@EriktheOutgolfer just an idea i had.

generally how *-Flak things go

like ill get a ping from Dj saying "I have a pain-flak like idea" and I will read and cry as I die inside a little

how long should I wait before posting a fastest code version of codegolf.stackexchange.com/questions/156988/… ?

@DJMcMayhem thanks

to avoid people shouting at me :)

@Lembik i wouldn't do it at all imo

it would prolly be marked as a dupe

but ask meta and see what they think

@Christopher oh! That would be a shame

I will ask on meta

Good idea

why would a fastest code be a duplicate?

we determine duplicates by their answers, not the questions

@Lembik well, I'd say sandbox it and we'll see

and I'm quite positive that none of those answers are competitive in fastest code

@Christopher a fastest-code version of this would be a substantially different challenge, and in my opinion more fun than the original

yeah, I think sandbox is a great idea, but I don't think this really needs to be meta-ed

I think the meta is a good idea

@ngn mine too!

I mean mean in my opinion too

that one is a duplicate

:)

I can delete it.. but the answer seems clear

that it's OK

you can leave it...it'll get closed as a duplicate, and allow for better searchability to find the original

I just want something to point to when people complain

which they always do :)

don't remove it

ok.. not removed

dupes are not a bad thing on meta. it just increases searchability

but you can dupe hammer it

but I will pose a fastest-code version tonight

which means in the next few hours currently

But take for example two identical challenges, where one is code-golf and one is fastest-code. Competitive code golf answers are likely to be brute force solutions, or written in things like GolfScript, which are notoriously slow....

thank you Martin Ender!

I wonder if he was thinking of me

ah.. I need to come up with interesting and larger test cases for the fastest-code version

hmmm

ok might take me a little longer

you know...we've got an unwritten rule somewhere: We say that challenges are language-specific, and that you are really only competing against answers in that same language...

but that's not always true

any ideas how to come up with test matrices for this problem?

we really only do it that way if the source code is involved in the scoring

@Lembik random

@ngn but which random?

also won't they then have to write code that can read in a matrix too?

the second point is the more important one

I am not sure there is any way round that sadly

@Lembik I'm not sure what you mean, wouldn't they have to anyway? maybe I should wait for the sandbox

@ngn The question will have to say I will run their code I think using test matrices

so their code will have to be able to read in any test matrices I come up with

@Lembik yes...

oh the sandbox link has gone codegolf.stackexchange.com

@Lembik Weird... It's still featured

@Lembik It shouldn't matter which matrices you use, if the code is written to take an n×n matrix.

@J.Sallé right but they still have to all run the same test matrices of growing size

As long as you use n×n matrices to test the codes, obviously

@DJMcMayhem thanks

here is my first attempt codegolf.meta.stackexchange.com/questions/2140/…

any improvements gratefully received

@Mr.Xcoder are you still about? there is a question about your reference implementation

Hey, I’ll take a look when I have time.

@ngn Are you referring to range(1, n*2+1) ?

@Mr.Xcoder cool

I suspect it's because mathematicians like 1-based indexes.

@Lembik yes

@Mr.Xcoder why do you do range(1, n*2+1) and not range(n*2) ?

@ngn I am asking the author :)

@Lembik btw, my comment should have been addressed to @Mr.Xcoder too, but tab completion didn't work...

aha.. we have the answer :)

thanks @Mr.Xcoder

CMC complexity-golf Given the prime factorization of n, return the prime factorization of n + 1.

If you can find a better solution the simple primeFactors . succ . product approach, that would be a major step towards the Collatz conjecture.

@recursive I am no mathematician :)

@Lembik The pleasure is on my side

@Mr.Xcoder Me neither.

@ngn do you think my sandboxed question is OK as is?

@Neil APL (Dyalog Unicode), 9 bytes ⊢⊃⍨|⍳⌈/∘|

@Lembik just a moment, I haven't read it yet, I'm still not sure the ref impl is correct

@ngn ah ok!

thanks so much for checking

@DJMcMayhem No, it is invalid

@Mr.Xcoder a bug? sigma[2*j-1] looks wrong when j = 0

@H.PWiz Wow. I even read the challenge earlier today, and I didn't notice that it was restricted source

@Mr.Xcoder you changed: for j in range(1, n+1): prod *= matrix[sigma[2*j-2]-1][sigma[2*j-1]-1] to for j in range(n): prod *= matrix[sigma[2*j-1]][sigma[2*j]] but the j is multiplied by 2, so now it's still off by 1 with the opposite sign

@Lembik: I just posted a comment to that effect.

@recursive I was copying you

but making it a little more specific

@ngn @recursive @Lembik Please edit in yourseves to address the bug. I have some stuff to do now :)

however you slice it we don't want sigma[-1]

fixed now?

looks good

cool

fixed the sandbox version too

@Mr.Xcoder sure, sorry for nitpicking on your otherwise working code

@Lembik I must be getting annoying already... Shouldn't matrix[sigma[2*j+1]][sigma[2*j]] actually be matrix[sigma[2*j]][sigma[2*j+1]]?

@DJMcMayhem I'm quite surprised as to the number of people who have misread the rules

@Lembik it probably doesn't make a difference because of the symmetry of the (no pun intended) symmetry group

csi is the best thing ever. I can use C# as a scripting langage without needing to define a class and Main method, there's a bunch of implicit imports for common functions, and it allows a #! line.

Python, I'm leaving you.

@Pavel java had the "beanshell" long ago :)

@ngn That's not the same thing. Beanshell is crap, I've used it before becoming englightened by the .NET way.

It's like if you took Java and gimped the already lacking standard library

csi is actually an official tool that comes with roslyn

@Pavel does it allow you to investigate crime scenes? ⍨

drum roll

@ngn Ah, I wasn’t annoyed at all. I didn’t want it to sound that way, sorry. I was just a but busy so I didn’t phrase that too well :)

does PDFLaTeX like not support mathbb or something like that ಠ_ಠ

How long should I leave my sandbox post until I make it into a challenge?

@JungHwanMin there's not a set time, but the usual consensus is at least a week.

From 2 days to 1 week, depending on how much feedback you received

alrighty

@J.Sallé well, the "official" recommendation is 72 hours

@EriktheOutgolfer really? I've never seen a meta post about that, I just said what I was told when I first joined here

yeah, I don't follow that recommendation either, I don't think I've ever left a challenge on the sandbox for less than 4-5 days or something

@Neil APL (Dyalog Unicode), 7 bytes: ⊃∘⍒∘|⊃⊢

@HyperNeutrino \usepackage{amsfonts}?

hm ok i'll try that

@ngn its not annoying it's really great. I am not at my computer for about 12 hours now. Please fix anything that is wrong

@Lembik done (at least the +1 / -1 wrongness)

@Adám wow that's complicated, I can tell there's a probability you've had a rough day, and this is the reason why

oh my god amsfonts "wasn't working" because I forgot the s at the end ಠ_ಠ

that's one of my most common errors...

in any language

but mostly when getting images from websites... .-. they can never be constant...

What is the Stack Exchange keyboard shortcut for cite? (applicable to places like Math.SE)

well, press ? and find out :P

not there :P I tried that already

then I guess there is no shortcut?

apparently not then ¯\_(ツ)_/¯

maybe you could ask somebody over their chat room, they might know better than me

@Mr.Xcoder no

...a tad late for a CMC, no? :P

CMC: Given the Fenwick tree representing the array a of positive integers in its flat representation and and integer n, return the sum of the first n elements in a.

VTC as off-topic, multi-part challenge

uh no it isn't (?)

1) parse Fenwick tree 2) take first n elements 3) sum

Parsing the Fenwick tree is literally just reading in a list

"convert them to integers"? no, that's not always necessary

ok but my point is that my CMC isn't really multipart :P it's just read a list and then do something with it

still multipart

What's a Fenwick tree

ok fine but there are a lot of challenges that take a list and an index...

@HyperNeutrino test cases please.

ok will do

@EriktheOutgolfer i relaized that after typing, i'm running at 50% efficiency right now

:/

unfortunately.

@Pavel efficient way of representing prefix sums of an array wiki

Uh, multi-part challenges aren't off-topic here ... ?

@ThomasWard not that I'm at 100% efficiency, currently watching Survivor Greece 2018 :P

@AdmBorkBork lol i hope that's the case

otherwise we'd just be implementing opcodes

@EriktheOutgolfer i'm literally at 50% efficiency because Err: Dead Tired

oh wow you should literally go to sleep

@ThomasWard that's the most common error in a programmer's life now isn't it?

get some of that 5 hour energy

;);)

programmers don't need sleep

@Poke why sleep when you can coffee

caffeine and vitamins are all you need

Chug five 5-hour energy drinks to get 25 continuous hours of energy.

while still too young for coffee, I've already decided against it

am I weird?

"too young for coffee"

lol I forgot doing ^ mentioned the latest message

[9, 8, 2, 0, 8], 3 -> 0
[0, 7, 0, 8, 8, 7], 3 -> 8
[7, 7, 7, 4, 0, 3, 0, 4, 4], 2 -> 14
[0, 8, 0, 5, 4, 7], 1 -> 8
[2, 2, 0, 0, 8, 1, 1], 6 -> 2
[7, 4, 6, 1, 2, 9, 0], 3 -> 1
[7, 8, 0, 8, 1, 2, 8, 0, 1, 8], 0 -> 7
[7, 6, 1, 1, 2, 8, 8, 0], 3 -> 1
[3, 4, 0, 7, 3, 5, 9, 4, 6, 6], 2 -> 4
[9, 9, 5, 3, 9, 1, 6, 6, 2], 5 -> 4

CMC: Given a list of integers, add 1 to all positive odd members and subtract 1 from all the negative odd members.

@EriktheOutgolfer the efficiency hit and its corresponding error of being dead tired is because of Err: Adaptation to Medication Required for a new med I'm on

@EriktheOutgolfer If so, I'll be weird with you. :D

@EriktheOutgolfer Say what? I don’t see how that is multipart

@Pavel jelly, 4 bytes: ḂaṠ+

lol you beat me to it (I had Ḃ×Ṡ+)

PS - 5-hour energy drinks taste nasty

I keep off of such drinks

Good ol' water.

good ol' sleep

@AdmBorkBork buddy of mine once said they tasted like horse piss. No idea how he knew what horse piss tasted like, but anyhow...

also my instinct says that when you drink coffee you're doing more harm than good, since you are still tired, but just have temporary 5-hour energy or something

I just drink coffee because I really like how it tastes. I honestly don't notice the caffeine affect

@HyperNeutrino could you enlighten me as to why the first 3 elements of that array sum to 0 instead of 19?

unfortunately it's also the taste that I have, I've tried to sip a little, 'twas godawful, spat it out

Supposedly, eventually your body adjusts to the caffeine levels, so that you need coffee just to reach what would have been your normal energy level.

I mean drinking coffee in the morning to wake up is sometimes necessary in place of sleep because unfortunately not everyone is able to get up as late as they'd like because work :P

isn't there legislation about that? and of course you should manage sleep properly :P (says who?)

@J.Sallé it's a flattened fenwick tree

@EriktheOutgolfer I remember thinking that too lol

Oh that's embarrassing, I forgot to convert the random arrays to Fenwick trees :P

[1, 6, 7, 18, 0, 4, 1, 32], 5 -> 22
[1, 8, 4, 13, 3, 8, 6, 27, 4, 4], 8 -> 31
[9, 12, 5, 25, 9, 12, 0, 37, 2], 4 -> 34
[5, 11, 1, 17, 7, 7, 5, 29, 8, 11], 7 -> 29
[6, 12, 8, 25, 6, 11, 1, 42, 6, 9], 5 -> 36
[6, 11, 5, 25, 5, 13], 2 -> 16
[6, 11, 8, 23, 4, 5], 2 -> 19
[9, 18, 5, 28, 0, 2, 2], 4 -> 28
[1, 5, 4, 10, 2, 10, 0], 4 -> 12
[0, 3, 3, 9, 9, 10], 0 -> 0

that should be actually correct ಠ_ಠ :P

anyway brb o/

@ngn I've no idea how that sum works. The gif doesn't help >.>

@J.Sallé idk either, i'm reading about it :)

@Pavel Appleseed, 47 bytes: (partial map(macro(n)(+(*(sgn n)(mod n 2))n))?)

@DLosc Is partial something that got added recently? I don't recall seing it before.

Not terribly recently, let me look...

No, it was there in the original commit.

Huh

Also, 46 bytes: (partial map(macro(n)(+(*(sgn n)(odd? n))n))?)

@Pavel Proton, no lambdas, 52 bytes: map(((((%)&2),((*)&1,abs+((or)&1))+*(/))+*(*))>>(+))

@HyperNeutrino How did you manage to have more parentheses than the Lisp solution

Proton, lambda, 30 bytes: a=>[e+(e%2)*(e>0?1:-1)for e:a]

Also, is & the partial application operator?

@Pavel ¯\_(ツ)_/¯ operator precedence is annoying for function compositions

@Pavel yes

@HyperNeutrino Is that Proton's version of point-free?

@cairdcoinheringaahing basically yes :P

What would happen if I did map((((%)&2, ... instead?

actually that would work

i'm bad

well it should be while (i > 0)

wait it doesn't make a difference

yeah I think that's right

@HyperNeutrino same thing

@HyperNeutrino so if for example i=4 (that is, n=4), the result should be only the fourth (at index [3]) element?

yeah

@HyperNeutrino but not in others with n=4

huh that's weird. no idea why, sorry

I'll have to look at my implementation again but busy rn

anyway gtg o/

@HyperNeutrino no prob, thanks to your cmc I feel like I learned something interesting today - Fenwick trees :)

Q: How long should a challenge writer wait before declaring winners in a CnR challenge?

ಠ_ಠ SE chat isn't letting me edit that

@cairdcoinheringaahing forever

no need to declare winners IMO

codegolf.meta.stackexchange.com/questions/2140/… any last foodback?

@WheatWizard for the badges

> foodback :/

@Christopher badges?

@WheatWizard ones involving accepted answers

@Christopher it's been downvoted, so I'd advise against posting it in its current form

@Christopher That's not a really good reason.

@EriktheOutgolfer it was downvoted before it's current form

@WheatWizard +15?

@Christopher True, but I don't think 'the current form' addresses every problem raised

@DJMcMayhem like what?

i have been trying to find what is wrong :P

@DJMcMayhem I did address that iirc test cases for the winning will be posted 1-2 weeks after the challenge is posed

I missed that

the 2nd one idk how to fix

i do want actual functioning answers :P

But somehow, that makes it less clear. winning and score are not the same thing?

one sec

@Christopher Specify a machine

Simple fix

@DJMcMayhem i wanted to say TIO but then you have to use TIO :/

Also, TIO limits you to 1 minute, so that would be super hard to test :P

yeah

WW had a good point about using integers instead of strings

the mod use :P what does this mean

@DJMcMayhem yeah i mean yeah

lol mods are users too

@Christopher ...oO(The same thing as literally every user means?)

@DJMcMayhem crap he is on to me

oh wait

@DJMcMayhem Dennis, somebody stole another trademark ;P

did WW mean that you take integer input?

@EriktheOutgolfer * ...oO(flags for plagiarism needed?)*

No, he was saying that the output should be an array of ints rather than a string

oh

isn't that the same thing?

just without the -A flag

No. It allows negatives

huh that works

And also, because it's the same thing, there's no reason to treat it as strings

yeah

i still would like to take text input though :/

have answers support both?

oohhhh

perhaps that can be a super sick CnR

I have no clue what you mean

one sec

@mods do you have the stupid message delay?

@Christopher So 'support both' means 'do it with ints', but then add a confusing after note about how there might be a flag added which doesn't actually affect what your program does

@DJMcMayhem no, support taking text and int input (not at the same time :P)

what about you have ur code. and you give a levithan distance, the robbers have to find the code with that levithan distance that takes text input instead of integer

But why? What advantage could that possibly add?

hmm more changes needed

@DJMcMayhem just idea floating in the head

i really want to make a CnR because I mostly work on Code-Golf questions

@DJMcMayhem you think that i could viably make this into a fun CnR?

@DJMcMayhem me and you have sent the same amount of messages this week :P

@Christopher No offense, but not really.

@DJMcMayhem thanks, makes sense

@cairdcoinheringaahing just follow what the original plq did

@totallyhuman Its about 9 days too late for that :P I think a month is a reasonable time to accept a winning cop and robber

@cairdcoinheringaahing how will you accept a robber?

nah the winning criterion for robbers is the most answers

so which answer will be accepted?

Anyone know how you would find the path of an image (from a lens or something) of a moving particle?

high hopes for science in tnb :P

:p

I might have misspoke.

I meant to say given a moving point light source and a fixed mirror, how would one go about finding the areas that are not illuminated at any point in time?

I got my optics words mixed up before

@Zacharý find the path of the light source and reflect it across the normals of the ends of the mirror or something?

I think I got it. Parametrize the path. Find formulas for the angle between a point on the path, an endpoint, and the mirror itself. Then find the minimum/maximum (depending on how it's measured) angle across the path using derivatives. Since either larger or smaller angles (depending on measurement) determine the amount of shadow, that should work. (I suck at explaining things)

@Zacharý is the mirror flat

Yes.

@Zacharý Then you don't need a derivative to find min/max angle at all right

just use the angles from the two ends of the mirror