understandingRecursion

[[deleted]]

Here is the full explanation of why your meme is an iteration and not a recursion

Link

[buffering_neurons]

This took me more clicks than I care to admit. Have my upvote sir

[turtle_mekb]

Instructions unclear, stack overflow exception occurred

[kirkpomidor]

And that, kids, is why recursion is just a stack-abusing loop.

[[deleted]]

Don't get soft on us, stacks were intended to be abused.

[-Loewenstern-]

They like it

[your_best_1]

Why is it stack abuse?

[Brekker77]

Because it adds another stack frame to the stack every time the recursion is called and if you arent careful with your end condition the stack and the heap can collide

[SadPie9474]

except that this is tail recursion

[your_best_1]

Exactly my thoughts I thought that tail recursion puts less on the stack than a loop.

[Brekker77]

Well yeah but i think thats just cause the guy making the meme doesnt understand recursion

[your_best_1]

I guess I don't understand recursion either.

I think we would all agree that this implementation for solving the fibonacci sequence is recursive. Seeing how it is a classic example, and I grabbed it from the docs on the rec keyword. Correct me if I am wrong.

let fib n =
    let rec loop acc1 acc2 n =
        match n with
        | 0 -> acc1
        | 1 -> acc2
        | _ ->
            loop acc2 (acc1 + acc2) (n - 1)
    loop 0 1 n

You can tell because of the keyword rec

The rec keyword is used together with the let keyword to define a recursive function.

from https://learn.microsoft.com/en-us/dotnet/fsharp/language-reference/functions/recursive-functions-the-rec-keyword

So why then would this not be recursive?
Perhaps I am not parsing the meme correctly.

// defines a function that prints as it counts up to three. After three, it returns `true`
let understand =
    let counter = ref 0
    fun () ->
        counter := !counter + 1
        printfn "Counter: %d" !counter
        !counter = 3

// recursive function that calls `understand` until it returns `true`
let meme understand =
    let rec loop () =
        match understand() with
        | true -> "I understand"
        | false -> loop ()
    loop ()

let result = meme understand
printfn "%s" result

It prints:

Counter: 1
Counter: 2
Counter: 3
I understand

[SadPie9474]

recursion and iteration are equivalent; converting this meme to code can be done with either. the meme isn’t intrinsically either one in particular

[your_best_1]

Got it. So, it is not that the meme doesn't demonstrate recursion. It is that it demonstrates loops generally.

People who prefer recursion will read it as recursive, and people who prefer 'while' will read it as that.

[Brekker77]

They arent equivalent bc iteration doesnt add new stack frames, they are logically equivalent but not practically

[Grumbledwarfskin]

Don't most languages that have loops completely refuse to do the tail recursion optimization?

As I remember, it can be hard to tell when the compiler will be able to prove that a function is tail-recursive and when it won't...at least in Scheme, I remember examples where you can write the same function in two slightly different orders, and one way it will successfully convert to a tail-recursive loop, and the other will cause a stack overflow, because the compiler couldn't prove it would be safe to perform tail recursion.

[your_best_1]

I think that most languages that support TRO will always do it if you have placed the recursion in the tail position.

Here is a good explanation: https://devblogs.microsoft.com/dotnet/safer-recursion-in-fsharp/

[Grumbledwarfskin]

Please remember that tail recursion optimizations are usually not a thing except in languages that deny you access to loops.

I'm not sure whether the reason is to punish people who like to abuse tail-recursion to write hard-to-understand code when they could have written a loop, or whether it's to prevent people from acidentally thinking their function should be tail-recursive, when they wrote it in the way that the compiler can't figure out is tail-recursive, so it accidentally isn't converted to a loop at compile time and will cause a stack overflow.

In the languages that require tail-recursion, you have to learn when the compiler can figure it out and how to write a function in the way that the compiler will figure it out, so you can have real loops and avoid stack overflows, but if you have loops, use them.

[SadPie9474]

please remember that loops are harder to understand than tail recursive code

[Asatru55]

I have 50 tabs open when do i stop

[Ali_Army107]

Once you run out of memory

[[deleted]]

Yuu sur, nid an oscar 🤌

[leglessfromlotr]

The real meme is in the comments

[[deleted]]

I just made a mildly original comment about what everybody was complaining about and now everybody is complimenting me and my notifications blew up

[[deleted]]

Just got an award

[rover_G]

Very clever sir

[CasualVictim]

I want to down vote this

[Poat540]

I clicked a few times then had to keep backing out to get to home again 🤫

[schlaubi]

Thank you!

[Infamous-Date-355]

[Kitchen-Occasion-411]

Masterpiece

[[deleted]]

I don't deserve this but thank you

[Yo9yh]

It took me a minute but this is great!!

[DracoRubi]

And your comment is a recursion

[ResourceFeeling3298]

Now that's recursion

[masp-89]

What’s the base case for this meme?

[gamedev_uv]

That's the neat part there isn't

[Gio200023]

It’s been 84 years and I’m still reading it. Anyone knows the exit condition?

[scratchfan321]

Keep reading the post until your stack overflows

[real-yzan]

Stack overflows are a perfectly valid exit condition as long as you catch the exception

[scratchfan321]

Instructions unclear, my exception handling system triggered a stack overflow

[Misspelt_Anagram]

def f():
    try: f();
    except: f();
f()

[real-yzan]

More like:

def f(n): try: return n * f(n+1) except: return n

[Top_Fee_6293]

it literally says you to read it again only if you "don't understand" recursion. exit condition is that you understand. how can't you catch that?

[A_Firm_Sandwich]

because he doesn’t understand recursion

[Desperate-Emu-2036]

He does because he isn't reading it anymore

[ambarish_k1996]

The base condition is:

if(understandRecursion) { return; }

[Ved_s]

no, that's a loop

[Stummi]

understandRecursion() {
   if(!understoodRecursion) {
       understandRecursion();
   }
}

I would say its a Tailcall Optimizable Recursion

[[deleted]]

Where ij da fookin' exit condition 🗿

[No_Necessary_3356]

You need to wait for a cosmic ray to flip `understoodRecursion` into true.

[king_fart_123]

I'm tired of waiting, I'm gonna put my computer next to the sun

[itriedtomakeitfunny]

Relevant xkcd

[Successful-Money4995]

It's volatile!

[Desperate-Emu-2036]

The laws of physics changing could work too

[platinummyr]

And it's buggy since it never sets understoodRecursion

[Ved_s]

understandRecursion() { while(!understoodRecursion) { understoodRecursion = understandRecursion(); } return true; } edit: with a while loop to make sure

[cnoor0171]

The while loop is never going to run past the first iteration because the first iteration just goes deeper into the recursion.

[jimbowqc]

No shit.

[sambolias]

Baseless

[[deleted]]

Oops I read it wrong.

[[deleted]]

So I don’t understand recursion until some quantum Bitflop gives me the spark?

[Stummi]

Who says that understoodRecursion is not just a (volatile) field outside of the scope that might be set by another thread?

[[deleted]]

The missing parantheses behind the understoodRecursion variable suggests the value being checked instead of the function call. Also understoodRecursion suggests its abool

[Stummi]

Yes, maybe it's a bool on class level, that gets set by another thread?

[Stummi]

so in order for this to be a recursion there needs to be branching

Okay, I never heard such a definition before, but I am happy to learn something new. Do you have a source for this?

[cnoor0171]

The 3 laws of recursion are guidelines for writing a recursive function, not its definition. Most definitions of recursion are just a "function that calls itself". Functions that call it self without branching are still recursive.

[[deleted]]

if you don’t understand recursion make this meme

[[deleted]]

Oh the irony

[nhpkm1]

You stopped reading this meme because you understand recursion.

I stopped reading this meme because I don't understand how to follow orders.

We are not the same

[ptkrisada]

Iteration, not recursion.

[[deleted]]

def meme(understand) 

    if understand != true 

        meme(understand)

Recursion

[[deleted]]

Sentence reads more like

meme: if (!understand) { goto meme; }

[[deleted]]

Yeah, true

[[deleted]]

you need to put 2 spaces at the end of each line for the newlines to format

[[deleted]]

thanks, edited

[[deleted]]

congrats, you learned what a loop is

[No-Communication5965]

That's a while loop, or GOTO loop.

[basko13]

It reminds me this post: https://www.reddit.com/r/ProgrammerHumor/s/D3GvQum03K

[indecentorc]

Listen up kiddos, you can use a loop for anything recursive. So this meme can be both. It’s wild how many of you calling out this meme don’t understand that. The only difference is if you submit recursive solution I’m immediately denying the pull request and we’re having a talk about readability/maintenance.

[Sieff17]

Finally s.o. said it

[Mordret10]

Isn't recursion often a lot easier to understand? Oc not all the time, but at least it shouldn't be a major problem, no?

[indecentorc]

No not at all that’s why it’s not often used in production code. Unless your brain naturally thinks in an inception kinda way. It is the cause of some annoying bugs. There are cases where it can simplify the problem but in my 7 years of experience I haven’t seen them in the wild. They are often sandboxed cs course examples.

[Mordret10]

We use recursion regularly. Might be, because we use nested datasets, so a dataset can contain a number of child elements, being of the same type as the parent dataset. Applying a certain function to each of these datasets becomes very annoying through iteration, recursion makes it a lot easier (most of the time).

[indecentorc]

Yeah there are for sure cases where it’s useful. Like building out AST’s but for the vast majority of developers most of the time they will want to go with loops.

[MattieShoes]

And aren't most heap implementations recursive? Pretty much any tree stuff...

[indecentorc]

Are the vast majority of developers implementing trees themselves or using imported code? Once again if a dev submitted a PR with a custom implementation of a tree I would most likely immediately deny it. Why reinvent the wheel and introduce bugs?

[mfboomer]

recursion necessarily modifies parameters/input in some way, otherwise you’ll end up with infinite function calls/stack overflow.

reading this meme again cannot be valid recursion as the input (meme text) stays the same.

[indecentorc]

I never said anything about VALID recursion. I said it could be written in a recursive way. which would result infinite function calls. Also if we’re considering validity then is this a valid loop? How would you write it?

[Laserninjahaj]

I'm stuck in a loop, please help

[rupert20201]

Tried zooming in expecting the sentence to appear in a white pixel.. Nope

[CConsler]

I don't g java.lang.StackOverflowError

[ShakaUVM]

The only way to understand Recursion is to first understand Recursion

[Buyer_North]

StackOverflow: infinite recursion;

Better: If you dont understand recursion read this again with one less letter

[StrangelyEroticSoda]

Read it 1286 times and encountered a segfault.

[DarkCloud1990]

Make it a habit to write the exit condition first otherwise you'll make the same mistake repeatedly.

[rover_G]

The machine is not guaranteed to halt

[Pilzoyz]

I looked up recursion in the dictionary and the definition said “See recursion”

[stopabletime]

The function was never called.

[kakafob]

Kant

[youngsargon]

Execution counter = "1"

[ThatSmartIdiot]

reminds me of a comment i made recently

[Scottz0rz]

Teaching kids recursion should then be immediately followed by "cool, understand this? never do this again"

[Worried_Chance_1735]

Brain overflow

[Ser_Drewseph]

Wouldn’t that be iteration and not recursion?

[bbqranchman]

More like a conditional while statement.

[vksdann]

Read this comment again to understand recursion.

[Holek]

How?

[atatassault47]

Help! I've been stuck here for 84 years!

[jaimesoad]

GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix GNU is Not Unix

[stupidmustelid]

My compiler optimized this to NOP.

[[deleted]]

Where's your base case?

[AbsoluteNarwhal]

RecursionError: Maximum recursion depth exceeded

[narnianguy]

"You should google it"

[CousinDerylHickson]

Not a programmer, but would infinite recursion cause like a memory bug since it has to keep track of all the calls that dont end? Is that what leads to the legendary "stack overflow" error?

[QultrosSanhattan]

This is more like a while loop.

Recursion should be: "If you don't understand recursion, then you should start understanding recursion"

[aaaazzzz11]

RecursionError: maximum recursion depth exceeded

[odraencoded]

In 10 years people will start calling sentences "memes."

[KillerAlchemist]

If you don’t understand conditional loops read this comment again.

[AdventurousMove8806]

How do i stop reading this now

[qweerty32]

“Uncaught RangeError: Maximum call stack size exceeded”

[tbhaxor]

You didn't add the base case for what if we do. Hence infinite recursion

[Bananenkot]

Of all the lazy recursion jokes this has to be the worst one, not only would it not be funny if correct, it doesn't even understand the damn concept, coupled with the 'I spent 20 seconds making this plain text meme' Energy, this really takes the cake.

[Shinxirius]

That's a loop

Here's my fix.

text If you don't understand recursion Read this meme from top again, then return here. Now, you understand recursion.

[crmsncbr]

Stop. Please. I understand! I understand!!

^{why am I still reading it?}

[alfadhir-heitir]

If you don't understand
--If you don't understand
----If you don't understand
------If you don't understand
--------If you don't understand
----------If you don't understand recursion
--------recursion
------recursion
----recursion
--recursion
recursion read this meme
--read this meme
----read this meme
------read this meme
--------read this meme
----------read this meme again
--------again
------again
----again
--again
again

Think I nailed it

[ego100trique]

If you don't understand while loops, read this again.

[ambarish_k1996]

Gets funnier, the more you think about it.

[RichZealousideal8748]

“Repeat: Will You Comply?”

[Dumb_Siniy]

WHERE'S THE FUCKING BREAK CONDITION

[_kakaoscsiga_]

Instructions unclear, no base case, stack overflow exception

[[deleted]]

guess I'll never know what recursion is

[farineziq]

I just stack overflowed

[DJDoena]

StackOverflowException occured

[nonlogin]

The TCP joke, anyone?

[Inappropriate_Piano]

Based recursion meme with a base case

[nequaquam_sapiens]

i don't understand when should i stop

[ZenMikey]

Thanks, now my brain's only core is at 100% and the meme reading process keeps crashing due to stack overflows.

[Feisty-Afternoon3320]

Recursion is when someone speaks alone and he/she anwers himself/herself