The Nineteenth Byte

Prime Factorial code-golf math number For the purposes of this question, the prime factorial of a number n is the result of multiplying all prime numbers smaller than n, and then multiplying the result by n. Your Task: Write a program or function to find the prime factorial of a number, as o...

New Main Posts

12:16 AM

2

Q: BIU numbers (or Sumdivized numbers)

How to spot them Take a positive integer k. Find its divisors. Find the distinct prime factors of each divisor. Sum all these factors together. If this number (sum) is a divisor of k (if the sum devides k) then, this number k, is a BIU number Examples Let's take the number 54 Find all the ...

Adám

@HyperNeutrino CP858 gets rid of most box drawing chars in favor of accented Latin.

HyperNeutrino

@Adám Ooh I might consider this one :D Thanks!

New Main Posts

12:32 AM

0

Q: Answer chain the English Alphabet!

In this answer chaining challenge, you will work together to figure out how to output all the 26 letters of the English alphabet! How does this work? For each answer, you must pick a new language (or a new major version of a language, for example, python 2 and python 3 are counted separately) t...

alphabet answer-chaining

Mistah Figgins

12:48 AM

how do you do tags in comments?

I tried [tag:polyglot] but it sent me to the tag of "tagpolyglot"

really? polyglot

Comments != chat

ok

Also, I don't think you can tag in comments.

Pavel

mebbe [polyglot] ?

SE has three different markdowns and it's annoying af

Mistah Figgins

12:50 AM

@Pavel yeah

I fixed it by doing normal linking

ATaco

Markdown is annoying, and makes my CMC TIO userscript not work in all cases.

Mistah Figgins

@Pavel that just does [polyglot] in plaintext

Destructible Lemon

ok I forgot to use the sandbox

HyperNeutrino

lol I was trying to list all characters that my phone could type and guess which one I missed

Pavel

@ATaco Right, but you can build edge cases into your script to account for that.

Downgoat

12:59 AM

Question: what does magenta highlight mean in git commit diffs?

^ picture

Pavel

Maybe there wasn't whitespace before, and now there is?

Destructible Lemon

is it whitespace but different type of whitespace?

Scrooble

The XKCD space -> spaaace replacement is making this fun to read.

Downgoat

@DestructibleLemon yea I think that was it, it seemed to be a tab (blame nano)

Destructible Lemon

I did it

in return, please send your bank account info pls /s

Christopher 2EZ 4RTZ

1:03 AM

@Downgoat amazon.com/GoatMan-Took-Holiday-Being-Human/dp/1616894059

2

Downgoat

@DestructibleLemon dont have credit card is ssn ok?

Destructible Lemon

no

Christopher 2EZ 4RTZ

@Downgoat I need copy to, need to file invoice

btw downgoat do click that link

Destructible Lemon

you could instead choose to help me make my koth thing?

pls

Christopher 2EZ 4RTZ

@DestructibleLemon you should learn to do it on your own time

Destructible Lemon

1:07 AM

I need a second opinion thing or something

Christopher 2EZ 4RTZ

Ok i give

for SSN

super sweet number

Downgoat

Question: why can I not do: echo "${$@:1}"

Destructible Lemon

ok so can we post not particularly on topic strawpolls things?

Christopher 2EZ 4RTZ

Yeah

Destructible Lemon

ok I would post but strawpoll.me is not working for me

Mistah Figgins

1:24 AM

strawpoll.me/14019655

excuse me?

HyperNeutrino

wtf I have 444 Facebook notifications?

Mistah Figgins

I broke it

Destructible Lemon

it's sort of working

Mistah Figgins

Is anyone else having problems?

whenever I type, it goes to the top of the page...

MD XF

@MistahFiggins >.<

Mistah Figgins

1:26 AM

and are there 2 strawpoll oneboxes for anyone else?

Ok i fixed it

I think I had 2 userscripts doing the same thing

HyperNeutrino

is strawpoll oneboxing by taco or normal?

Mistah Figgins

i think the answer is yes

HyperNeutrino

huh?

Mistah Figgins

meaning both

HyperNeutrino

are you doing the a or b = yes logic prank on me

@MistahFiggins oh ok

ಠ_ಠ then just say both

Mistah Figgins

1:28 AM

sorry

HyperNeutrino

:P

Mistah Figgins

this is what it looked like at the top of the page

there were also 2 messages by me with the poll

Destructible Lemon

ok so should my koth limit the speed of bots, and should it limit range of sight?

ATaco

Strawpoll oneboxing is taco.

And that double onebox is a known bug.

HyperNeutrino

ah ok

New Sandboxed Posts

1:32 AM

0

A: Sandbox for Proposed Challenges

Output an Anagram! No Not That One! code-golf anagram string Given a unique list of strings that are anagrams of each other, output an anagram of those words that is different from each word in the list. The strings will be alphanumeric, and there is guaranteed to be a valid anagram. Test Cas...

HyperNeutrino

brb o/

Mistah Figgins

no, they were backwards

Destructible Lemon

weird chat things

Mistah Figgins

I would type something, and it would go to the very top

Destructible Lemon

oh

Mistah Figgins

1:33 AM

it's all good now

Destructible Lemon

most strange

Mistah Figgins

and it was all client side anyways

@DestructibleLemon yes, very

Christopher 2EZ 4RTZ

@MistahFiggins Mine did that

Destructible Lemon

@ATaco team spirit hasn't been working for a while

ATaco

I know the problem, I just haven't gotten around to patching it.

I'm a busy Taco.

MD XF

1:40 AM

Whoa @KennyLau how come you changed your name back?

ATaco

@cairdcoinheringaahing Lua, 11 bytes string.gsub

Nick Clifford

@cairdcoinheringaahing Ohm v2, 1 byte \

ATaco

\

Nick Clifford

\

ATaco

Two backticks, a backslack, two backticks.

Nick Clifford

1:49 AM

thanks

HyperNeutrino

> backslack

@MDXF bugs (something to do with his other account name overriding Leaky Nun)

\

MD XF

Weird

HyperNeutrino

huh interesting

ATaco

Rename KennyLau KennyLua when?

HyperNeutrino

ಠ_ಠ

Nick Clifford

1:54 AM

is backslack when you move your team to some other platform but then realize you like slack better so you move back to slack?

HyperNeutrino

sure

Nick Clifford

i'm a comedy genius, trust me

HyperNeutrino

sure

Christopher 2EZ 4RTZ

running star citizen is hard :P

Destructible Lemon

ok so what language do I make my koth in, anyway? if I choose python, very few people will consider playing

I could try the new lang idea

maybe I'll just make some sort of forth-y thing

Christopher 2EZ 4RTZ

2:03 AM

make it so it supports all languages

Destructible Lemon

no that is laggy

HyperNeutrino

laggy < no answers

just leave it running overnight

Destructible Lemon

too laggy

way too laggy

like even with bots doing literally nothing but returning a constant it lags

actually forthy things might be annoying to program

I'm not entirely sure what paradigm my language will be tbh

Christopher 2EZ 4RTZ

Don't tell me about lag

I am running star citizen

Destructible Lemon

I reckon it will be imperative actually

yeah I'm gonna make a custom language unless that turns out to be laggier somehow

HyperNeutrino

2:11 AM

I decided to reconsider my life choices after getting almost 350 rep on SO yesterday

Christopher 2EZ 4RTZ

In star citizen i just shot a window out and jumped into space, I then flew through space with my rockets and on the move took out another window and ninja rolled in jumped a balcony and kept going

Anonymous

@HyperNeutrino Congrats in advance for getting almost 350 rep on PPCG today

Christopher 2EZ 4RTZ

This is the best game

HyperNeutrino

@Mego :P thx but not gonna happen :P

1. I'd need bounties and I've gotten like a grand total of 2
2. Or, I'd need accepts and good luck with that on PPCG

The only reason I managed to get over 200 (way over 200) was because like 10 accepts :D

Christopher 2EZ 4RTZ

PPCG accepts?

HyperNeutrino

2:14 AM

nope

that's why

I've gotten like 2 accepts maybe? not much more than I have bounties

Destructible Lemon

actually I just remembered I don't really know how to make parsers and stuff

HyperNeutrino

rip

Destructible Lemon

I made a lisplike interpreter thing once

HyperNeutrino

I've made two different parsers but don't ask me for help or you will end up a terrible programmer

Christopher 2EZ 4RTZ

I have no accepts, but I have the shortest solution on a problem

Destructible Lemon

2:17 AM

so I guess the language might be like that

HyperNeutrino

ppl pls answer

130

Q: "KNOT" or "NOT"?

Write a program that processes an ASCII art representation of a tangled string and decides whether or not it can be untangled into a simple loop. The tangle is represented using the characters - and | to represent horizontal and vertical segments, and + to represent corners. Places where the stri...

code-golf ascii-art decision-problem knot-theory

I has bounty you can get :3

Anonymous

I'm surprised nobody has attempted this bounty yet

Destructible Lemon

I don't know knot theory without it being in a program

@Mego tbh it's more surprising it hasn't been closed

HyperNeutrino

CJam looks like it has many braces

GS seems to have many numbers

Pyth seems to have many capital letters

Destructible Lemon

you also have to consider cases which are none though

HyperNeutrino

2:24 AM

yeah

ATaco

That bounty is far too difficult for me.

Destructible Lemon

vtc unclear /s

ASCII-only

@HyperNeutrino It's very nontrivial isn't it

Funky Computer Man

Anyone up for some contact?

ATaco

Always.

HyperNeutrino

2:29 AM

@ASCII-only yes

nvm I would play but I have like 3 mins

ASCII-only

@Mego I'd do it but too lazy to make a spec of the syntax for each language, and I can't find it anywhere

@HyperNeutrino I don't think many could do it in just 4 days

HyperNeutrino

yeah I maybe should've added to the infinite bounties

but I mean mostly if nobody else makes an answer I was initially planning on just awarding the existing one but I thought to give everyone a chance so I specified as such :P

Funky Computer Man

The Mini-Flak indefinite bounty is not very hard and its worth 1000, just saying

Anonymous

@ASCII-only All 3 of them are on TIO. All you have to do is click the name of the language on their TIO page to go to the repo, then go to the docs.

Anonymous

In fact, with TIO, the challenge is much easier - I had to download and set up all 3 languages when I wrote my answer.

HyperNeutrino

2:37 AM

gtg now anyway, cya! o/

DJMcMayhem

@FunkyComputerMan That isn't very reassuring coming from the master of brain-flak :P

NMP incoming

ASCII-only

@Mego Well yes but I want complete syntax not docs :P

It's possible rn but you'll have to read through all the docs and I'm too lazy to do that :P

Anonymous

@ASCII-only The syntax is simple and the docs teach you. Pyth is a prefix language, and CJam and Golfscript are stack-based.

ASCII-only

Yeah I know >_> I meant for this you don't need to know what they do, but I guess the CJam (?) cheatsheet lists out all the functions/operators anyway

New Main Posts

1

Q: The Three 'R's: Reverse, Reorder, Repeat

While doodling around with numbers, I found an interesting permutation you can generate from a list of numbers. If you repeat this same permutation enough times, you will always end up back at the original array. Let's use the following list: [1, 2, 3, 4, 5] as an example Reverse the array. ...

code-golf array-manipulation

Destructible Lemon

2:55 AM

hey what if I try and make a silos derivative for my koth challenge?

actually now that I think about it there's like java vm stuff involved there or something

Maltysen

@Mego gonna try it maybe

Leaky Nun

5:12 AM

@MDXF I didnt; hopefully it will have been fixed by now

yes, it is

Alex K Chen

Can someone give motivation why should I use class in python ?

ATaco

In golfing or in actual pythonics?

Alex K Chen

In actual python.

I mean, class doesn't adds any functionality, does it ?

ATaco

It's best if you want to write code that's easier for other people to understand.

You can overload operators and such, and instance it obviously.

ASCII-only

@AlexKChen You don't have to

Alex K Chen

5:19 AM

No I mean say only I use the code, but the code does use using a same thing. Is class natural to use here? (Will I show you an example ?)

ASCII-only

@AlexKChen You don't have to

But when you want multiple things to behave similarly, classes are very useful

Alex K Chen

OK, I'm giving you an example.

ASCII-only

@AlexKChen You don't have to

But when you want multiple things to behave similarly, classes are very useful

Destructible Lemon

I wrote something that only gets used once and I think I recall @ASCII-only bothering me to use a class...

ATaco

Classes are absolutely unnecessary, if that's what you're asking.

But they're unnecessary in C++ too.

Destructible Lemon

5:22 AM

in terms of turing completeness and functionality (like bonus non-tc stuff like i/o and graphics and such), yes they are unnecessary

also it prevents people complaining about global variables?

Leaky Nun

@AlexKChen can I rant about finite fields?

Alex K Chen

@LeakyNun "rant" ?! (Of course go on :P )

@LeakyNun You probably messed up the two rooms right :P ? This is TNB lol

ATaco

Screams in mathematics

Alex K Chen

(No well Mego cares he kickmuted me lots of times for discussing off topic tasks)

Leaky Nun

@AlexKChen go there then

ATaco

5:32 AM

I am so incredibly tired.

Adám

CMC: (OOP langs only) create a class.

Destructible Lemon

this works in python? class x:pass

Leaky Nun

@Adám class x:0

Destructible Lemon

yeah I guess that works too

ATaco

Java, 9 bytes class c{}

Destructible Lemon

5:39 AM

however the codegolf criteria was not specified

so there

Adám

@ATaco Java ties Python.

@DestructibleLemon What do you mean?

ATaco

Describe, "Class"

Leaky Nun

it's codegolf by default @DestructibleLemon

Destructible Lemon

technically you said create a class without mentioning size

ATaco

C, 9 bytes struct{}; (Depending on your definition of "Class")

Adám

5:42 AM

@ATaco That's not a real class. C isn't an OOPL by default. Try C# or C++.

Destructible Lemon

magic number 9?

Adám

@DestructibleLemon APL is incredibly verbose on this one.

ATaco

Hence i said, depending your definition of class...

Adám

@ATaco Hence I answered…

ATaco

C++ needs 10 bytes, class c{};

Sadly you can't have an unnamed class.

Adám

5:45 AM

@ATaco Can any language?

ASCII-only

@ATaco well obviously >_>

ATaco

Well if struct counted as a class you could, however you seem to firmly believe it does not.

ASCII-only

@Adám There's really no benefit in unnamed classes, they're pretty much always something you instantiate

And without a name you can't really do that

Adám

@ASCII-only Right. APL also requires classes to be named, although namespaces (think JSON objects) can be unnnamed.

ATaco

There is a few reasons, but they're not really good ones.

Adám

5:47 AM

@ASCII-only Couldn't you use a reference instead of the name?

ASCII-only

@Adám well yeah but isn't reference = variable (basically a name) anyway :P

ATaco

Lua, 2 bytes. {}.

Kind of.

ASCII-only

Also classes need to be compile time for compiled languages (well at least the ones with overloads) so no references I think?

Adám

@ATaco Does that have any OO properties, or is it just a simple object?

ATaco

Kind of?

You can supply metamethods and such: {__add = function(a,b)print(a,b)return 0 end}

However, these classes are applied to objects, rather than instances being spawned off them.

setmetatable({}, your_class_here)

Adám

5:51 AM

@ATaco Sure, OK, but can anything be hidden when seen from the outside due to being private?

ATaco

If you know what you're doing, definitely.

Adám

@ATaco Applied to objects? No instances? Sure sounds very different from C# style OO…

ATaco

It is definitely a stretch.

But functionally, it's identical to something like a JavaScript prototype.

ASCII-only

It isn't a class at all...

ATaco

Hacky privates

Worth a shot.

Adám

5:56 AM

And now, for the most verbose (?) of them all, Dyalog APL, 26 bytes: ⎕FIX':Class c' ':EndClass'

ATaco

Lua, despite having a chapter on classes says it doesn't have classes, but it can emulate them.

Alas, rest in piece the 2 byte class definition.

Adám

CMC: Given a class (or the name of a class or a reference to one, etc.) return an instance (ir its name, or a reference to it) of said class.

ATaco

C++ (gcc), 20 bytes #define i(c) new c()

Preprocessor solution anyone? :P

C++ (gcc), 19 bytes #define i(c)new c()

Wasted whitespace is sin.

Adám

@Adám Dyalog APL, 4 bytes: ⎕NEW

Oh the irony: a tacit (points-free) functional way of creating an instance of a class…

Alex K Chen

6:17 AM

OK, so should why should I use class in python ?

Adám

6:30 AM

@AlexKChen Nobody is forcing you to.

Alex K Chen

Ya I know, but they say you should use them for elegance as usefulness and mental chunking and what not. is it so ?

Adám

@AlexKChen No. It is a matter of style and taste. Some people prefer abstraction through OO, some people prefer purely functional programming.

Alex K Chen

Do you know about finite fields (or, primitive roots) so that I can show you an example code using those and if you can tell how to improve that using class (in python)

New Sandboxed Posts

7:20 AM

0

A: Sandbox for Proposed Challenges

It’s raining numbers! Better to get a good umbrella! code-golf ascii-art Your task is to take in one integer input and print a “raining” alternating pattern with that number, and an umbrella of appropriate size to protect yourself from such a rain! Examples 1 _|_ / \ ----- | C 2 ...

flawr

7:52 AM

@AlexKChen I can try if you want, my python is probably a bit rusty.

@HyperNeutrino basically you consider the usual polynomials, but your calculate "+" with "min(,)" and "*" with "+".

flawr

8:14 AM

So e.g. 3x^2 + 5 would actually be evaluated as min(3+2*x,5)

Leaky Nun

8:27 AM

@flawr I wouldn't use * here: 3x^2 + 5 = min(3+x+x,5)

The tropical semiring (ring without additive inverses) is a semiring $\langle \Bbb R \cup \{\infty\}, \oplus, \otimes \rangle$ with $x \oplus y = \min(x,y)$ and $x \otimes y = x+y$.

flawr

9:56 AM

brb inventing the arctic semiring.

Leaky Nun

@flawr lol

flawr

oh it already seems to exist

Leaky Nun

what the hell

flawr

The natural number with +infinity under the max (as sum) and + (as product) operations

ah, it makes sense as the tropical semiring is sometims also referredt to as the natural number with min and +.

borign

Leaky Nun

From marcpouly.ch/pdf/internal_100712.pdf

orlp

10:00 AM

I know it doesn't, I just wanted to see who else knew. — mathreadler 1 min ago

bullshit!

Leaky Nun

@orlp right

orlp

oeis.org/A000040

why is this not A000001?

Leaky Nun

> (Formerly M0652 N0241)

@_@

John Dvorak

It's getting there

flawr

@orlp Why is A000027 not A000001???

orlp

10:03 AM

@flawr fair enough

John Dvorak

The actual A000001 is ... less fun.

flawr

@JohnDvorak It is fundamental :D

John Dvorak

Fine then. Write a function that computes it.

flawr

wouldn't it be boring if they wasted A000001 to something trivial?

@JohnDvorak it is not that difficult - what would be more interesting is writing an efficient function

Leaky Nun

CMC: Number of Abelian groups of order n

[it isn't hard]

@flawr

Emigna

10:53 AM

@LeakyNun totally wrong. nwm

Probably missing something obvious

Leaky Nun

@Emigna 05AB1E has no partition @_@

Emigna

Not that kidn (afaik)

Fixed at 15 bytes: ÓεDÝDgã€{ÙOQO}P

Might be a better way to get the partitions, but this was the first I though of

In Jelly it should be just over 6 bytes. Unfortunately I can never figure out how to link stuff together properly

Ven

For [fastest-code], does compile-time count?

Leaky Nun

@Ven I don't think so

Ven

...So a challenge could be implemented at compile-time via metaprogramming?

Emigna

11:07 AM

There's probably some rule about doing work in preprocessing or soemthing

Ven

also CTFE

Emigna

Pretty sure there is a disallowed loophole regarding that

Anonymous

@Emigna I proposed one a while back, but it's been controversial.

Emigna

@LeakyNun Jelly 7 bytes: ÆEŒṗL€P

Leaky Nun

@Emigna nice

Emigna

11:12 AM

@Mego Interesting

Adám

12:15 PM

@Lembik Your wait is over.

@Lembik Notable that no-one noticed that the only example given was wrong.

New Main Posts

0

Q: Creepy Corridors

This challenge is inspired by a board game I played some time ago. The story of this challenge doesn't necessarily have to be read, the goal of the challenge-section should explain everything necessary. The Story People are locked inside a large room with a human-devouring monster. The walls of...

code-golf

Anonymous

12:45 PM

→ 1 chunk of processed meat moved to Trash

Lembik

@Adám oops.. is that my example which is wrong?

Adám

@Lembik I edited it for you.

Lembik

@Adám thanks!

your answer looks awesome and incomprehensible by the way :)

I want to pose a communication complexity puzzle but it seems this has never been done before on PPCG that I can see

Adám

@Lembik Oh dear. I thought my explanation broke it down in edible chunks. Which part is hard to understand?

Lembik

no you did a great job ... "ɩndex selfie of X" .. that' already mysterious to me

even the first line "Takes X as left argument and Y as right argument." The question doesn't talk about right and left arguments

but I can guess from the TIO example

"enclose to we can look for that entire pattern" What does "enclose to" mean?

Anonymous

12:51 PM

@Lembik It's a dyadic function. Dyads in APL (like in Jelly) take arguments from the left and the right.

Adám

@Lembik 'abcd' ⍳ 'abca' looks for the first occurrence of each letter of abca in abcd. ⍳⍨ 'abca' looks for the first occurrence of each letter of abca in itself.

Lembik

ok

Adám

@Lembik typo. fixed. thanks. ("so")

Lembik

why do you write ɩndex ?

instead of index?

Anonymous

@Adám So f⍨ a is functionally identical to a f a, modulo the different rules for monads and dyads?

Lembik

12:54 PM

@Adám It would help if you added at the start which algorithm you were implementing

Ven

@Mego yeah. for dyads, ⍺(f⍨)⍵ means ⍵f⍺

Anonymous

Good to know

Adám

@Lembik to indicate that ⍳ is mnemonic: ⍳ is Greek Iota ≈ Latin I as in Index.

Leaky Nun

CMC: write a function that when given two natural numbers x and y, return whether x<=y, where <= is an ordering on the natural numbers such that the order type of the natural numbers become $\omega^\omega$

Lembik

does ⍳⍨⍺ start with Iota too?

they look different to me

Adám

12:55 PM

@LeakyNun -1 for mathjax

Leaky Nun

@Adám :c

Lembik

we just need a nice easy link to mathjax here

for people who like to copy and paste

Adám

@Lembik In the code I use a Unicode APL Iota, in the description I use Unicode Greek Lowercase Iota.

Lembik

I mean what that thing is that you have to run to be able to see it in your browser

@Adám ok so that's just confusing

but I am sure APL lovers will love it :)

Adám

@Lembik It is because the fonts are not so well designed. The Greek one looks nice with Latin letters, while the APL one is positioned/sized wrong: ⍳ndex versus ɩndex

Lembik

12:57 PM

@Adám what was wrong with the answer "abda" that you edited?

Adám

@Lembik It isn't the first substring of matching pattern/

@Lembik abda stands out as obviously analogue to adca, so I assume you missed the fact that your (probably random) letters caused a pattern to occur 1 char earlier, namely dabd.

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