The Nineteenth Byte

New Sandboxed Posts

00:24

0

Who ordered chicken? Chicken is what poor people eat You are a chef in the luxury hospitality industry. You decide to serve chicken breast to your guests for lunch. When served the guests pick through their meal and the primary guest states to their company Who ordered chicken? Chicken is ...

New Main Posts

00:43

0

Q: Convert to Suzhou numerals

Suzhou numerals (蘇州碼子; also 花碼) are Chinese decimal numerals: 0 〇 1 〡一 2 〢二 3 〣三 4 〤 5 〥 6 〦 7 〧 8 〨 9 〩 They pretty much work like Arabic numerals, except that when there are consecutive digits belonging to the set {1, 2, 3}, the digits alternate between vertical stroke notation {〡,〢,〣} an...

ASCII-only

01:09

after 50 billion iterations

:|

wait

there are people that got part 2 in 9 minutes?

quartata

@NewSandboxedPosts what is this challenge

Dennis

@NewSandboxedPosts I did. It was delicious.

ASCII-only

...oh

part 2 is surprisingly easy

with human assistance

also why is it that i always mess up

if not an off-by-one error it's an off-by-one-order-of-magnitude error

Shieru Asakoto

01:33

just let me ask a dumb question

but will I be vulnerable if I enter my, say, password, into a page with some mixed image content that loaded as the background through css

Downgoat

Question: what is the windows C build process like? Does it also go Backend -> Object File -> Linker -> Executable?

Because I can't figure out what windows' linker executable is

Anonymous

01:49

@Downgoat Depends on the compiler. Using GCC, everything is normal. Using MSVC, everything is done in one go from the user perspective, but usually it fails due to lack of full C99 support and basic C11 support.

quartata

@ShieruAsakoto just the image was over http?

or the CSS?

if the CSS was loaded over http, youre vulnerable because you can inject JS through that

Shieru Asakoto

the css is over https but that line of code is like url(http://.....)

quartata

i think you can embed JS in an SVG also?

so if that got sent as the image

Shieru Asakoto

or more specifically it was something like url(http://a.website.com/the_picture.jpg)

quartata

yeah so youd be vulnerable if that got MITM'd

it could replace the JPG with a malicious SVG

i think those can be loaded as css background images right

obviously they work in img tags

Downgoat

02:04

@Mego Windows has GCC? O_o TIL

does it have ld or does GCC have its own things to do that on windows

right now VSL uses ld command to do linking because portability issues with clang

Anonymous

@Downgoat Through mingw, yeah

Downgoat

can anyone with windows who has ld tell me if there is a -arch flag available?

Shieru Asakoto

is it something like this?
<script type="text/javascript"><![CDATA[
console.log("pwned");
]]></script>

within an svg

quartata

24

Q: Including JavaScript in SVG

I am trying to create an interactive SVG code with JavaScript, by embedding the JavaScript in the SVG. I don't know if this is the right way to do this: <?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/s...

javascript svg interactive

yeah looks like it

Shieru Asakoto

but when I tested on localhost nothing happened

quartata

02:11

I think you need the DTD

Shieru Asakoto

<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd"> this?

Downgoat

@quartata JS in SVGs isn't run

quartata

@Downgoat hm?

Shieru Asakoto

oh there was no the first xml line lmao

quartata

are you sure? im seeing some stuff on security SE about this as an injection

Downgoat

02:13

@quartata if they are loaded as an <img> or something they won't be run only if directly embedded

Shieru Asakoto

`<?xml version="1.0" encoding="utf-8" standalone="no" ?>`
`<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">`
`<svg version="1.1" xmlns="http://www.w3.org/2000/svg" onload="pwn()">`
`<script type="text/javascript">function pwn(){console.log("pwned");}</script>`
`</svg>`

Downgoat

@quartata if that was true I can host an SVG to send me all your session keys and post it in TNB

Shieru Asakoto

my test pic is now this

Downgoat

@quartata this is pretty much only old IE though IIRC

Shieru Asakoto

@Downgoat how about an SVG loaded by CSS?

Downgoat

02:15

@ShieruAsakoto yeah that still won't run JS

security issue with mixed content is mainly tracking and MITM/phishing

quartata

w3.org/wiki/SVG_Security

says it has to be loaded as an embed?

so i guess as an img tag its safe

Shieru Asakoto

> For this reason both, SVG image and SVG resource must be fetched with the same policies. The one with more restrictions preferred. Therefore, SVG resources have the same restrictions as SVG images.

this line?

quartata

>Scripts must not be executed

under the other thing

Shieru Asakoto

bc Google and Mozilla said that url(blahblahblah) within CSS is considered mixed active content

quartata

@Downgoat to be fair ive demonstrated that oneboxing is not particularly safe but youre right it requires active user interaction

Shieru Asakoto

02:20

but they just don't block that as per W3C specs

> Requests whose initiator is the empty string, and whose destination is "image".

> Mixed content is optionally-blockable when the risk of allowing its usage as mixed content is outweighed by the risk of breaking significant portions of the web.

so anyway, I may only be vulnerable to being read the cookies but not my passwords entered after that page is loaded in this particular case?

quartata

the primary thing is knowing who loads a given page

Shieru Asakoto

since other UI images and connections are over HTTPS

quartata

https normally would hide what page someone is requesting

but if you know your resource is on a given page then you can track

since its another origin reading cookies is not the issue

Shieru Asakoto

Welp the page doesn't refresh even if the content is entered tho

because it used sth like XMLHttpRequest (ofc over HTTPS)

I think those image resources loaded from a secure CSS can't modify other elements not specified can they

Shieru Asakoto

02:58

anyway thanks for the answers I was just nervous about possible code injection only

New Main Posts

03:46

-1

Q: Find the size of string which is good and has the least importance

Define a good substring as a substring which begins with 'x', ends with 'z' and has a length divisible by 3. Define the importance of a string as the number of good substrings it intersects with (excluding itself, if it is itself good). Consider a string of length N (1≤N≤10^5) which is compose...

algorithm

mbomb007

04:36

@Dennis K. Then Martin's documentation is wrong.

The Unary Arithmetic guide has programs that don't work in 1.0

Dennis

Yes, it says so at the top.

> Under construction... (...and out of date. This was written for Retina 0.8.2.)

Shieru Asakoto

Oh some additional information

The entry page is opened as an iframe after pressing an icon on the page

when the background is loaded the iframe does not exist yet

Οurous

04:51

The thing you're worried about goes in the iframe or in the background?

Shieru Asakoto

the password entry is in the iframe

and I have checked the css that the problematic lines are just background-image:url(http://blah.blah/blah.jpg)

and the browser shows the https:// with an info icon

Οurous

If anything, the fact that it's in an iframe makes it more secure because you also have Same-Origin-Policy protections between the page and the iframe.

At least from the perspective of a stylesheet in the parent page.

Disclaimer: I don't do web-dev or front-end anything, so don't take my word on this

Shieru Asakoto

so as long as the iframe is opened with HTTPS without mixed content I'm safe with that?

But those css lines can't load something that alters that icon can they?

Οurous

Yeah you'd be safe. You mean the browser this-is-secure icon?

Shieru Asakoto

> Yeah you'd be safe. You mean the browser this-is-secure icon?

*and the browser shows the https:// with an info icon*, so yes

and the pressing an icon to open iframe one is in the page content

Οurous

05:00

In theory, it could change the icon. However assuming you're using a current and sane browser it would be due to a bug in the browser (one that is unlikely to be present, and would be fixed post-haste if found). So not in practice.

feersum

lost chocolate chips in my printer again

2

At this point I'm surprise it doesn't ooze on hot days.

Anonymous

@feersum How does that happen once, much less multiple times?

feersum

Bag of chocolate chips sitting on the printer

Top-loading document feeder

They fall out of the bag and into the document feeder.

Shieru Asakoto

thanks, so as long as there is no method for loading and executing malicious code through a static JPG url()I'm still safe as long as not interacting with those elements right?

Anonymous

@feersum I see a near-effortless way to prevent this issue :P

feersum

05:06

Masking tape?

Anonymous

Moving the bag away from the printer

ais523

CMC: given a list of pairs (in some appropriate format), output each first element of a pair followed by each of the second elements it pairs with (e.g. [[1,3],[2,5],[1,4]] could output [[1,[3,4]],[2,[5]]]

I just tried to solve this in Jelly for something offsite, it seems surprisingly difficult there, and yet it's pretty easy in most practical languages, which struck me as an unusual combination

(unfortunately, "easy" does not mean "terse")

Οurous

@ShieruAsakoto yep.

New Main Posts

-1

Q: Find index of heaviest ball

Mark has N balls, numbered 1 through N. No two balls weigh the same. You want to find the heaviest ball but you do not know which one it is and Mark does not want to just give it to you. Therefore, he decided to play a game with you. You may ask Mark at most Q=4+N/2 questions. In each question, ...

code-golf code-challenge programming-puzzle

Shieru Asakoto

05:23

I had a 74B JS answer for that only

Shieru Asakoto

05:58

It turned out that the resource was automatically reloaded using HTTPS (with a status code of 301 in between). Solved

lirtosiast

@Dennis Hmm, that's too bad. What about on meta, as "what features make golfing languages golfy" or a separate question "what features make golfing languages fun to golf in"?

FrownyFrog

@ais523

tio.run/##y0rNyan8/z/w6J7DG44seLi7@////…

ais523

@FrownyFrog hmm, that'd be, what, 8 bytes if you took input as a list of pairs rather than two lists in separate arguments?

FrownyFrog

don’t know this language

ais523

Jelly's probably the most popular golfing language on PPCG, which means that on questions it's suited for, it normally ends up winning

this CMC's a little tricky in Jelly because it's hard to get all the values into the right places

FrownyFrog

06:08

I mean I’m not good at it

ais523

fair enough

FrownyFrog

how would you do it with a list of pairs?

ais523

with your approach, you could do something like using Z to transform it into a pair of lists, then use / to reduce your code over that pair

FrownyFrog

yeah that part I get

ais523

you'd also need a grouping character (I think it might be doable with one grouping character with a bit of rearrangement?) to make the / apply to the entirety of your code

FrownyFrog

06:17

I mean the syntax

ais523

here's the obvious way: Try it online!

FrownyFrog

thanks

ais523

but that uses two extra characters

I can't see an obvious way to do it with one but suspect it's possible somehow

Shieru Asakoto

07:36

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/BigInt
Finally Mozilla documentations have BigInt

ASCII-only

finally

wow, doorknob was first to both stars for day 13

wonder if we should do aoc for past years

Jo King

@ASCII-only He was second for the first star

anonymous user #193354 was first

Shieru Asakoto

07:59

Last updated by: coolaj86, Dec 12, 2018, 1:23:06 PM
about one day ago

Jo King

08:21

Any idea how to talk to a user with a chat suspension...? The Sandbox question is at 20 comments and counting

Shieru Asakoto

Which question?

Jo King

@ShieruAsakoto here

Shieru Asakoto

> Who ordered chicken? Chicken is what poor people eat.

Sorry but that made me laugh

btw the discussion seems to be growing to some hate

Jo King

08:47

@ShieruAsakoto Yeah, that's probably why they got suspended from chat in the first place... They really likes either misinterpreting common phrases or insisting that the phrases are meaningless and don't apply to them.

ASCII-only

09:04

@JoKing and second on second star :P

Jo King

so it cancels out?

ASCII-only

yeah

random thought: I'd imagine you should be able to get sub-5 minutes for every single second star with a language that's good enough

oh yeah. i also cheated with Julia for most of the numbers so i'm now like 10th overall in code-golf.io

I kinda feel bad

Fatalize

"i also cheated with Julia" ( ͡° ͜ʖ ͡°)

ASCII-only

:|

i walked straight into that one didn't i

Jo King

well, just completing all the holes will get you pretty high

*on the leaderboard

ASCII-only

09:08

not if you use ~~java~~ lisp

10 points per hole :P

Jo King

Wait, people use Lisp?

ASCII-only

@JoKing primo uses basically everything

i could do 2 more challenges in lisp and that would put me at the top

hmmm

Jo King

His profile page is insane

all those firsts

betseg

10:46

im trying to do today's aoc's part 2

my program works with the sample input

but not the actual input

what

betseg

11:14

ok nvm solved it

dzaima

@betseg are you by saying that implying that that's the first time that's happened to you? :p

New Sandboxed Posts

11:40

0

A: Sandbox for Proposed Challenges

Output a number \$n\$ such that: \$n\text{mod}10=5\$ \$n^2\text{mod}10^{10000}=n\$ Shortest code win. Sandbox mainly to check duplication

betseg

@dzaima well in AOC yes :p

but considering its my 13th aoc puzzle

the problem was that i was sorting by y,x not x,y

dzaima

11:53

@betseg lucky you :p

Dennis

12:32

@lirtosiast I don't think that would be on topic. Meta is for questions and discussions about PPCG, and a way to communicate with Stack Exchange.

New Sandboxed Posts

13:12

0

A: Sandbox for Proposed Challenges

Non-overlapping Matrix Sum Given k m by n matrices, output the maximum sum possible using one element from each matrix such that no two elements are from the same position. It is guaranteed that k<=mn. Ex. 1 2 1 2 3 4, 3 4 ->7(3+4, can’t choose the 2 fours in the same place) Is the challen...

HyperNeutrino

14:18

@betseg ok I've made 7 solutions to AOC 7.2 that all work with the sample input and all fail for the actual input and I currently have a 10 minute throttle on that problem and I've decided to just give up

primo

@ASCII-only that was my plan

In fact, i just finished: code-golf.io/scores/lisp

betseg

14:33

@HyperNeutrino wanna join PPCG leaderboard

Also, nice #93 spot on global leaderboard

HyperNeutrino

15:07

@betseg sure :D

also lol ty

i stayed up til midnight twice to solve it early to get that :P

betseg

15:41

@HyperNeutrino chat.stackexchange.com/transcript/240?m=47895631#47895631 .

Pavel

Does anyone have or knows where one could obtain a precompiled linux Perl 4 binary

betseg

It's more than 25 years old

Something compiled that long ago won't work with today's libraries

Pavel

Well hopefully someone has tried compiling it on modern hardware (and succeeded)

El'endia Starman

16:59

@Pavel Whatever do you need it for??

Pavel

@El'endiaStarman TIO, and I got one just now

El'endia Starman

Well, congrats! :P

Pavel

Hmm, hat research is going relatively slowly this year

I think we knew more about secret hat triggers at this time last year

Quintec

I know nothing and have 0 earned hats :P

Pavel

Quintec says, wearing a hat

Erik the Outgolfer

17:13

sees fresh new hat

betseg

did someone say

hats

Pavel

yes

AdmBorkBork

@Quintec And one unearned hat

Erik the Outgolfer

actually, Quintec has the two hats that you don't have to do anything to "earn" them... :P

AdmBorkBork

17:33

How do you see hats that others have earned?

J. Sallé

Hats are great.

Erik the Outgolfer

@AdmBorkBork click on profile picture on profile

if it doesn't work, they haven't earned anything

AdmBorkBork

Derp, thanks.

Quintec

18:13

That hat required the fact that I signed up on random sites a few months ago, lol, I don’t consider it earned

the other is viewing stack overflow teams

New Sandboxed Posts

0

A: Sandbox for Proposed Challenges

Standardize the Samples code-golfmathstatisticsarray-manipulationarithmetic Challenge Given a list of floating point numbers, standardize it. Details A list \$x_1,x_2,\ldots,x_n\$ is standardized if the mean of all values is 0, and the standard deviation is 1. One way to compute this is by ...

moonheart08

19:40

Anyone know if there's a good way to optimize this statement, or is it optimal?
https://github.com/ThePowderToy/The-Powder-Toy/blob/87fb94ce949615e6722f0f39076e87ecc5164a81/src/simulation/Simulation.cpp#L2773

lirtosiast

@moonheart08 Are you calling it a million times a second or something?

moonheart08

@lirtosiast more like 100000 times per second, but pretty much.

it's used by TPT for some important stuff in the core particle loop, so it runs once per particle.

s/once/a few times/

Well, i guess compilers are magic. Changing it to output a char like it should makes it's asm footprint smaller

DJMcMayhem

19:59

I'm not surprised

Also, what's with the return type declaration? unsigned Simulation::direction_to_map(float dx, float dy, int t)

Just unsigned by itself?

betseg

comparisons to zero, bitshifting and oring are some of the most basic operations so i dont expect it to be able to be more optimized

also is int t used in the function?

moonheart08

@DJMcMayhem it's old C code that was clumsily ported to C++. It's assuming implict int

@betseg It's not. Due for cleanup :P

TPT in general needs a lot of refactoring

Nathan Merrill

20:41

Factorio had a similar problem. They were moving millions of items each tick. They refactored it so groups of items are moved with a single operation. I don't know the internal workings of TPT, but some sort of dynamic grouping may help to make it faster

it makes your code more complicated, but if you're really going for efficiency, you are going to have complicated code

7

Skidsdev

Factorio is a real testament to good optimization

Οurous

@NathanMerrill A painful truth right there

DJMcMayhem

@Skidsdev And really really good devs.

Skidsdev

@DJMcMayhem agreed

DJMcMayhem

No microtransactions, single price set in stone, tooooons of free updates to a fairly old game and a lot of transparency.

Not to mention the almost 300 weeks of FFF without missing a single one

Anonymous

20:44

@DJMcMayhem Except for the one time they changed the price :P

DJMcMayhem

@Mego Well yes :P

New Sandboxed Posts

20:55

0

A: Sandbox for Proposed Challenges

Rotation invariant fingerprinting Tags: code-golf, array-manipulation, hashing, polyomino Related: Which tetromino is this? Imagine we have some polyomino and would like to uniquely identify them, however the polyominos can be rotated, so blindly hashing them won't give us the same fingerpri...

Veskah

21:05

The Friday Factorio Facts that discussed sales has a neat graph where basically massive price spike during the grace-period before the price-bump but before and after was relatively consistent

Friday Factorio Facts is just a good read in general. Many neato things

Skidsdev

Plot Twist: They only upped the price because they knew announcing they were going to do so would cause a spike in sales

Zacharý

It looks at first glance as if there has been a spike in activity.

Veskah

@Skidsdev Madre de dios...

Zacharý

@Veskah Spanish, right?

Veskah

Am i? No. Is that, yes

Zacharý

21:11

(I would never try to pin a language like Spanish on location, too widespread.)

Nathan Merrill

I speak American

AdmBorkBork

Darn right, pardner, and what a hootin'-tootin' language it is!

Οurous

I speak New Canastralian

Zacharý

o_O

Skidsdev

I speak english, but all of my colleagues speak canadian. Working would be so much easier if we all spoke the same language

Nathan Merrill

21:21

I heard that canadian is similar to english, because they are in the same royal dialect

AdmBorkBork

> remarkable for its suspicion of poets. link

Erik the Outgolfer

lol

Οurous

@AdmBorkBork That's. Uh. Fascinating.

I mean the combination of nationalities is correct at least with the exception of Britain.

Skidsdev

> Left-Leaning College State

"Political Freedom: Some" is perfectly in-line with the UK, and probably Australia, but Canada's actually pretty good with political freedom, I'd put it under "good" or "strong" (Definitely not "Superb" though) for canada

Quintec

23:14

Guys, I "earned" my first hat: earning a silver badge by posting "reeeeeeeeeeeeeeeeeeeeee" in chat

lirtosiast

I downvote that

Veskah

If you want that to work here, it better be a pretty sweet regex

Arnauld

Just wondering: is there an official terminology for what I've temporarily called corner-cells and side-cells (in this post) on a hexagon grid / spiral?

Οurous

23:33

@Arnauld "Order-1" and "Order-2" in respect to edges connected to the previous layer (subgraph?)

Luis Mendo

while versus do...while

4

Arnauld

@LuisMendo Excellent :D

@Οurous That sounds good. It might introduce some kind of confusion with the number of neighbors at the time the cell is added (which is a different thing). But I think I'll go with that anyway. Thanks!

DJMcMayhem

I'm evil... I have a friend that likes answering riddles, but isn't extremely mathematically or programming inclined. He always asks me for riddles (along the lines of Labrynth/knights and knaves, or Josephus problem). I just gave him The Goldbach Conjecture as a "riddle" 🤣

Veskah

@DJMcMayhem Isn't that how one of the Millennium problems got solved?

DJMcMayhem

Oh, idk.

lirtosiast

23:41

@Veskah only one Millennium problem has been solved (Poincare I think?)

DJMcMayhem

Coming up next week: The Collatz Conjecture, followed closely by Fermat's last theorem.

@lirtosiast Correct

Veskah

Maybe not one of them, but I know a one of the long lasting conjectures was accidentally solved as a homework assignment

lirtosiast

It is some pop culture thing that a professor gives an unsolved problem and someone solves it

Idk if it's true or whether it was long lasting

Veskah

Thought it was substantiated but let me reach into my bag of proof

Nope, only nil in there

Arnauld

@LuisMendo Did you mock it up yourself? (I can only find the original picture without the speech bubbles.)

Luis Mendo

23:44

@DJMcMayhem The fun will not last much if they know how to google it :-)

@Arnauld I saw it on Twitter

lirtosiast

@LuisMendo Googling math problems is a nontrivial skill

Luis Mendo

:-D

Arnauld

Ah ok. I guess I can just re-post it without any credits, then.

Veskah

@lirtosiast If you can trust snopes, snopes.com/fact-check/the-unsolvable-math-problem

Luis Mendo

@Arnauld Like I did :-D Here is the link

DJMcMayhem

23:48

@lirtosiast Truth

@LuisMendo of course I described it to him, I didn't give him the name

Luis Mendo

Aw, that's evil!

DJMcMayhem

@lirtosiast Good will hunting?

Or wait, I remember what you're talking about, it was some well known mathematician. But I don't remember who.

Veskah

Click the snopes link, t'was George Dantzig

Riker

CMC: do AoC day 13 in Mornington Crescent

El'endia Starman

Yup, George B Dantzig. IIRC his story was part or all of the inspiration for Will Hunting doing the same sort of randomly-solved-unsolved-math-problem thing in the movie.

Veskah

23:51

GWH tweaked it by having problems on a blackboard outside of the class and Matt Damon solved 'em while doing his janitorial rounds

Riker

also congrats @Doorknob for being first for d13 on aoc

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