The Nineteenth Byte

Cows quack

8:04 AM

@ASCII-only what

user202729

@ASCII-only Use "3×7≡1 (mod 10) ⇒ 3×7p≡p (mod 10p)`

ASCII-only

@Cowsquack wait. no

user202729

Or sth like that.

Cows quack

@user202729 yeah that makes sense now

ASCII-only

@user202729 @Cowsquack well it's actually divided by p (i'm just bad at reading) so i have no idea what i'm saying

hang on. what

~~i'm confusing myself. how did i even get that equation~~ nvm

Cows quack

8:07 AM

wait I misread too

ASCII-only

i'm just going to ~~replace~~ cool off my brain for a bit

Cows quack

@ASCII-only I forgot about this

ASCII-only

so the latest correct equation appears to be d = (3-n³)÷(7p) (mod 10p) (i messed up here too) (well actually I'm pretty sure user202729's equation can actually apply here. so we have -n³÷p÷7 (mod 10p) and we want 7n³÷p (mod 10p)

Cows quack

@ASCII-only n=587;p=1000;((3-n**3)/(7*p))%(10*p) gives 1105 wat

ASCII-only

@Cowsquack hang on. d is supposed to be from 1 to 9

idek what i'm even doing anymore

user202729

8:22 AM

@ASCII-only 0 to 9.

ASCII-only

@user202729 oh yeah

@Cowsquack so actually it should be mod 10 since we already divided by p

Cows quack

which still doesn't work

it doesn't give 4

user202729

@Cowsquack Because....

ASCII-only

@Cowsquack well actually. it's supposed to be modular division. so yeah vv should work. if it doesn't then i messed something up really bad

user202729

you're not supposed to divide by 7.

Multiply by 3 please.

Cows quack

8:28 AM

o_O

Mar 24 at 15:47, by user202729

(as F_p is a field, dividing 1 by 2 automatically produce the inverse of 2 modulo p, anyway...)

user202729

But Python is not a field.

ASCII-only

^. python doesn't have modular division operator

user202729

Yes.

Cows quack

chat.stackexchange.com/transcript/message/43590083#43590083 then why do you divide by 2 here

I am confused

ASCII-only

@Cowsquack p is a prime greater than 5. i.e. p+1 is even

Cows quack

8:37 AM

oh so the division by 7 doesn't work because 7 ⌿ (3-n**3)/p

ah so that's also why you can divide by p

(even though there is no inverse of p mod 10p?)

user202729

Question: Do I need npm if I have pnpm?

ASCII-only

@user202729 no

@user202729 pnpm is a drop-in replacement

pretty sure it uses the npm registry (unlike yarn)

user202729

What if something complains about "npm not found"?

(symlink npm to pnpm is an option but...)

ASCII-only

@user202729 alias maybe?

but yeah symlink is probably the best idea

user202729

Anything requires -g also requires sudo, right?

ASCII-only

8:53 AM

@user202729 pretty sure. since it installs things in /bin i think?

(does installing something in /usr/bin not require sudo)

user202729

Ok, sudo ln -s /usr/bin/pnpm /usr/bin/npm. Hopefully doesn't cause infinite loop or something.

> Other commands are passed through to npm

(from pnpm help)

Not sure if it's a good or bad idea. I'm just following tutorials that uses npm.

ASCII-only

@user202729 :| rip

Cows quack

@ASCII-only I think when you divide by p, you also divide 10p by p (inside the mod) to get -n^3/7p (mod 10), then you can do modular inverse of 7 is 3, blah blah, and simplify it further to 7*n^3/p (mod 10)

that is how you end up with mod 10

(the above was a guess at my part)

ASCII-only

@Cowsquack ah. makes sense

Cows quack

nice answer btw

ASCII-only

9:02 AM

@Cowsquack if you're talking about what we were trying to figure out then i found it 100% by accident

Cows quack

@Cowsquack I guess (?) the reason you divide the 10p inside the mod by p is that you cannot simply divide by p as you said (no modular inverse for p mod 10p)

nice accident then :P

New Meta Posts

9:30 AM

0

Q: Invalid answers in the review queue, but OP hasn't had time to fix it

It happens quite frequently that short answers (Title + Code) appear in the Low Quality review queue, due to the automatic flagging mechanisms. In most cases, the answer "Looks OK". However, there are cases where the answer was posted in good faith, but the output in some scenarios are incorrec...

user202729

So does pnpm need /lib/node_modules?

user202729

9:51 AM

It doesn't.

betseg

10:18 AM

johansen.software/github-xp

ASCII-only

@betseg this... is ridiculously terrible

New Main Posts

10:43 AM

0

Q: Find the 10-adic cube root of 3

I like to think of a 10-adic number as a number that goes infinitely to the left, or an integer modulo a very very large power of 10. Things carry infinitely to the left and vanish. To see what I mean, note that ...6667 * 3 = 1 in the 10-adic land, since the "2" that carries to the left goes to ...

code-golf number-theory

user202729

@LeakyNun No time limit? ...

@ASCII-only You may want to post your Python solution.

ASCII-only

@user202729 yep, doing now

user202729

Hm...

An easy one.

ASCII-only

?

user202729

So perhaps I can use some esolangs.

ASCII-only

10:52 AM

yeah

I wonder if it's possible to calculate the nth digit without using all digits before it

user202729

@ASCII-only input()-1 please

ASCII-only

@user202729 oh. oops

user202729

...

Or just n%p.

Actually either way have the same bytecount.

With ~-.

Leaky Nun

@user202729 sorry, forgot

user202729

@ASCII-only Consider adding explanation?

ASCII-only

10:56 AM

@user202729 i don't exactly know how it works still >_>

user202729

:/

Leaky Nun

-,- I went to shower

do you guys

FrownyFrog

we do us

user202729

@ASCII-only But then... do you just randomly try formulas till they work or...?

ASCII-only

@user202729 nah. i listed out n and n**3 until i found a pattern (same with the one before this)

Anush

11:19 AM

hi all

OT again.. but I can't work out how to compile github.com/cheind/inpaint and it is driving me crazy

user202729

What's the errors?

Anush

I think I might have worked it out.. 1) cmake .

this wasn't described anywhere

ASCII-only

@Anush what?

Anush

2) realise you need to do sudo apt-get install libopencv-dev

@ASCII-only you need to run cmake first it seems

ah no.. still fails :)

ASCII-only

> To build Inpaint from source you need the following prerequisites

CMake - for generating cross plattform build files
OpenCV - for image processing related functions

...

it says you need opencv

Anush

11:22 AM

right but what do I actually type on the command line once I have those

ASCII-only

should just be cmake or something

@Anush how exactly does it fail

user202729

Try reading the documentation of cmake?

Anush

@ASCII-only cmake on its own doesn't work. I did "cmake ." which seems to work

then I did "make"

/home/user/inpaint/tests/patch_match.cpp: In function ‘void ____C_A_T_C_H____T_E_S_T____48()’:
/home/user/inpaint/tests/patch_match.cpp:55:43: error: ‘FILLED’ is not a member of ‘cv’
cv::rectangle(mask, r, cv::Scalar(0), cv::FILLED);
^
CMakeFiles/inpaint_tests.dir/build.make:182: recipe for target 'CMakeFiles/inpaint_tests.dir/tests/patch_match.cpp.o' failed

and it fails with

user202729

What?

But it...

Anush

that's the error message from make

user202729

11:25 AM

read cv docs

cv or cv2?

Hm...

Probably you need a suitable version of cv.

Anush

hmm

I feel a whole new sort of challenge.. how quickly can you compile this piece of open source code :)

Bora Calim

compiling open source stuff is really hard

for mortals like us

user202729

Oops too many tabs opened

but how can cv::FILLED undefined, it's right here in the docs...

Anush

if anyone has linux here, maybe they can help ?

user202729

Linux, but not Ubuntu.

Different package managers, different package names.

(I suppose)

But why...

askubuntu.com/questions/334158/installing-opencv -

What's your CV version?

(opencv)

ASCII-only

11:36 AM

@BoraCalim usually it isn't

just make

Anush

@user202729 I did sudo apt-get install libopencv-dev

user202729

@Anush Also next time if you post code/data/something you can Ctrl+K to format multiline code.

Anush

that's nice

user202729

stackoverflow.com/questions/2422514/… -

ASCII-only

@user202729 ctrl+a isn't needed

Anush

11:40 AM

@user202729 pkg-config --modversion opencv
2.4.9.1

I had no idea about that command!

user202729

opencv.org/releases.html

@Anush I have no idea too, but well... just google it.

Hm...

Looks like there are 2 (branch?), 2 and 3. (similar to Python?)

stackoverflow.com/questions/15340052/… -

answers.opencv.org/question/94624/… -

So looks like that you need version 3.1.

According to one of the link (far) above, the version installed by apt-get is 2.something.

xfloyd.net/blog/?p=987

Looks like you have to build opencv from source too.

docs.opencv.org/3.1.0/d7/d9f/tutorial_linux_install.html

@Anush Detailed instruction above.

Inpaint should just say that they requires at least cv 3. Users are not supposed to figure out that.

user202729

12:08 PM

(info: You can view the content of your own deleted messages)

ASCII-only

:O

@user202729 added explanation although there's a very high chance it's oncirrect

Leaky Nun

2

A: Find the 10-adic cube root of 3

Wolfram Language (Mathematica), 21 bytes PowerMod[3,1/3,10^#]& Try it online!

what sorcery is this

ASCII-only

@LeakyNun i just saw this lol

i was going to post "mfw there's a Mathematica builtin"

Bora Calim

guys

any of you moved from github?

ASCII-only

12:24 PM

@LeakyNun if you don't mind you might want to look over the explanation as well because there's a really high chance 1. people might not even be able to read it and/or 2. i made a mistake really early on (or at all) so it's invalid

HyperNeutrino

well just lost 50 rep because of OP failing to get their question right the first time they posted it ._.

@HyperNeutrino :|

@BoraCalim ngn did.

who is ngn

how do you add filler text for SE's 30-character limit thing

ASCII-only

12:27 PM

@BoraCalim the guy who made ngn/APL and ngn/k :P

@HyperNeutrino I try to pretend I didn't see that (i.e. add in random waffle)

(well, actually I never see the 30-char limit because every post with a link is >30 chars, and comments have 15-char minimum)

Adám

@BoraCalim codegolf.stackexchange.com/users/24908/ngn github.com/ngn

HyperNeutrino

okay

AdmBorkBork

@HyperNeutrino Did you set a bounty that disappeared or something? I'm confuzzled.

HyperNeutrino

@AdmBorkBork No, I deleted 3 newly invalidated answers with +2/-0 +2/-0 +1/-0

AdmBorkBork

Oh bummer

HyperNeutrino

12:37 PM

also I got an email to my outward correspondence email from a random person that found my SO profile :D

ASCII-only

@HyperNeutrino you... wait wat

HyperNeutrino

@ASCII-only some person emailed me asking how they should start off with CS/programming

ASCII-only

@HyperNeutrino weird. why you specifically :P

HyperNeutrino

No idea :P

It's not like I'm particularly active on SO or have any decently significant contributions

wait how do I have an SO gold badge?

oh right 10k question view badge

user202729

12:56 PM

@HyperNeutrino ???

HyperNeutrino

20 mins ago, by HyperNeutrino

@AdmBorkBork No, I deleted 3 newly invalidated answers with +2/-0 +2/-0 +1/-0

minus the "no"

user202729

Well and that's why some users don't like answer questions by 1rep users...

But...

Can you rollback?

HyperNeutrino

rollback what

user202729

@HyperNeutrino Add explanations.

HyperNeutrino

@user202729 no I was trying to edit my three posts into "don't edit" "questions after" "answers are posted"

user202729

1:00 PM

On Stack Overflow?

HyperNeutrino

no, PPCG

user202729

Which posts?

Then don't call they questions. Incorrect terminology :/

HyperNeutrino

my answers that I deleted

user202729

Of course I can't find it.

ASCII-only

@HyperNeutrino problem solved: "don't edit questions after answers are posted" <metalink1> <metalink2>

user202729

1:02 PM

Old answers, I suppose?

Use .

HyperNeutrino

they were from yesterday...

user202729

Well there are more activity on PPCG than I thought.

Definitely because me being inactive.

But... I don't really want to read and understand problem statements.

@ASCII-only FYI, SE has <sup> and <sub>.

Which can be used in <code> tag.

ASCII-only

@user202729 :| but code tag isn't nice

user202729

But the result is nicer...

ASCII-only

i guess it works though

*pre

user202729

1:12 PM

I made a minor edit.

I think it should be more correct but...

Er...

Both versions are wrong.

should be like this.

should be correct now.

ASCII-only

@user202729 am i not seeing it because grace period?

user202729

Yes.

ASCII-only

so this is final right

       x ≡ 7      (mod 10)
      x² ≡ 49     (mod 10)
         ≡ 9      (mod 10)
  x²×10ᵏ ≡ 9×10ᵏ  (mod 10ᵏ⁺¹)
3×x²×10ᵏ ≡ 27×10ᵏ (mod 10ᵏ⁺¹)
         ≡ 7×10ᵏ  (mod 10ᵏ⁺¹)

user202729

Yes.

user202729

1:38 PM

Does npm start use local ./node_modules/.bin?

ASCII-only

@user202729 probably?

user202729

(can somebody try it?)

good thing ASCII-only is not named somebody

Because (1) I don't have npm installed (2) I'm trying to run an app X from a package A.

I already installed A globally, but it has some dependencies.

Which is only installed locally.

Or at least I think so.

AdmBorkBork

Another plz-send-teh-codez question. Does it seem like we've been getting more of those lately, or just me?

user202729

@AdmBorkBork I think it's just you. Actually because we don't have stat.

Can't say anything for sure.

Zacharý

Is using inspect a bad thing?

user202729

1:44 PM

@Zacharý Inspect what? Browser?

Zacharý

@user202729 Python...

New Main Posts

-2

Q: How to get the lCM of 3 numbers in Python

Hi please answer my question. Answer it on python.

decision-problem python

user202729

@NewMainPosts Sometimes NMP is just very fast.

Never heard of it before.

Bora Calim

@NewMainPosts how can a person be this much unspecific and rude and ignorant at the same time?

user202729

@Zacharý I don't know.

Zacharý

1:46 PM

> Be Nice

user202729

Obviously the only way to have NMP's messages deleted after 2 minutes is to have a mod/RO involved, which is not a good idea.

ASCII-only

@user202729 anymore, you mean

Bora Calim

i think there should be something which alerts users with less than X reps that this is not SO when posting a question

Leaky Nun

This only prints the last 11 digits for n=12 and n=13. — Emigna 6 mins ago

this is interesting

ASCII-only

@user202729 if you npm i -g'd it then it works anywhere (i.e. deps are wherever they're supposed to be)

Leaky Nun

1:48 PM

this is because the 12th and 13th digits are 0

what should I do about this?

ASCII-only

well. crap

dzaima

@BoraCalim there are many things ppcg users would like to have so this place wouldn't be so flooded with off-topic stuff, but were stuck by SE's system

user202729

> applies to off-topic posts also

@BoraCalim Obviously SE doesn't care about us. But that's not the problem.

People just want to have their question posted.

Bora Calim

then why not post to SO

user202729

For me, just leave a close vote, a down vote and a delete vote.

Bora Calim

1:50 PM

i do not have down votes

user202729

With 5 such people the question will be deleted.

AdmBorkBork

@LeakyNun Is there a way to output as a string instead of as a number?

user202729

The good thing is, there are only very few questions here (per day) so they should be deleted very quickly.

Bora Calim

is there a thing which makes people flag at most 10 posts a day?

user202729

@BoraCalim Yes.

The more helpful flags you have, the larger the limit is.

Bora Calim

1:52 PM

i hope ppcg will not get big

user202729

Now I have 16.

Bora Calim

i dont want ot posts

user202729

> most blatantly OT questions are closed in under 5 minutes, and frequently deleted within the same day.

Bora Calim

btw, i have a nice hello world program in my language which is wip rn:

91+91+*c349**c349**6+c349**3+c99*6+c84*c349**3+c349**cd91+91+*1+c89*c++++++++++

nice huh?

i think it could be golfed much more but i will do so after finishing the language

user202729

@BoraCalim The only way to completely prevent off topic posts is to read every posts before they're posted on the main page.

The only thing prevents that is we don't build PPCG.

(btw: See PPCG v2 -- Axtell)

Bora Calim

1:57 PM

why not build another site for golfing then

user202729

Pyth ties Jelly? Guess I should golf my answer now

Bora Calim

guys

0

Q: Math Operations with Strings

Challenge Inspired in Alphabet Position Finder Given an string [a-zA-Z] and a mathematical operator [+, -] as an input, your task is to return the operation of each alphabet position from the string. Example Input: ["Hello World", "+"] => "Hello World" = [8 5 12 12 15 23 15 18 12 4] => sum al...

code-golf string number

what exactly does "-" do in this question

user202729

@BoraCalim Avoid onebox please

Which -?

For the one in [a-zA-Z] that's regex syntax.

Bora Calim

the subtraction symbol, like how is ["hello","-"] computed

user202729

Good question.

Zacharý

2:06 PM

Is taking 1 second for 1+2 bad?

Bora Calim

oh nevermind it just negates the value of the + thing

user202729

@Zacharý Very Bad.

people these days don't care about performance

Leaky Nun

Do we need to print leading zeros as well? Most answers (including my Java answer) are currently failing for those. i.e. n=12 outputting 87895134587 instead of 087895134587. Personally I would make it optional, since it would invalidate almost all answers.. — Kevin Cruijssen 12 mins ago

I don't know what to do

@AdmBorkBork I don't understand what you mean

Cows quack

you posted the cmc :D

Leaky Nun

@Zacharý well the asymptotic performance is what counts

user202729

2:09 PM

@LeakyNun "Everything are O(1)"

Poke

@user202729 what is the point of having the functionality if you're not going to use it

user202729

CMM: Should I edit old questions with new leaderboard, assume it doesn't bump too much?

@Poke I didn't implement it. If I did I would make the onebox take much less space.

Poke

@user202729 well don't shame others for using it

Cows quack

@user202729 s/are/is/ btw

AdmBorkBork

@LeakyNun I don't know enough Python or Java to know if it's onerous to output with leading zeros, or if it's even possible. Hence my question. If it is possible, and it's not too onerous, then I think leading zeros should be required since that's what the challenge is asking for.

Poke

2:11 PM

and get a bigger monitor

user202729

Jun 1 at 8:49, by ASCII-only

that is actually tiny

Leaky Nun

@AdmBorkBork is it too zerorous?

Poke

you don't find it ironic that you just oneboxed that?

user202729

...

Right...

Leaky Nun

that isn't irony

user202729

2:13 PM

Well chat message onebox is much larger than comment onebox, for some reasons.

Poke

it absolutely is

user202729

Anyway. Ignore it.

AdmBorkBork

@LeakyNun Har-de-ha-ha

user202729

About codegolf.stackexchange.com/questions/166400/… -

OP no longer improve the question, VTD?

Leaky Nun

say what

someone did it in 13 bytes with leading zeroes

user202729

2:16 PM

Can anyone explain why can't I just use a Ʋ? — user202729 3 hours ago

Leaky Nun

now I don't know if I should allow people not to print leading zeroes anymore

New Main Posts

0

Q: Math Operations with Strings

Challenge Inspired in Alphabet Position Finder Given an string [a-zA-Z] and a mathematical operator [+, -] as an input, your task is to return the operation of each alphabet position from the string. Example Input: ["Hello World", "+"] => "Hello World" = [8 5 12 12 15 23 15 18 12 4] => sum al...

code-golf string number

dzaima

@LeakyNun well that's because 05ab1e makes numbers == strings which is very helpful there

user202729

why 05ab1e has "take last digit" builtin...

Oh...

then it can't vectorize by default.

dzaima

@user202729 it's probably the "take last character" built-in

user202729

2:18 PM

For all languages there exists a challenge where it has advantage.

Also Jelly doesn't have for loops.

The closest Jelly have is ƒ. Currently at 17 bytes.

Bora Calim

how does jelly exist without loops

Cows quack

@ASCII-only nice answer and explanation, is there any particular reason why you use pypy?

user202729

@BoraCalim Corrected...

@Cowsquack Because it's on TIO.

Bora Calim

oh

user202729

Well TIO just have too many languages, you can choose any.

There is "repeat n times", "while" "repeat until loop" etc.

Cows quack

2:20 PM

I was wondering if pypy was faster, or something else

user202729

For such simple programs performance isn't very important.

Leaky Nun

20 secs ago, by user202729

5 mins ago, by user202729

Can anyone explain why can't I just use a Ʋ? — user202729 3 hours ago

Adám

@user202729 Isn't € a for loop?

user202729

@LeakyNun Uh...

@Adám ... probably.

Leaky Nun

@Adám no, it's applying the function to each argument in the input

user202729

2:23 PM

But it's not as "convenient" as other languages.

Zacharý

@Adám That's like saying ¨ is a for loop.

Adám

@LeakyNun In other words, it is running the function for each argument…

@Zacharý It is.

user202729

Leaky Nun

@user202729 isn't for loop just a sugar-coated while loop / repeat n times / fold over a range / applying function for each argument?

@Adám I see

user202729

Basically...

Leaky Nun

2:24 PM

but you have all of that

user202729

Because Jelly is tacit.

It can only handle 1 value at once.

(with exceptions)

With for-loop, the value has to be the iteration counter.

Leaky Nun

should it handle 1.5 values at once?

user202729

Then you can't really get any meaningful result out of the loop.

Adám

@Zacharý Compare :For i :In ⍳n ⋄ foo i ⋄ :EndFor with {foo ⍵}¨⍳n (or just foo¨⍳n)

user202729

@Adám But APL has variables. Jelly (almost) doesn't.

Leaky Nun

2:26 PM

the ⍳n looks like chet-vav

Adám

@LeakyNun Heh, it does a bit: חו

Leaky Nun

does it mean anything?

@user202729 almost

@LeakyNun No.

NMP is at +3/-3.

2:28 PM

Which is faster: set(map(lambda x: x.type, S)), or set(x.type for x in S)?

Leaky Nun

@Zacharý time it yourself

user202729

@Zacharý time it yourself

Adám

@user202729 Wait, you edited your message so that it became ninja'd?

user202729

Intentional.

Mr. Xcoder

2:41 PM

@user202729 re: My downvote is because the requirement to handle non-alphabetical characters is just fluff and I think that the specification is extremely unclear. If there were no examples, I wouldn't be able to understand the task. And our meta policy says that all challenges should be clear on their own without test cases/examples.

user202729

There are 5 VTC, so the DV are understandable.

Probably.

At least there are comments explaining what is unclear.

Dennis

4:48 PM

@user202729 Did you overlook/forget about this?

flawr

@Riker nice :)

(sorry, I'm too tired to come up with a pun)

caird coinheringaahing

Yeah, a pun would be too convoluted

flawr

And I thought I am the one who makes the bad puns =P

caird coinheringaahing

Nah, Zachary is the king of bad puns :P

New Main Posts

0

Q: Golf A Parentheses Matching Algorithm

You will be given a string s. It is guaranteed that the string has equal and at least one [s and ]s. It is also guaranteed that the brackets are balanced. The string can also have other characters. The objective is to output/return a list of tuples or a list of lists containing indices of each [...

code-golf string balanced-string

Bora Calim

4:58 PM

hey this is my question :))

New Sandboxed Posts

0

A: Sandbox for Proposed Challenges

I forgot towel day As you may know, may 25 is well known as Towel Day, because of the many uses a towel can have. A simple extract if the book "The Hitchhiker's Guide to the Galaxy" (personally i took this book as an "everyday guide") states: "A towel is about the most massively useful thi...

user202729

5:09 PM

... Right, I upvoted the comment but somehow forgot to implement it.

dzaima

5:53 PM

..this is why you do unit tests

Mr. Xcoder

@dzaima ಠ_____ಠ

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Q: Floating Point Input

In this challenge: rounding numbers. Most answers use floating point numbers, which means that many potential input values are impossible due to the limited precision. For example, the inputs .02675 and 4. In this challenge, that would mean rounding .02675 to 4 decimal places, which should resu...

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