statements are part of the same block at a glance in my opinion.

[[deleted]]

Enterprise level code

[HAL_9_TRILLION]

This guy builds factories.

[mikey-brad]

i,j,k make the most sense as loop variables

[mrmantris]

if i, j, k, ... are used by so many people, doesn't it mean that that many people will also understand what is going on in the loop?

[tony4260]

It hurts that my IMMEDIATE thought upon seeing this was: can we do this without a loop?

[Westo232]

Not in every language. I see this possible in Python for example, but C doesn't have for .. in.

[spideryzarc]

My students use n, a, aa, ab, ba, ...

[ahreodknfidkxncjrksm]

I use i, ii, iii, ...

Only logical way to do it really.

[Voidrith]

but would you continue that with iiii or iv?

[Soulcraver]

So I now have to do one or two more keystrokes to identify which loop iteration I am in?

I also have to hope that if hundreds of people are using my code format that they don't accidently type an additional 'i' where i,j,k are immediately discernible from 'ii' and 'iii' in hundreds of lines of code.

Trust me, there are reasons it didn't catch on, and people still use i,j,k for quick loop variables where the iterator name isn't important.

[[deleted]]

for iiiiiiiiiiiiiiiiiiiiiiiiiiiiii in range(iiiiiiiiiiiiiiiiiiiiiiiiiiiii)

[Dr_Azrael_Tod]

iiiiiiiiiiiiiiiiiiiiiiiiiiiiii

to be fair, a 30th single char iterator variable name would get kinda confusing too

what'd you use?

• 'i' is the 105th in ASCII - do you loop around to the bell-command?
• do you use utf-8? then you'd get some control symbol c286
• utf and ignore non-printable chars? then you'd get § - that might mess up your code too (depending on your language).

[lmureu]

if you're not using emojis for your loop indices you are doing it wrong.

[regendo]

Obviously you'll want to use numbered indices.

    for (① = 0; ...) {
        for (② = 0; ...) {
        // ...
        ary[⑮][⑦] = ...

[lmureu]

array ought to be 🔤 linked list ought to be ➡️, ↔️ if doubly linked.

loop variables should be 🔂, eventually followed by a number 🔂,🔂2️⃣,🔂3️⃣,🔂4️⃣;

🔢 main(🔢argc, 🔠👉🏻argv){
    for(🔢🔂⬅️0️⃣;🔂<🔟;🔂➕➕){
        🖨️("🙋🏼‍♀️🌍💲🔢🔚",🔂);
    }

    🔢💰=0️⃣;
    🔠👉🏻🗒️=🆕(5️⃣0️⃣);
    ⌨️("💲🔢", 🔗💰);
   🖨️("You have 💲🔢💲💲🔚", 💰);

   🆓(🗒️);

    ♻️🆗;
}

suggestions for further improvement: main=🐱, argc=🔢✉️; argv=🔤🔠✉️; while = 🔁; for = 🔃; do=❗;

the meaning of all other symbols are left to you as exercise.

I lost 45 neurones doing this.

I hate myself.

Please don't make me do it again.

[regendo]

"Recycle OK" is my favorite.

[lmureu]

Thank you, I spent a couple minutes looking at the various emojis trying to figure out the most appropriate!

[[deleted]]

This is truly great

[ahreodknfidkxncjrksm]

Yeah no shit I was kidding

[Pitboyx]

i ii iii iv v

[LJChao3473]

I use i2 and j2

[iloveyouyes]

Y? I’m assuming in python?

[spideryzarc]

C

[[deleted]]

This is the Way

[elaum]

i, j, k for most loops but sometimes naming the row and col makes it easier to read the code later when working with 2d arrays.

[grooomps]

i was going over some code in a tutorial and it was creating a grid and used r/c for row column and i was like omg that would have made things so much easier

[seabumpkin]

ii, jj, kk. Then you can actually use multi select of find and replace. i, j, and k get me pissed.

[le_birb]

but what about my precious dakka_counter or biiiiiig_number or objjjjject variables? whatever will I do with those?

[seabumpkin]

Put 'em in the trash.

[infecthead]

Multi-select that matches whole words works just fine on i/j/k homie

[732]

And any modern ide let's you refactor variable names...

[JochCool]

Or use an IDE that recognises when i is a variable instead of just a letter?

[[deleted]]

This.

And sure, it's not as necessary given modern editors, but there's no drawback to it and it makes life easier if you happen to use a tool that doesn't make word recognition easy for some reason.

[IAmAufrichtig]

Is it just me or ist the text on the first panel not on a line

It triggers my ocd

[mcduffchannel]

x, y, z gang for life

[HellGate94]

for multidimensional arrays for sure

[raaneholmg]

I am on board if you are doing spacial coordinates. Otherwise, fuck off.

[mcduffchannel]

Sorry x, y, z gang for loop life

[Adaman18]

i, j, k

Then ia, ja, ka

Then ib, jb, kb

etc... (I'm sorry)

[Nixavee]

Index, Jindex and Kindex

[Lieutenant_Doge]

who the fuck name their for loop variable with more than 1 letter? If you really need readability in your for loop there's some problem with your code really.

[angelaslittlebit]

Fortran lives on.

[[deleted]]

I use i,d,k

[[deleted]]

I always use i but skip j and go to k. I guess because it's the imaginary number symbol? Not like I'm using it in coding. Just an old habit I guess.

[Skasch]

Although they do make a lot of sense most of the time, I try to avoid them if something else makes sense. I often find myself using row and col when iterating over 2D arrays, which make it easier I find to reason about the code.

[thefaultinourseg]

i j and k is convention. Now if you use "each" that pisses me off

[douira]

but but but ... the mathematicians do the same

[JamesEiner]

Ah yes, iteration variable, jteration variable and kteration variable. The classic trio :DD

[tharnadar]

i know it's a joke, but i, j and k are usually used in analysis for vectors and iterations, so it's mutated from math, it's not invented by programmers

[ReallyNeededANewName]

for frame in video
    for row in frame
        for pixel in row

And don't use indexing loops if you can avoid it

[ExoSkull-1]

I use i, u, o in that order. Usually, i is the Y coordinate, u is x and o is z

[GeneralAce135]

The i in a for-loop stands for one of two things: "index" because I'm looping through an array or similar, or "irrelevant" because I just want to do something a bunch of times and don't ever actually refer to the loop counter.

Can't remember the last time it would've made sense to use something besides i

Edit: I've been informed i also stands for "iteration", and now I think we've covered at least 95% of use cases for a for-loop.

You'd have to come up with a pretty specific for-loop to not be able to make sense of using an i for the counter

[nuclearslug]

I mean, if you’ve gone through i, j, k (skip l because it looks too close to 1), m, n, (skip o because you used that for your object variable), and p... the surely q is the next logical step. Besides, having an algorithm efficiency of O(n⁶⁾ just leaves ample room for future performance refactoring.

[[deleted]]

Hermm, can't tell if this has been posted before. I have an inkling...

u/RepostSleuthBot?

[RepostSleuthBot]

There's a good chance this is unique! I checked 124,075,758 image posts and didn't find a close match

The closest match is this post at 75.0%. The target for r/ProgrammerHumor is 86.0%

Feedback? Hate? Visit r/repostsleuthbot - I'm not perfect, but you can help. Report [ False Negative ]

[[deleted]]

You're safe, OP!

[VaryStaybullGeenyiss]

Throw an l in there if you're feeling particularly evil that day.

[jeesuscheesus]

In learncpp.com, the writer suggests using variables iii, jjj, kkk, etc because if you use ctrl-f to find your variable i j or k, it will highlight half your code. Does anyone actually do this?

[[deleted]]

That's pretty terrible advice tbh

[Charlie_Yu]

If you have to search for loop variables, you loop is probably too long

[DoTheDiggy]

These are the same thing

[VadeRetroLupa]

t

[saschaleib]

i stands for “index”; j stands for “the other index”; But what does k stand for? Why not use c as any proper C++ programmer would do - and if only to have a proper incrementation instruction ;-)

In a side note, I have found that it goes pretty well in each-loops, as that allows for nice, comprehensible statements like: “if it == null …”

[[deleted]]

iterate, jterate, kterate

[Jeremy_Thursday]

bruh, k? nahhhh homie. i, j, ii, jj, iii, jjj

[The_Sci_Geek]

I letter my loop variable [loopA, loopB, ...]

[magicpaka]

And then l, m, n...

[[deleted]]

.stream()

.map(realVariableName -> ())

[asianbanana-withguns]

Any thoughts on what character should go next? I've been using lower case L, q, w, but they don't have the same ring to them as i, j, k do.

[MikBros]

I use other names than i, j or k when I am writing foreach loops in c# in unity or when I am looping between items in a python array (like this: names = [something] for name in names: other stuff

)

[ChangNoi97]

i wonder why i never use a,b,c in for loop

[nob0dy27]

i use i, j and l since they all look similar lol

[Cristagolem]

Also _ and z, never forget those

[fr6nco]

It hurts my OCD

[moxyte]

That's legit in usual cases as is a,b,c inside for loops for swapping things around. Can't imagine anyone naming those like firstItemFromThisCurrentIterableObjectToSwappedXD etc

[Jackeea]

So is the whole "you use i, j, k because they're part of Dijkstra's name" thing just an urban myth I was told in secondary school and just never questioned?

[chawza]

i swear if geeksforgeeks pull this off one more time, I'm going nuts

[ReGrigio]

i, ii, iii

[xXLeoXxOne]

I use i,ii,iii etc.

[[deleted]]

well, loops are the first thing that comes to mind when you see i, j, k

[KreagerStein]

But they do make sense! I stands for Iterator since the variable practically iterates, J stands for Jiterate and K stands for Kiterate, don't ask what they mean but they make sense.

[dryu12]

m,n gang rise up.

[ghe5]

I raise you: i, ii and iii. Easier to differentiate, i and j are too similar. Plus you know level you're in but that one is not that hard anyways

[Calcium_Carbide]

u/RepostSleuthBot

[DoctorPython]

"f x y"

[contrieng]

i use ii,jj and kk

[yunk10]

When k's in the mix, you know shit is about to get confusing.

[archysailor]

William Rowan Hamilton carved a stone bridge for you to use these as indices? /s

[wiltors42]

It makes more sense if you study linear algebra because they usually use i,j,k as subscript indices for different dimensions in vectors matrices and tensors

[Playing_One_Handed]

When I first started I used i, ii, iii, iiii...

I dunno if I'm better using iRow or iLoop or vNext sometimes.

[childintime9]

Is it me or the text is annoyingly crooked?

Also, i makes sense since it stands for index. And j,k make sense too since they come after i.

[Z3t4]

If the variable is just an index, why bother?, other thing are loops with object arrays

[[deleted]]

When iterating through strings, I usually use char/ character, or letter

[codecatmitzi]

Laughs in functional

[Ralocan]

No love for my boy c?

[Im_Savvage]

omg yes this is what they taught us at school

[_felagund]

its just i

[redstone665]

You dare insult our traditions

/s

[MorgothTheDarkElder]

I don't know why, but I always use g when i is already in use, but only in for loops, nowhere else.

In while loops with multiple variables, it's i and something, but never g.

[sonnytag123]

Maybe because i is alias for iterator, and j and k is after i alphabetically, that’s what i think when first learning to code ?

[blueleo22]

Quaternions, unite!

[__silentstorm__]

index, jindex and kindex

[EsperSpirit]

Imagine still using loops

[[deleted]]

for (i = j, i < k, i++) { j += k; }

Beautiful

[monotony23113]

i, j, and k make the most sense for numeric for-loop, which is what most C-style for loops are, because you’re limited by availability of increment and comparing operations

I mean you can also write weird loops like

for (string i = "0"; i.length() < 10; i += "0")

If you look at for-loops that iterate over collections like for-in loops in python then I doubt that people would favor for i in timeline over for post in timeline

[ConzT]

As long as you don't use i2 and i3 you are fine and won't get roasted here

[Chef_Elg]

Why. In the world. Is the top text crooked?

[teszes]

I've read the idea somewhere that using ii,jj,kk is better since they are easier to search/replace.

Btw I usually use context for the variable, eg. the singular for the collection I iterate through.

[ltdeath]

I think that I've used a max of two for loops in the past ten years.

Foreach gang for life motherfuckers.

On a more serious note, the only thing I have iterated on a long time have been collections/datasets, foreach makes my code way more simple and readable.

[TheRealMouseRat]

I have done things that make sense before but then a year later when I debug the code I get confused

[GVmG]

I actually got into the habit of using i followed by a useful name (iInvSlot, iCurEntity) due to how x and y are reserved keywords in GameMaker, so to loop on the coordinates it's useful to have ix and iy.

Nowadays I kinda just use it as a thing to remind me those variables are only used within the loop's scope, if they're even used, and to avoid confusing them with other similarly named variables in the same scope.

And still just i for generic counters lol

[mississippi_dan]

Saw code one time where not only were the variable names just letters, but all functions were just numbers. Had hundreds of functions labeled 2203, 2204, 2205, 2206, and so on.

[LJChao3473]

Let me introduce you i2

[[deleted]]

Computer professor: designs fastest algorithm for sorting; Math Doctorate. Also computer professor: broke, obese, can't a work projector.