The Nineteenth Byte

ln(e^x) = x

@Qwerp-Derp (x^2-1)^2 is x^4-2x^2+1, not x^4-1

Whoops

@Zgarb Oh wait whoops

@flawr Yes. The ordering gives a more refined result.

10:07 AM

I got confused with difference of two squares

@Zgarb that is really neat!!

So the end result should just be x^4-2

@Qwerp-Derp just expand them both separately first, that helps

"If f has a periodic point of least period m and m precedes n in the above ordering, then f has also a periodic point of least period n."

@Zgarb Are you working in this field??

10:10 AM

A subfield of it, yes.

What characteristic? XD

Actually no it should just be x^4

Wait you can still substitute x in if p(x) is something like (x+1)^2 right?

@flawr It's a subfield so the characteristic doesn't change. :P

@Zgarb Well we don't know about the characteristing of the greater field in the first place :)

@Zgarb Anyway that seems like a really cool topic. I've only ever heard about dynamical systems without ever having the faintest idea on what it is about

@flawr Deep down it's just having a function and iterating it.

10:14 AM

So is it considered as part of number theory?

No no no, it's closer to analysis and topology. Although I work on discrete systems, like cellular automata and such.

Hm I was always strangely attracted to things with iterated functions ever since I first heard about the banach fixed point theorem. I recently tried to solve some tasks in haskell with the idea to write them in a way such that their solutions is the fixed point of some function, and that repeated iteration of that function converges to that fixedpoint=)

For example, Sharkovskii's theorem holds for an interval I of real numbers, and a function from I to itself. The topology of the reals is really important in the proof. The theorem does not hold if I can be the circle, for example.

I think I've got another answer to the "Will the code terminate" question

@Zgarb How about I = (-inf,inf)? or I = [0, inf)?

The example about the circle makes totally sense!

10:20 AM

@flawr It'll work on those too, I believe.

I think one guy in our department works on dynamical systems on rational maps, if I understood that correctly. But he's a number theory guy, as far as I know=)

Rational maps do sound like number theory. Dynamical systems have lots of applications there too.

Anyway, I sandboxed a challenge about the theorem yesterday. Does it look clear to you?

So many Darth Vader hats in the chatroom.. (I'm looking at you @flawr with your oversized hat)

@Zgarb I think it is quite clear.

I think sorting does apply here

Does anyone want to play a round of Fourtune?

10:27 AM

Well, the programs don't really have to sort anything, just indicate the order of things.

If you want to play Fourtune, ping me at the Fourtune room

Jarko Dubbeldam

I got a secret hat :o

But on the other hand, that sounds like sorting.

@Zgarb Still, the tag description still fits I think. Just one questoin: do the listed criteria p=0 or q=0? (and the case m=1 or n=1?)

Jarko Dubbeldam

Not sure how I got it though.

10:28 AM

@JarkoDubbeldam that is the point of a secret hat

@flawr Ooh, right, 1 should be 0 for p and q.

Jarko Dubbeldam

figured, but still curious

No wait.

There.

@Zgarb let me test it=9

Destructible Watermelon

hi I'm back

10:36 AM

I did it!

My answer is the most upvoted answer and the longest answer!

@betseg For what question

Third longest actually, but you get the point. codegolf.stackexchange.com/a/103831/56721

@Zgarb Can you find the error here?

Oh damn tabs

79

Q: Does the code terminate?

This is a code golf challenge I thought of with a mathematical bent. The challenge is to write the shortest code possible such that it is an open question whether or not the code terminates. An example of what I mean could be the following piece of python code, adapted from an anwser to this cs s...

Yay I uploaded another solution to this challenge

@flawr Use TIO.

10:47 AM

(Which is probably dead)

ooh

didn't now TIO has haskell!!!

TIO has everything these days.

Do I have to write a main?

TIO has Clojure, which is nice

Yes, but you can put it in the header.

10:49 AM

The only downside to coding in Clojure is that it doesn't get votes

Lembik

at least you get clojure though...

@Zgarb Try it online!

gist.github is very strange at the moment: When I tried to paste a multiline piece of code into a gist, it first accepted it, but then instantly turned it into one line

@Zgarb What exactly is the header and the footer in TIO here for?

You can wrap your code into some boilerplate or test array, and it only counts bytes for the middle part.

Aaah I see!

PS: I just tried to run all kinds of test cases and your set of criteria seem to work

code-golf code-challenge calculator

Protip: don't use tabs with Haskell.

New Main Posts

10:54 AM

0

Q: Brick a calculator

Obviously, don't test any of the code below on real devices. If you do, it's your darn fault that your calculator is now useless. The objective is to render any model of a programmable calculator permanently inoperable with the shortest amount of code possible. Score is calculated as (# bytes i...

@Zgarb NP++ made those damn tabs, that why stuff wasn't working earlier....

You should set it to replace tabs with spaces.

It'll save you from many headaches.

Or use an editor with smart indents, like Emacs.

I kinda want to see a tinylisp answer to the tinylisp interpreter thing

@Zgarb good idea, it would probably have saved me a few hours by now=)

oooh cool, you can set it per langage!

@Zgarb Back to dynamical systems: Is there some kind of "classical" introduction that you can recommend?

@flawr I don't know as much about the general literature than I'd like. But I've heard good things about this. It may be above your level though.

11:07 AM

BTW (no context): How to gut a typical fish shaped fish.

@Zgarb Let's see, it is on lib gen.

@flawr This may be easier.

@Zgarb It seems to have a lot of pictures, I like that=)

@Zgarb Thank you for the recommendation, I'm probably not gonna read much of these books, but just to get a first taste=)

@flawr One more, then I'll stop. Check the "topological and symbolic dynamics" links. This one I've actually read through.

11:23 AM

@Zgarb thank you very much=)

I just skimmed through the first few pages of the first two books, both look great!

BUMP

Comments anyone? I want to make this, but I've received very little feedback (one comment in chat: "Could be interesting").

11:38 AM

@StewieGriffin I think that's a great code-challenge idea. Scoring will have a random element, but hopefully the solutions will be fast enough that you can run thousands of trials.

in Colors, a Trading Card Game, 3 mins ago, by zyabin101

I want to make a new set. :3

20 runs seems small when the game is this complex.

@Zgarb Yeah, I've thought about the randomness of the scoring, but the only way I could make it non-random was to force everyone to use the same stream of numbers, but I don't think that's a good idea. Running many trials should reduce the effect of the randomness.

@Zgarb I agree... I'll increase that number.

You might also want to give a time bound to prevent exhaustive simulation (I doubt anyone would bother with that, but you never know).

@Zgarb Good point, but a bit tricky to formulate and decide where to set the limit.

It can't be too long, if the code must run 100/500/1000 times.

11:50 AM

Yeah, and you can't really know the right number of runs beforehand since there can be lots of variance.

@StewieGriffin I remember Martin having a "soft time bound" in one challenge. You could have something similar, like "Your program should be able to run 100 iterations in about one minute on my computer [specs here]. This is a soft bound: if it takes 1.5 minutes on my end, I'll give you the benefit of the doubt, but 3 minutes is too much."

Replace 100 iterations/min with something you're comfortable testing.

@Zgarb That's a good idea :)

12:07 PM

The number of iterations for scoring could be flexible too: "Your final score is the average of your program's scores over 100/500/1000/whatever runs. I reserve the right to increase the number of runs if needed."

Conor O'Brien

@Mego oops. I thought the question looked fine

@Zgarb I wonder if I would have to ask someone to volunteer to do the testing... I only have Python, MATLAB and Octave installed on an old windows machine. If someone throws Haskell or C# at me, or if something requires Linux I'd be lost...

Oh, and it would be good to include the Yahzee score card in the challenge text, and to clarify the rules a bit. IIRC, you have 13 score boxes, and you roll the dice 13 times. Every time you must either score an applicable box or discard the roll.

@StewieGriffin Okay, that might be a problem...

@Zgarb Yes, I'll add the score card, scoring rules, rolling rules etc., so you wouldn't need any prior knowledge. I haven't done it yet though :)

@Dennis Can TIO be reliably used to score a code-challenge like this one?

Or does its speed "fluctuate"?

(There will probably be a time bound in the challenge)

12:16 PM

^^ But not a very strict one. Something similar to Martin's rule on some challenge, here

Does anyone play HRM here?

-- HUMAN RESOURCE MACHINE PROGRAM --

a:
    INBOX
    COPYTO   0
    OUTBOX
b:
c:
    COPYFROM 0
    JUMPZ    e
    JUMPN    d
    BUMPDN   0
    OUTBOX
    JUMP     c
d:
    BUMPUP   0
    OUTBOX
    JUMP     b
e:
    JUMP     a

@Qwerp-Derp Not me.

I need halp optimising stuff

HALLO

Human Resource Machine?

12:18 PM

@zyabin101 Yup

Do I need to pay for it?

My internet is finally up, yay \o/

@zyabin101 Not if you know where to look

It's a fun and frustrating game at the same time

HRM, I play football with one all the time...

It's for level 19 by the way, the countdown one

12:21 PM

249 roubles for the game isn't much, but I'm still unable to afford that.

@zyabin101 Then you turn to searching for free downloads.

@zyabin101 Huh it costs 10€ (646 RUB) in France

At least on Steam

Hello all

Hello

After a lot of golfing, I finally finished my Jelly answer for my swap periodic challenge! codegolf.stackexchange.com/a/103888/47581

YES! \o/

It is done :D

12:29 PM

@StewieGriffin Wait, isn't the optimal strategy you cite for the free rules? See this PDF

TNB is invaded by darth vaders halp

2 hours ago, by Kritixi Lithos

So many Darth Vader hats in the chatroom.. (I'm looking at you @flawr with your oversized hat)

It may not matter though, since a time bound will make it infeasible. And now you know that about 254.59 is an upper bound for the score of any submission!

@TuxCopter *heavy breathing*

> Mod: Spammer, I am a mod
> Spammer: NOOOOOO

12:42 PM

I find your lack of faith...disturbing.

Dammit got ninja'd

@TuxCopter No... no, this can't be... no... no... NOOOOOOOOO!!!!ONE!!!ELEVEN

@TuxCopter Hm. Too bad mods and spammers are inherently antagonistic. It isn't really possible to tweak the "join me" line that comes afterward.

Join me, and together, we can rule TNB as mod and spammer.

:/

I am a spammer... like my modder before me...

Release that anger on the spam, Spammer, and your journey to the Modside will be complete!

Maybe it'd work better to flip the roles. Except for the power differential.

Q: The negative order integer challenge, but it's Prime Time!

12:52 PM

> Spammer: Mod, I am a spammer
> Mod: lmao
> *Spammer disconnected*

New Main Posts

0

Im talking about this question, take a look at it if you are a bit confused. Main Task Your task is to output integers, in decreasing order, but increasing the maximum integer everytime you hit 1 (for this question, 1 will be considered a prime number). While this doesn't sound any different fr...

code-golf sequence primes

Q: The strange ordering of Sharkovskii

@El'endiaStarman But "Modside" works better than "Spam side"...

@TuxCopter That last line should be replaced with "BAN HAMMER LUL"

Can't edit anymore

:(

:(

1:16 PM

0

Introduction In this challenge, we will be dealing with a certain ordering of the positive integers. The ordering goes like this: 3, 5, 7, 9, 11, ... 2*3, 2*5, 2*7, 2*9, 2*11, ... 4*3, 4*5, 4*7, 4*9, 4*11, ... 8*3, 8*5, 8*7, 8*9, 8*11, ... 16*3, 16*5, 16*7, 16*9, 1...

code-golf number decision-problem

@zyabin101 Yes let's do that. And let's not start something like this again.

Everyone: Be the smart one and don't participate in or escalate noise like this.

OK.

→ 12 messages moved to Trash

Checking timezone.... looks like it's late afternoon (~2) for Europe.

Exactly

1:19 PM

That's early afternoon in my book.

8 AM here

And that's early afternoon too

@noɥʇʎPʎzɐɹC Define 'here'

time.is

@TuxCopter where I live

@TuxCopter EST, I presume.

Yep.

1:21 PM

5pm for Saratov.

Is est the only timezone acronym that's also a latin word?

Wait it's called Eastern Standard Time but the America is at the west?

(Yup, the Saratovskaya region's time was shifted 1 hour later recently.)

compared to GREAT BRITANNIA it's east (/s)

@TuxCopter Huh? America is the center of the world.

1:22 PM

@TuxCopter You know that not all maps are eurocentric, right?

It's "Eastern" for the east coast.

@TuxCopter The Far East is west of America and the West is east of America

^^

America centric world map.

Also, is there an editor for the PNG binary format chunks?

Not an image editor, but an editor for the innards of the image.

1:24 PM

What do you mean?

Something less than an image editor but more than a hex editor? Or are you talking about the PNG header?

@mınxomaτ Kinda.

GIMP allows for exporting as PNG with some control over the format (whether to use Adam7 interlacing, gamma, compression level, and a few other things). Not sure if that relates to what you want.

Nah.

I'd need, for example, to write a tEXt chunk (to perfectly steganograph some text in the image).

Ah OK. I can't see an obvious option for that.

1:40 PM

:/

Do you mean adding text after the image data, or using the least significant bit of each pixel to encode undetectable data?

The former.

In that case would a standard text editor work? As long as you only append and don't delete anything

:/

code-golf array-manipulation 3d

@zyabin101 Works for me...

(just tried with Notepad++)

New Main Posts

1:52 PM

1

Q: Wrap a seasonal present

Given a wrapper element and a 3D array, wrap the array top, bottom, and all-around. Examples: Given the 2 layer, 2 row, 2 column numeric array [[[1,2], [3,4]], [[5,6], [7,8]]]` and the number 0, answer the 4 layer, 4 row, 4 column numeric array [[[0,0,0,0], [0,0,0,0], [0,0,0,0...

@trichoplax At the end of the file? Might be easier to just do that on the command line, e.g. echo Hello >> file.png.

Even easier. Thanks. I was trying for zyabin101 and I'm not sure the purpose behind it, so I don't know if ":/" means it isn't a suitable solution.

2:11 PM

@trichoplax Hm, seems to work. Thanks.

@zyabin101 See minxomat's even quicker suggestion too...

Okay. :3

I assume this is just for toy steganography? You're not putting anything confidential like bank details in there...?

That'd be a bit convoluted to use.

Well yes, but I was more concerned about the lack of security...

2:22 PM

do people here sort by activity or votes? (i do activity)

Sp3000

Activity almost always, oldest in a few rare cases

The only time I sort by votes is if I know I'm looking for something which was highly voted and there's too many to sift through

By oldest.

Activity

aloha

I have a very serious question that's been bugging me for days. what is "real estate" real in comparison to? what is "fake estate"???

@GabrielBenamy Not "real" as in "reality" but as in "fixed" -- english.stackexchange.com/q/66379

2:38 PM

well that's just disappointing

@TimmyD Any idea how you got that hat...?

I just noticed that I got it too. o.O

Friendly hug of death by Snapchat on NTP: news.ntppool.org/2016/12/load

I barely did anything other than voting on Meta and chatting...

I think it's their Solstice-related one this year. Meaning, participate on a site during the Solstice.

2:42 PM

how much rep do you need to vote to delete a post?

*an answer

@Flp.Tkc codegolf.stackexchange.com/help/privileges

Those numbers will change when we go through the graduation process.

A: Sandbox for Proposed Challenges

*if :P

thanks for the link

arda

@noɥʇʎPʎzɐɹC thanks :) here's the source with more characters in a similar style, if you want to check them out

mbomb007

@Dennis How is my answer different from the SQL answer, which stores data in a table?

New Sandboxed Posts

0

Rounding errors The task round down a number until it only has one significant digit. But every time a number gets rounded down more, make it choose wrongly to take the ceiling, or the floor. The output should have all the itirations of the rounding - input included. The format can be anything...

3:04 PM

Got a new hat

It's a secret hat. And for some reason I got it here and on English Language & Usage

New Meta Posts

1

Q: Serial voting on PPCG

I was reading What is serial voting and how does it affect me? on meta stackexchange, and I realised that when browsing through the recent code-golf submissions (as I do a few times a week) I often go through the posts and upvote good answers. A few people (Dennis, Martin Ender, Luis Mendo) provi...

support up-votes

@mbomb007 Data in a SQL table is persistent, though. Additionally, while REPL environments count as a language, they certainly don't count as a full program.

Similar to the PowerShell answer

@Sherlock9 The consensus seems to think this is the Solstice hat.

@Lembik GCC with -S compiles but doesn't assemble so you can see the assrmbly if that's what you mean

Oh, I have misread the conversation from earlier then

It is a very nice hat

I kind of wish I had a hat that wasn't a mask though. The horizontal eyeholes don't really fit with my "tilted head" profile picture.

I actually haven't gotten it yet. The hat drops seem to be very slow for me

3:11 PM

@quartata Go fight win!

2

Actually pretty interesting: Mark Zuckerberg built Jarvis.

Not the AI from Iron Man, but inspired by it.

@TuxCopter As someone who has worked in Ops, can confirm.

Got the Solstice hat. Man is it ugly.

I hope bluefeet isn't listening but if he is: I'm sorry I'm just super picky about hats

3:27 PM

We all got one more hat

@El'endiaStarman Well, Jarvis is just an acronym. Lot's of AIs can be jarvis.

I earned Where in the world

I'm already getting quite accustomed to my TNB Grinch role

We all earned the trophy a few minutes ago in PPCG

Good news guys: The community has got 20 different hats! Now, if you haven't got any hat yet, go to vote correctly on a post on meta. You will get the Darth Vader hat. If you have a hat, you should have already got the Trophy hat on PPCG.

3:33 PM

I had no idea it would be so easy to get hats by accident. I guess this is the first year I haven't tried to get hats

I'm using the trophy as a makeshift yarmulke

Well, the trophy base anyway. The gold trophy top kind of stands out

haha

Also, it's a little difficult to balance :P

Yeah, that's the issue with hats.

DJMcMayhem

I went to try to get hats but I'm way too busy. :/

3:37 PM

Lol you are a cat in a hat!

I also have a question: How do you 11 your name?

cmc: i'm tired of everything being christmas, do a hanukkah thing

@GabrielBenamy Closed as too broad.

@ErikGolferエリックゴルファー I think that would currently earn you three hats, counting "Where in the World?"

How do you win Where in the World?

I had it but idk why

I don't want to discuss about secret hats.

3:48 PM

@TuxCopter Do anything during the next 19 hours or so (while it's December 21 anywhere in the world)

Eh shouldn't Solstice be earned at the 21?

Q: Festival of ASCII-art lights

9

Write, in as few characters as possible, a program that takes zero or six command-line arguments menorah menorah YEAR MONTH DAY HOUR MINUTE SECOND (Both forms must be supported. The zero-argument version shall be equivalent to calling the six-argument version with the current system date and ...

code-golf ascii-art date

Not 19 hours actually, 43. I forgot it's not the 21st yet in most of the world

@TuxCopter To paraphrase Jimmy Buffett, "It's the 21st somewhere."

4:06 PM

Idea for a hat-themed challenge: Given a string of ASCII chars, give all vowels hats (i.e. circumflexes)

That may be too regex-reliant to make an interesting challenge though

@ETHproductions Duplicate

Hmm, how did I miss that challenge?

Or maybe count the number of circumflexes in a given input string

:D

I obtained "Just Here for the Hat"! :D

Time to invent a new algorithm in COW

@GabrielBenamy COW?

@Qwerp-Derp I have posted an idea in the Fourtune room. Check it out?

4:20 PM

@zyabin101 web.archive.org/web/20130403133623/bigzaphod.org/cow

@ETHproductions Like, how many characters in âĉêĝĥîĵôŝûŵŷẑ are there in a string?

Dennis

@Zgarb Speed very much depends on how many users are trying to access the server at the same time.

@ErikGolferエリックゴルファー Yeah, including uppercase

Oh, so ^ is not included.

Oh, good point....

4:23 PM

Yeah, you can't do it too easily in Jelly.

Haha, just edited one more question's tags and earned the taco hat

How do you get the Taco?

Oh, so taco is for editing tags? Wow, I'ma edit some tags now, non-abusively.

@KritixiLithos They say it has something to do with short edit messages

Several people have earned it just by editing tags on multiple questions

A: Sandbox for Proposed Challenges

Well, edited tags is just 11 chars. Oh great, ~~I'ma make a pointless edit on one of my posts with the edit summary abcdefghij~~ I am afraid of Dennis' trout.

New Sandboxed Posts

4:25 PM

1

Golf a Numerical Growing Braid (not Pascal's) Braid Description In this braid, when a strand crosses over the top of another strand it adds the other strand's value to itself and all other strand values pass through. The braid has three strands and each strand begins at 1. The first crossover i...

@ETHproductions How many times have you edited tags?

Tag Aand Comment Only, maybe?

@KritixiLithos I did five last night (which earned me Sherlock for editing 5 posts 3+ years old) and one just now

I know there exists a BF algorithm to do this, but I wanna see if I can figure it out.

Or maybe edit without commenting or answering?

DJMcMayhem

4:28 PM

I just got a secret hat without doing anything. 0_0

My Unipants blueprint is now put on a wall. :3

I don't think that 1) aand is word 2) and counts as a word in acronymification.

@DJMcMayhem Where in the World? is earned by doing anything while it's Dec 21 somewhere

It seems to, at least, with the "Just Here for the" hat.

@ETHproductions Hey, you spoiled it ;_;

@ErikGolferエリックゴルファー It's the aardvark "aand." :p

4:30 PM

@DJMcMayhem Where in the world did you earn it??? I wanna know.

yay, the hats are gone!

Aardvark

The aardvark (/ˈɑːrd.vɑːrk/ ARD-vark; Orycteropus afer) is a medium-sized, burrowing, nocturnal mammal native to Africa. It is the only living species of the order Tubulidentata, although other prehistoric species and genera of Tubulidentata are known. Unlike other insectivores, it has a long pig-like snout, which is used to sniff out food. It roams over most of the southern two-thirds of the African continent, avoiding areas that are mainly rocky. A nocturnal feeder, it subsists on ants and termites, which it will dig out of their hills using its sharp claws and powerful legs. It also digs to...

huh?

@TuxCopter I aaccidentally doubled up on the leading "a".

DJMcMayhem

@ETHproductions Oh. Well that's boring

winter: bashed
hats: deleted
site: logged-in

_i forcibly opt-out of the festivities_

4:33 PM

Lol you bashed Mother Nature.

Congratulations to @KritixiLithos who has 3k rep!

3

@betseg Thanks for noticing!

@GabrielBenamy No!

Is anyone here really good at list operations in python? I need some help with golfing this answer

Why'd you hate hats? :'(

4:35 PM

Yay, and I also got the code-golf bronze badge!

@KritixiLithos i got it just an hour or so ago! woohoo

I searched for "mandelbrot" and found this:

ams.org/mathimagery/displayimage.php?pid=458

7

:D

"a pancake by Nathan Shields"

The link also has lorenz attractor, pythagorean tree, and sierpinski sieve...

4:40 PM

That's quite a creative form of art

Okay, maybe BF doesn't have an online algorithm for this.

If the language is turing-complete, there must be a way to tell whether a number is positive or negative.

I like that the taco doubles as a sombrero:

Suits you

pretty neat

Then I am the highest hat person in PPCG who doesn't wear a hat

4:44 PM

Guys, stop bumping ancient questions just for hats

2

It's not an abuse of privileges it's just annoying

I wouldn't mind if it was just one person but half of the questions on the front page are from 2012

I'm not trying to get hats, I'm just wearing hats that are available, and I have 4 hats.

um... I just got a +1 rep, and when I clicked on it, there was nothing new in the box?

Means an answer you downvoted was deleted

I wonder what differentiates between the sun and moon hats

Riley

@GabrielBenamy You could make two copies. Then add 1 to one of them and subtract 1 from the other, and see which one reaches 0.

4:50 PM

@Riley That could work. If the strategy I'm trying doesn't pan out, I'll give that a try.

@ETHproductions Probably nothing. Like The Dress from last year.

Dennis

@mbomb007 I don't know SQL (at all), but I'm assuming SQL tables persist between runs. There are a few JavaScript answers as well, but those use localStorage.