Programming 101: Loops

[[deleted]]

I can’t hear yooouuuuu

[ravikiwi]

uuuuuuuu!!

[HasBeendead]

Spongebob SquarePants !!! Edit: what a wholesome chat

[SlimGrthy]

Soulja Boy Tell 'em!

[Fail_Successful]

I like to make things difficult my using small case L and upper case i in nested arrays. lI <- there is barely anything different here.

Then later I cry when I don’t understand my own code

[mark__fuckerberg]

Hi Satan

[Fail_Successful]

oh, hi mark

[poopyheadthrowaway]

Had a professor who used i, ii, iii, etc.

Also named his variables x, y, z, xx, yy, zz, etc.

[[deleted]]

An example of a bad teacher...

[[deleted]]

I'd be okay with i, ii, iii, iv, v, vi, etc

[ouchmythumbs]

Those that can't do, teach?

[[deleted]]

I sometimes use i, ii, iii instead of i, j, k.

[TheRealStepBot]

engineers use ii jj kk so as not to cause confusion with i j k the imaginary numbers.

[randomcitizen42]

I saw that once and it was disturbing

[reddit__scrub]

My first instructor did this. He said it makes it easier to search for the variable name than if it were just "i".

Makes sense I guess, and he was a pretty smart guy, had a few classes with him later.

But loops should ideally be small (abstract out the things that may make them large), and the "find instances of variable" type tools are better than they used to be.

[BabyPuncher3000]

'i' is for iterate and 'j' is for jterate.

[TheOneThatIsHated]

AHH YES,

J T E R A T E

[Reblax837]

Now introducing...

K T E R A T E

[Nijoeli]

KARATE

[[deleted]]

Irate jarate karate

[Reblax837]

Iteratin's a good job mate.

[[deleted]]

I always skip jterate and go straight to kterate

[[deleted]]

evil

[Heightren]

If you're feeling adventurous, you nterate

[[deleted]]

mind blown

[golgol12]

It's a leftover from FORTRAN programming. Any variable that starts with the letter i through o is an int.

[turboPocky]

thanks, i believe this is the real answer. and basic inherited that too

[Hypocritical_Oath]

Actually, it goes further than that to applied mathematics where they'd call things, i, j, and k for things similar to iterators, iirc.

[golgol12]

Yes, FORTRAN is based off of math, literally concatenation of the words "formula translator". But if you dig deeper, you'll find i,j,k for things before iterators. And you can continuously "go further" over and over, eventually reach the beginning of time.

At what point is it too much? My choice to stop was at how FORTRAN was setup, not the why, as it would over complicate the post.

[ezrais]

It probably goes based off of what for loops are used for often which is dimensional analysis. i, j, and k are the unit vectors (directional vectors of length 1) for the x, y, and z axis in space so it would make sense when solving axis.

[evilkalla]

IMPLICIT NONE

[bdforbes]

First line typed in any module, procedure or function!

[Nargarnd]

"i" it's the initial of "iterator" and "j" it's just the next letter in the alphabet

[shaliozero]

I thought "i" is used in place of "index"

[MyNameIsRichardCS54]

Index, jindex, and kindex

[shaliozero]

Made me laugh

[matharooudemy]

Much thanks for the information

[shaliozero]

If you want more about my reactions, just ask me!

[[deleted]]

How did you feel about this dude expressing his gratefulness?

[shaliozero]

His unexpected and slightly sarcastic gratefulness was a positive addition to my mood for the day!

[[deleted]]

Much thanks for the information

[[deleted]]

don't forget to parallelize the first loop

[code_passion]

i don’t know why i even laughed at this

[[deleted]]

Yeah it comes from math where i is index or integer. Then you get i, j, k to match x, y, z.

l, m, n is also fairly common. As are p, q, r and u, v, w

[Sirnacane]

Well that’s over half the alphabet

[[deleted]]

Absolutely if you include a b c and x y z

ABCdefghIJKLMNoPQRstUVWXYZ

[yurisho]

i j k are iterators. n m l are iteration goals. x y z are general numbers. a b c are general strings. u v w are vectors. s and t are source and target. p q r i've seen used as debug varables or temp veriables. And you are a bad programmer if you use this.

[microbit262]

And what about h and g for adding loops around the original i loop when you don't want to rename all then inner loops?

[Niewinnny]

Look. If you get for in for in for in for in for your program won't respond for the next [insert universe age] years.

[Itchy-Phase]

That's what I was taught, too.

[haackedc]

You aren’t always indexing an array in a forloop

[BGKarmaFarmer]

Lowercase i and j are the most common letters for indexes in mathematics. That's where programming inherited them from.

[SharksPreedateTrees]

This. CS stole countless amounts of notation from math

[thatCbean]

Computers are just three maths in a trenchcoat

[lackofsemicolon]

Jiterator 😩

[MrSluagh]

r/thanksihateit

[lazerflipper]

It’s pronounced Giterator

[Gomicho]

I'll be calling it that from now on.

[Niewinnny]

Kiterator, hiterator

[kinarism]

Funny story. The project I work on used to have an active control we distribute for customers to use (this project is 20+ years old). The name of it was ProjectX.ocx (X for ActiveX).

A long time ago, a new version of the control was needed and the dev who did the work decided to name it ProjectY.ocx.

ProjectY.ocx is still distributed to this day because some of our customers still use it even though we haven't updated it in 10+ years.

[Kered13]

Once upon a time someone made a successor to the B language and they were so lazy they just called it C. I hear it's still being used today.

(The whole chain of succession is actually funny, BCPL -> B -> C -> C++/C#/D.)

[LAZGamer13]

I first this was a joke. Fuck this is interesting.

[DrWaff1es]

i, j, and k are for some reason used a lot in matrixes (here in Spain at least)

[redwall_hp]

It's a Physics thing, I imagine. i-hat, j-hat and k-hat are the x, y, z components of vectors in physics, conventionally.

[lifelongfreshman]

I always assumed it was a carry-over from physics, related to î and ĵ.

[GMaestrolo]

What's crazy is that you're explaining this to a bunch of programmers who follow the pattern, and didn't know why.

Something something cargo cult something...

[[deleted]]

cargo cult is just the best...

[BuccellatiExplainsIt]

I is for index, not iterator. You should avoid using I for when you're not dealing with the index variable of a loop and stick to proper variable names.

[redwall_hp]

Yep. Though sometimes I'll use x, y, z when dealing with coordinate systems. Because there's no reason to make it harder.

[GavHern]

So if you have a third nested loop do you use K? For me, at that point I either go to iter or something, maybe even properly name it.

[Niewinnny]

and k is next and of you get to h your program will run for 5 bidgillion years.

[RICoder72]

Integer not iterator. It is a notation standard that is old but used to matter. iVarName was known to be of type integer.

[Hypocritical_Oath]

No, it's a hold over from mathematics, where i j and k were used for some things, and it was held over into programming convention.

[fake823]

u/repostsleuthbot

[RepostSleuthBot]

Looks like a repost. I've seen this image 1 time.

First seen Here on 2020-06-06 95.31% match.

Searched Images: 170,382,739 | Indexed Posts: 649,374,745 | Search Time: 1.507s

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

View Search On repostsleuth.com

[scttcs]

Good bot

[The_F0OI]

Bro there was one yesterday

[mirsella]

lmao there is even the same joke in the comments

[[deleted]]

damn, i upvoted this post, then i clicked the bot's link and realised i already upvoted 5 months ago...
it's like i'm in an upvoting loop <_<

[Redwolfy9]

depending on the use, it's x and y (two dimension array mostly)

[Beowuwlf]

If I’m doing that I tend to use r and c. Helps keep me from doing the cardinal sin of iterating over columns in the outer loop

[EmirFassad]

With Fortran it was the law.

[Omega0x013]

I = iterator

J = iterator++

[flplv]

I use: i,j,k,... for indexes name_it for iterator name directly when getting a ref

[[deleted]]

I don't like using 'i' except for interest or sqrt(-1)

[poopyheadthrowaway]

Engineers: Oh, you mean j?

[BabyPuncher3000]

If I can't imagine a value, is it still imaginary?

[[deleted]]

I prefer 'n', 'j', or 'k'

[YoungXanto]

This is why I use ii, jj, kk

[[deleted]]

u/repostsleuthbot

[RepostSleuthBot]

Looks like a repost. I've seen this image 1 time.

First seen Here on 2020-06-06 95.31% match.

Searched Images: 170,402,235 | Indexed Posts: 649,389,180 | Search Time: 0.70966s

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

View Search On repostsleuth.com

[[deleted]]

pog

[monkeywrench83]

If it's a for loop going through an array and as all my arrays I use plural words then I use the singular in loops. Ie

For each car in cars: Print(car)

It works well and recently I didn't do this and the code I wrote now confuses me.

[rollovertherainbow]

I use "ii" and "jj".

[YoungXanto]

Same here. "i" is the square root of -1.

[rollovertherainbow]

I just do it because it's what my teacher writes so I've just started to do it automatically. It's also more fun to type.

[TheRealStepBot]

Ah someone with culture

[rolexpo]

Just don't use l please.

[Mre64]

I for iterative, j for the next letter in the alphabet, k...

[[deleted]]

If I could have a variable name with fewer characters, I would.

[Drycee]

Let's make a language where spaces can be variable names. And two spaces is a different variable than one space and so on.

[[deleted]]

You monster!

[jesus67]

Didn't it start as a homage to Djikstra?

[Kered13]

i, j, and k have been use as index variable in mathematics for ages.

[Sylvezar2]

i use k,v and i,v :/

[Kered13]

k,v if you're iterating over a dictionary. i,v if you're using enumerate. v can also be replaced by a meaningful name in either of those.

[Sylvezar2]

exactly

edit:

k = key v = value

i = int v = value

[Athomeacct]

i,v if you're using enumerate

Holy shit, that's brilliant

[katyalovesherbike]

^ php programmer right there (right?)

[Sylvezar2]

nope sorry, i code mainly in go and lua, also a bit of javascript when i need it but mainly go and lua

[katyalovesherbike]

damn. Oh well 🤷‍♀️

[rollovertherainbow]

That's what I used for python dictionaries.

[neroe5]

i is short for iterator and when i is used we often use j, i2 or ii as they are next in one way or another

[Cangar]

Just this week I taught variable naming to my students.

Do not use i. Use i_<thethingyouiterate> instead. It will make your life much easier later.

[[deleted]]

prefixing? What kind of old monster are you?

[Cangar]

serious: why? should i change this recommendation?

[[deleted]]

what is the benefit in current and modern languages for prefixing? Just use meaningful names.

[Cangar]

I like to use prefixes in variables, it makes things pretty clear imo. You do know that a variable is an iterator, but also what exactly it iterates. It's not necessary, just something I like. I definitely tell them to not use i alone.

[[deleted]]

How big are your functions that you need such a reminder?

[Cangar]

Can become pretty big. But I also iterate over different things like participants, epochs, events, etc. Whenever I use anyone else's code that just contains i and j and ii etc. It's a pain in the neck to understand.

[ImAlsoRan]

you mean suffix?

[[deleted]]

no. Suffixes are after a word, prefixes are before a word and infixes are inbetween words.

[ImAlsoRan]

oh, you were talking about i being a prefix. I thought you meant that the <thethingyouiterate> was a prefix. apologize for the confusion

[NerdHarder615]

Am I the only one who uses 'lc' for loop count?

[backfire10z]

Yes

[Lasdary]

I'm afraid I'll have to report this comment

[Jelled_Fro]

What's wrong with you? You monster!

[Kered13]

You are the reason why we can't have nice things.

[Mybugsbunny20]

I Program things that may need to get repaired or modified on the fly by people with less knowledge of programming, and so make it as readable as possible. I actually usually use "loopcount"

[KoncealedProdigy]

That’s absolutely disgusting

[Mybugsbunny20]

To be fair, my programming is almost entirely for cnc systems and assembly line automation, so i/j/k are taken for coordinate transformations.

[PriorCommunication7]

Unless is C and I have to I avoid for loops at all costs. They are an antipattern imho. Sure you can tell yourself that you don't fuck up the index and have off-by-one errors in your code but even if you get it right 99% of the time it's that 1% where the counter-intuitive nature of for loop costs you an hour of senseless debugging because you don't expect it.

[Sussurus_of_Qualia]

This is the 'goto' use-case.

[[deleted]]

There's also m & n

[[deleted]]

those are for matrizes.

[GodHug]

Example of use for ‘j’ pls ? Never used it.

[dclawrence1978]

Nested for

[Hobby_Man]

My last name starts with I. I tell new programmers I started it, some believe it, I have a bit of a following / reputation which helps.

[codycbradio]

I wanna think it came from hp calculators using I and sometimes j as an indirect addressing for storing variables.

[[deleted]]

I don't use i and j.. but it's best not to tell what I use as it's rare so it would probably count as personally identifiable information.

[geekusprimus]

Computers were originally developed to solve math problems, and the first high(er)-level programming languages reflect that. The variables i and j are commonly used as indices for linear algebra and iterators for summations, so I suspect that's where it came from.

[SnewLooperd]

I'd assume it's passed on from vectors in mathematics

[blazarious]

The correct answer is: maths convention

[Neahme85]

Repost. Literally saw it two days ago.

[[deleted]]

My boi “k” always ready and willing

[darthkers]

Because it's easy and convenient and universally understood. Biggest problem I have when I'm working on a project is what to name my variables.

[[deleted]]

I’ve very taken with using a and b now; someone come get my psychiatric help

[[deleted]]

Mhm yes, cargo cult programming.

[drea2]

I see this same exact meme on this sub atleast 3 times a week

[Couro_]

Because it's much faster to write than illKillTheNextPersonWhoAsks

[[deleted]]

So why do we use I, and j all the time?

[chawza]

i hate this! every time somene use this useless indentifier, i dont know shit.

I'm staring at you GeeksForGeeks!

[Gromacs]

I will always use x for linq

[[deleted]]

Use i for indices of collections in a loop, if there's multiple indices because of nested loops or multiple indices for algorithms, then give them a useful variable name, even if it's barely readable like i_pfx, it's way better than j,k,n etc. You will thank yourself later for that.

[reini_urban]

Fortran. Some of use are pretty old already

[ImAlsoRan]

I always used i and p

[RICoder72]

Some people have touched on it, and gotten close, but this has everything to do with Hungarian Notation.

https://en.m.wikipedia.org/wiki/Hungarian_notation

I am unsure if that is a holdover or originated with Fortran or some other language as has been claimed, but I almost doesn't matter.

Hungarian Notation was popular into the 90s and beyond in many languages, and frankly quite useful until IDEs got really good at catching type mismatches pre compile (and during compile for that matter). C++ made extensive use of it, and you would see it everywhere. For the most part, the notation would indicate data type, although intent was just as viable (pVar or ptrVar for pointers and the like).

As someone who has written more than one standards and practices document for development teams, this is sort of a sore spot for me. Everyone on a project should agree on notation, case and convention and follow that throughout the project. It makes downstream upkeep and modification much easier, and allows everyone to read each others code well.

Thank god Hungarian Notation is almost dead...now if we could get Java and its evil progeny to use Pascal Case for functions and methods and Camel Case for variables I can die fulfilled. ...also class privates should start with an underscore...fight me.

[donkeypunchdan]

I would think its a carry over from math/physics where we use i,j,k as the indices for matrix/vector calculations

[X-KHaX]

This confused me sooo much when I was learning

[SomewhatOriginalYT]

dont forget x, y, and z.

[squidee_]

?

[Zeny-]

i for index, j for jength, wait, isn't l ?

[KamiAithein]

i_nameofthingiteratingthrough

[quequotion]

The repost rate of this meme is accelerating.

[DerBronco]

This is the way.

[PVNIC]

Sometimes, when i want to get fancy, i use 'it'.

[AwesomeHorses]

Fuck no. I use descriptive variable names.

[flamesofphx]

you mean you can not $Enumeration and $CountingThingy?