The Nineteenth Byte

caird coinheringaahing

16:07

Does anyone here know regex?

ToxicFrog

@cairdcoinheringaahing ?

Wheat Wizard

o/

Cows quack

sorta

ToxicFrog

@cairdcoinheringaahing don't ask to ask, just ask

caird coinheringaahing

If I want to match a string so that it separates every character, except ones preceded by a question mark, how would I do that? e.g abc?efg => [a, b, c, ?e, f, g]

betseg

16:19

yay i posted my first answer in 15 days \o/

Doorknob

@cairdcoinheringaahing Find all matches of /\??./

Wheat Wizard

@cairdcoinheringaahing [?]?. will mach each case separately

regex does not do separations

It just matches things

caird coinheringaahing

@WheatWizard yeah I know, I have a function that separates things on matches, it was just the regex to get matches that I was looking for

@Doorknob what is the emoticon at the end of your PPCG profile? :wq?

Doorknob

Not an emoticon, a vim command. Combination of :w (write) and :q (quit).

musicman523

@cairdcoinheringaahing not an emote

ninja'd

caird coinheringaahing

16:24

@Doorknob ok, that makes sense. I was trying to figure out how that could be a face q:

Wheat Wizard

You can use :x, just saying

musicman523

@WheatWizard but don't accidentally use :X

Wheat Wizard

Good point

betseg

what does it do

musicman523

:x is the same as :wq

:X will encrypt your file

betseg

16:27

o no

Doorknob

@WheatWizard The point is that it's recognizable, not what I actually use. :P

@musicman523 Not quite. It won't write to the file if no changes have been made.

caird coinheringaahing

@Doorknob good. As a mod of code golf, all your code should be as golfy as possible :P

New Meta Posts

0

Q: On type restrictions

Recently I had an interesting interaction on one of my questions. A user posted this answer in C++. My question requires a function on the positive numbers that has some properties, the user's answer essentially implemented the function add 1, which does not satisfy these properties on the posi...

discussion

musicman523

@Doorknob Gotcha, I suppose this could make sense in some cases but I don't think it would usually matter (probably only if you open a brand new file in Vim or if like your hard drive dies or something)

betseg

codegolf.stackexchange.com/q/135193/56721 c golfier than python?

Cows quack

16:31

There was a moment when I thought n>=q would be golfier than n=n>q

betseg

lul

caird coinheringaahing

@HyperNeutrino I was reading through this when I noticed the comments below the question ಠ_ಠ

HyperNeutrino

@cairdcoinheringaahing hehe

caird coinheringaahing

@HyperNeutrino the other user though

HyperNeutrino

ikr

whoever it was even ಠ_ಠ

caird coinheringaahing

16:41

@HyperNeutrino long gone now i think.

HyperNeutrino

yup.

hey I can chain onto OEIS challenge now

Doorknob

@musicman523 Well, if you don't want make to recompile a file for no reason then it's useful, for example.

caird coinheringaahing

@HyperNeutrino have you got an answer?

HyperNeutrino

not yet

neither do I have a language to use >.<

MORE PARTITIONS

DJMcMayhem

@Doorknob my "emoticon" is better :P

caird coinheringaahing

16:41

@HyperNeutrino F#?

HyperNeutrino

hm

caird coinheringaahing

@DJMcMayhem checking I agree

@DJMcMayhem also, your profile picture is much better. Everyone likes cats!

HyperNeutrino

@DJMcMayhem The capitalization of "The [Aa]lgorithm" (hehe I detected it with regex) is inconsistent ಠ_ಠ

caird coinheringaahing

@HyperNeutrino it means that it can't be detected by regex

Doorknob

llama@llama:~$ cat > Makefile
a: test
	echo hello
llama@llama:~$ touch test
llama@llama:~$ make
echo hello
hello
llama@llama:~$ touch test
llama@llama:~$ make
echo hello
hello
llama@llama:~$ make --version | head -1
GNU Make 4.2.1

(@musicman523)

HyperNeutrino

16:44

@cairdcoinheringaahing no I mean the A is not capitalized consistently lol

musicman523

@Doorknob I just did the same thing, that's why I deleted :P

HyperNeutrino

@Doorknob again, WHY are you a llama??? :P

caird coinheringaahing

@HyperNeutrino its deliberate so that Jon Skeet can't find it back :P

DJMcMayhem

@HyperNeutrino /\cthe algorithm/ is golfier

Doorknob

@musicman523 Oh, didn't see that. :P

Luis Mendo

16:44

@DJMcMayhem Pity you couldn't work on the answer. It's currently leading :-) BTW are you planning on doing the change suggested here? Otherwise I may have to remove the link to that answer as the third example here

Step Hen

Yay me, I decided to break the mold and not do ... 5 - 3 - 1 - 2 - 4 ... for the infinite chain question

HyperNeutrino

@DJMcMayhem Sure :P Still, make your capitalization consistent >.<

caird coinheringaahing

I found a random regex! ([^0-9a-f?][0-9a-f]+)|([?][^0-9a-f])

I don't know what it does!

HyperNeutrino

Well it selects something that contains two parts I think, ...|...

unless you forgot the brackets around the very outside.

The left part takes anything that isn't 0123456789abcdef? and then any number of hexadecimal digits

caird coinheringaahing

I copied it into regex101, still no idea

New Main Posts

16:50

-3

Q: Sort an array with multiple objects from a file into a new file

I have done Option 1 & 2 but it is not compiling... any ideas on how to fix this? You are going to create a switch loop with different options. Option 1: Ask users to input Person Name, Ticket Type and Fine. You will keep asking users until they press q key. Once user types Q, you will store all...

java

HyperNeutrino

The right side takes a question mark and then anything that isn't a hex digit, unless [?] is different

dzaima

what do I do with this? +3/-2 :|

DJMcMayhem

@LuisMendo status-completed

Cows quack

@dzaima personally I like that challenge so I upvoted it

Step Hen

@WheatWizard hm, that's very interesting, I didn't consider that. Is that a function you made yourself or that you found?

Cows quack

16:58

Also, before seeing that proposed challenge, I had been thinking for some time about a "golf the [numerical] sequence" challenge where people first have to figure out the sequence and then golf it

Wheat Wizard

@StepHen I made it myself. (explanation incoming)

Step Hen

@ETHproductions that thing you added is genius, I think this might be one of the stack snippets that people will save and reuse :P

Wheat Wizard

If you take any current answer you can shift it left or right on the number line pretty easily. That is instead of integers > 0 you can change the domain to >n for any n (I won't explain this hopefully this is evident). So take your function and shift it up to Int_max+1 so that Int_max+1 is the smallest number in the chain, now have int_max+1 map to 1 instead of whatever it mapped to and int_max map to whatever int_max+1 used to map to. This essentially takes the int range and inserts it into an existing chain function, However on the range 1-Int_max it behaves exactly like +1.

If thats confusing I can answer questions.

DJMcMayhem

Ugh. My CnR is at 9.8k views, but it's slowing down. I want that gold badge!

Step Hen

@DJMcMayhem Holds F5 on a different account, you won't get caught I promise

@WheatWizard I understand that part, I was wondering about the function :P

Luis Mendo

17:04

@DJMcMayhem :-)

DJMcMayhem

@StepHen I'm not sure if that technically works

Wheat Wizard

@StepHen That is the function.

Step Hen

@WheatWizard oh, I thought you already had a function implemented that was just +1 on that range and complicated every where else, I was wondering what the everywhere else part was

sorry for the miscommunication

Wheat Wizard

Now I'm confused

I don't even know what the miscommunication was

Step Hen

@WheatWizard I thought you actually had implemented a function that did that and you said if you want to know this function ping me and I wanted to know what that function looked like :P

Wheat Wizard

17:08

I did, Its defined right up there

did you want code?

Step Hen

wait, now I'm confused again, I'm assuming this function is +1 from say 1 to 2^31-1, but after that it jumps back down to one again and does some weird stuff, is that assumption incorrect?

Wheat Wizard

> jumps back down

What do you mean by that?

Step Hen

I dunno how I would implement this but my assumption from what you said was that there is a function that fulfills the requirements such that inside the range is just n+1

say the range cap is 1000

Wheat Wizard

This part is correct "I'm assuming this function is +1 from say 1 to 2^31-1"

Step Hen

My assumption was that once you get above 1000, say, 1001 maps to 1 and then the algorithm does some fancy stuff to get 1001 covered

Wheat Wizard

17:11

Yes thats what happens

You take an existing infinite chain, you break it somewhere and you insert all the other values in order into the hole

Step Hen

@WheatWizard Sorry that took so long :P thanks

Wheat Wizard

No problem

DJMcMayhem

CMC: Write a function that is bijective for all positive integers. In other words, for all positive N, f(N) is unique and != N && f(f(N)) == N

(if I understand what bijective means)

Step Hen

@DJMcMayhem I believe f(f(N)) == N should become f(f-1(N)) == N where f-1 is the inverse function of f

or is it f-1(f(N)) == N, might be that instead

or they might mean the same thing

Wheat Wizard

@DJMcMayhem The identity is bijective

DJMcMayhem

17:21

@StepHen Oh. Does that mean f(N) == N + 1 is bijective?

Mr. Xcoder

@DJMcMayhem Yes.

Step Hen

@DJMcMayhem Yes, I believe so

Wheat Wizard

@DJMcMayhem Not on the positive integers

DJMcMayhem

Why not?

Step Hen

Nothing maps to 1

Mr. Xcoder

17:22

Bijective means that it has a different result for any different parameter

Wheat Wizard

Bijective means injective and surjective

@Mr.Xcoder No that is surjective

DJMcMayhem

What is injective then?

Mr. Xcoder

@WheatWizard That's mainly injective

Wheat Wizard

Every value in the range is mapped to by a value in the domain

DJMcMayhem

Is there a term that means f == f-1?

Wheat Wizard

17:23

Oh yeah I got them mixed up

Step Hen

@DJMcMayhem the following (as I understand it) is bijective, but does not follow @WheatWizard's challenge because it doesn't allow transversing the integers: x=>x%2?x-1:x+1

@DJMcMayhem It should look like f to the power of -1 but I dunno formatting

Wheat Wizard

@DJMcMayhem That is not true.

Mr. Xcoder

Injective means that f: a -> B, f(x) ≠ f(y), forall x ≠ y

DJMcMayhem

@WheatWizard I'm just asking if that term exists

Step Hen

Involution (mathematics)

In mathematics, an (anti-)involution, or an involutory function, is a function f that is its own inverse, f(f(x)) = x for all x in the domain of f. == General properties == Any involution is a bijection. The identity map is a trivial example of an involution. Common examples in mathematics of nontrivial involutions include multiplication by −1 in arithmetic, the taking of reciprocals, complementation in set theory and complex conjugation. Other examples include circle inversion, rotation by a half-turn, and reciprocal ciphers such as the ROT13 transformation and the Beaufort polyalphabetic cipher...

Wheat Wizard

17:25

@DJMcMayhem No it does not, bijective functions must not be their own inverses, as stephen linked that is called an involution.

Mr. Xcoder

A bijective function f: X → Y is a one-to-one (injective) and onto (surjective) mapping of a set X to a set Y.

Wheat Wizard

/must not/can be not/

DJMcMayhem

Ok I get it

Step Hen

@DJMcMayhem Anyway, JavaScript, 14 bytes: x=>x%2?x-1:x+1

Mr. Xcoder

This one works for all integers higher than 1:

def f(N):
 if int(N**.5)<N**.5:return N**2
 return N**.5

DJMcMayhem

17:26

So x%2?x+1:x-1 is an involution, therefore not bijective

Step Hen

Maps 1 -> 2, 2 -> 1, 3 -> 4, 4 -> 3, ...

@DJMcMayhem uh it's supposed to be bijective, dunno if it is or not

but as far as I understand it is

dzaima

@DJMcMayhem JavaScript, 10 bytes: x=>--a^1+1

DJMcMayhem

2 mins ago, by Wheat Wizard

@DJMcMayhem No it does not, bijective functions must not be their own inverses, as stephen linked that is called an involution.

Step Hen

2 mins ago, by Wheat Wizard

/must not/can be not/

Mr. Xcoder

CMC: Given two positive integers, determine whether they are coprime.

Wheat Wizard

17:29

Bijections can be involutions, but they don't have to be

DJMcMayhem

So an involution is a special case of bijectivity?

Step Hen

@WheatWizard And no involution is valid on your challenge, correct?

Wheat Wizard

@StepHen No

Step Hen

@DJMcMayhem I don't think so, f(x) = x is it's own involution

Wheat Wizard

@DJMcMayhem No functions can be involutions and not be bijective

@StepHen f(x) = x is bijective.

Step Hen

17:31

oh right I'm dumb

New Sandboxed Posts

0

A: Sandbox for Proposed Challenges

Challenge: Calculate the largest factorial of integers (!). A factorial (!) of an integer number (n) is defined as the following, all the integers from 1 to "n" multiplied together, so 6! = 1 * 2 * 3 * 4 * 5 * 6 = 720. Factorials quickly balloon in size such that asking a computer program to cal...

Wheat Wizard

an example would be f (x) = x from the positive integers to the integers.

Its is an involution but there is no way to get a negative number out of it.

Mr. Xcoder

Anyone here good at Chemistry (or Physics)?

Step Hen

@Mr.Xcoder define good

Wheat Wizard

I was a physics major for 2 years.

Mr. Xcoder

17:33

@StepHen Being confident with their knowledge in the field

Wheat Wizard

So I'm ok at physics, no good at chemistry though

Step Hen

@Mr.Xcoder I did ok in high school chem but I've forgotten it all, so count me out

Mr. Xcoder

I'm looking for a Chemist this time though

Step Hen

Wheat Wizard

I've only taken high school chemistry so I don't know If I can be of help

Step Hen

17:34

TIL SE sites themselves can onebox

Mr. Xcoder

@StepHen Too dumb for an SE Site, I'm 14

@WheatWizard High school is what I need

Step Hen

@Mr.Xcoder Trust me, they'll be OK with it

Chemistry Stack Exchange is a question and answer site for scientists, academics, teachers and students

Wheat Wizard

Whats the question? Instead of speculating we can know.

If its not about ppcg you should probably ask there though

Step Hen

^^ boring onebox 0.o

Wheat Wizard

Ours looks disgusting

Mr. Xcoder

17:36

NVM

Wheat Wizard

its really blurry on my monitor

Step Hen

@Mr.Xcoder now we're really curious :P

Mr. Xcoder

@StepHen Lemme write it

betseg

when will we get a design

Step Hen

@betseg soon TM

Cows quack

17:37

we'll get our design in November 1st

I thought you knew :P

Step Hen

@Cowsquack source?

Mr. Xcoder

My Q was: What are the coordinative bounds between Nitrobenzene and Ammonium Hydroxide?

betseg

@Cowsquack oh it wasnt last year's nov 1? ohhh

Mr. Xcoder

I don't need the answer anymore, Nvm ^^

Cows quack

@StepHen codegolf.meta.stackexchange.com/questions/5828/…

Mr. Xcoder

17:41

Anyone – Jelly Hypertraining?

Or Pyth?

At least, Is someone willing to write an easy CMC, then?

betseg

CMC: increase inputted integer by 1

Mr. Xcoder

@betseg Pyth, 1 byte: h

@betseg I didn't mean that easy

BlackCap

Print current time

programmer5000

@betseg JS: x=>x+1

Mr. Xcoder

@BlackCap Pyth, 3 bytes: .d0

Cows quack

17:44

@betseg guess the lang, 1+⊢

programmer5000

Is this ready to post? It's at +2/-0 and all issues pointed out in comments have been fixed.

3

A: Sandbox for Proposed Challenges

code-golf cops-and-robbers Will it halt? Cops: This is the cops' thread. The robbers' thread is here. Your challenge is to make a program that runs forever without halting1, unless it gets a particular input or inputs2. If it receives that input, it must terminate in a finite amount of time3....

betseg

@Cowsquack dyalog apl

Cows quack

+1

Mr. Xcoder

Another one?

Cows quack

@betseg Java, class A{public static void main(String[]a){System.out.print(Integer.parseInt(a[0])+1);}}

Mr. Xcoder

17:46

@betseg Jelly, 1 byte: ‘

Cows quack

untested

behold the verbosity

dzaima

@Cowsquack that adds two arguments, not increases one

betseg

@Cowsquack x=>x+1 ?

BlackCap

main=readLn>>=print.succ

Cows quack

I messed up

programmer5000

17:47

3 mins ago, by programmer5000

@betseg JS: x=>x+1

betseg

also java too

Cows quack

@betseg Java lambdas use -> arrows

betseg

oh

BlackCap

Print every other letter from the input

Mr. Xcoder

@BlackCap every other?

What is other here?

Cows quack

17:49

where do we start?

BlackCap

print letters at even indecies

Mr. Xcoder

@BlackCap Ok

BlackCap

befunge, 4 bytes ~~$,

dzaima

@BlackCap 0-indexed or 1-indexed even?

BlackCap

zero indexed

Mr. Xcoder

17:51

@BlackCap Pyth, 2 bytes: %2

I gtg, will be back shortly

dzaima

@BlackCap SOGL, 4 bytes: 2nHk

BlackCap

caird coinheringaahing

omg. I just went over to Movies & Tv and saw that one user (not saying who) got suspended for a year. That is too long.

totallyhuman

um ok?

BlackCap

Did he share an entire movie?

caird coinheringaahing

17:54

@BlackCap no but he's had a string of long suspensions there

Cows quack

@BlackCap will the input string always be of even length?

BlackCap

You may assume that

or that the input is infinite, if you wish

Cows quack

sed, 11+1 bytes, s/(.)./\1/g

betseg

C++ lambda: auto f=[](int a){return a+1;};, C++ function: int f(int a){return a+=1;}

lambda is longer

totallyhuman

lambda s:s[::2]

if it's the wrong indices: lambda s:s[1::2]

BlackCap

17:58

Remove even lines

caird coinheringaahing

@BlackCap you went from one horrible sequence to another ಠ_ಠ

BlackCap

Is it that bad?

caird coinheringaahing

yep

Cows quack

sed, 19+1 bytes, Try it online!

caird coinheringaahing

If the OEIS page doesn't give a(n), its bad

BlackCap

18:00

I should learn sed.

totallyhuman

large (it's big, don't download on restricted data) awesomeness

Mr. Xcoder

Yay, even indexes in a String? Pyth wins by far (if jelly doesn't outgolf it)

@cairdcoinheringaahing Want to join Hypertraining?

betseg

i've just noticed that i passed 6k

Mr. Xcoder

@betseg Congrats! I just passed 5k :D

betseg

nice emoticons

New Main Posts

18:06

2

Q: Verify Topology

Challenge Given a set T of subsets of a finite set S={1,2,3,...,n}, determine whether T is a topology or not. Explanation The powerset P(S) of some set S is the set of all subsets of S. Some examples: S = {}, P(S) = {{}} S = {1}, P(S) = {{}, {1}} S = {1,2}, P(S) = {{}, {1}, {2}, {1,2} S = {1,...

code-golf math decision-problem set-theory topology

Mr. Xcoder

@betseg Couldn't really decide

Erik the Outgolfer

@Mr.Xcoder he's already in

Mr. Xcoder

@EriktheOutgolfer I asked him if he wants to train with me now.

@EriktheOutgolfer Do you want to teach me a bit?

totallyhuman

yurt

Erik the Outgolfer

@Mr.Xcoder come over

Mr. Xcoder

18:08

@EriktheOutgolfer Already there

ETHproductions

18:22

@StepHen The available/not-available thing, you mean? Yeah, I liked how it was fairly easy to tell in the old version whether a byte count was used, so I wanted to have something similar in the new version

New Sandboxed Posts

0

A: Sandbox for Proposed Challenges

What's the check? code-golfset-theory Quick! You need to give some check, but you don't have time, as customers are waiting in a queue. Fortunately, you can make a program that can do the job for you, but, since you don't have much time to write it, it must be as short as possible. Also, due to...

Erik the Outgolfer

@NewSandboxedPosts wow 14 minutes that's quick as hell!

Riker

18:54

@DJMcMayhem arxiv.org/pdf/1412.0784.pdf

about how braid is undecidable, TC, and a couple other things

DJMcMayhem

Woah

Christopher

@HyperNeutrino i found the problem with the handler. Your bots don't work

DJMcMayhem

@Riker BRB, making braid esolang :P

Cows quack

braid-flak

4

DJMcMayhem

Yeaaaaah

Christopher

19:00

No-Flak

HyperNeutrino

@Christopher well rip I will try to fix them

Christopher

@HyperNeutrino Yeah make it a real function

HyperNeutrino

Is the issue that I'm using lambdas rather than real functions?

Christopher

Yeah

You do nothing at all and the entire thing breaks

HyperNeutrino

done

Christopher

19:08

Ty man

HyperNeutrino

np

Christopher

Going to get current standings

HyperNeutrino

yay

Christopher

Lol CautionBot vs agressor. Agressor lost 20-0

HyperNeutrino

lol xD

hey I got sportsmanship xD

Christopher

19:14

Actually aren't they only supposed to play 10 rounds?

HyperNeutrino

well the way I have it, they play 10 rounds with the left bot starting and 10 with the right bot starting

change 10 to 5 if you want just 10 rounds

Christopher

ohh

That makes sense

huh

totallyhuman

Yurt

Hi

Christopher

I am half way into the new Red vs blue episode. IMMA BOUT TO KILL ONE OF THEM WRITERS

totallyhuman

I'm two answers to 150

Christopher

19:37

@HyperNeutrino random bot is annoying

like super annoying

every other bot it is simple

but random bot SCREWS SCORING UP

totallyhuman

D: D: D:

hey i can't find the text 1337ify challenge

there's gotta be one right?

ETHproductions

Programming question: I had the brilliant idea of a data type that could represent multiple values at once (e.g. so a function can return multiple values in an easier way than an array), but before I get all excited about my new invention... isn't this the basic idea behind tuples?

totallyhuman

CMC: 1337ify text

Christopher

English 1 byte: ^

totallyhuman

no what?

Christopher

19:42

@totallyhuman What?

ETHproductions

What's the 1337 alphabet again? 1 is l, 3 is e, 7 is t...

Christopher

a = @

New Main Posts

0

Q: Secret Message Part 1, Elements

You and your friend want to send each other secret messages. However, because you are conspiracy theorists and think that the government has a quantum computer that can crack any standard encryption. Therefore, you are inventing one of your own. The first step of this is as follows: taking an ...

code-golf string encryption

Step Hen

@ETHproductions I believe so

29

Q: Return multiple values from a Java method: why no n-tuple objects?

Why isn't there a (standard, Java certified) solution, as part of the Java language itself, to return multiple values from a Java method, rather than developers having to use their own means, such as Maps, Lists, Pairs, etc.? Why does Java not support n-tuple objects? Especially thinking for tri...

java methods return-type

ETHproductions

This webpage I found seems to think that in Python tuples are basically supposed to be dicts, but using indexes instead of keys

BlackCap

19:47

@ETHproductions No, that sounds like non-determinish. Curry does that

Step Hen

@ETHproductions o, I thought tuples were for heterogeneous data

754

A: What's the difference between lists and tuples?

Apart from tuples being immutable there is also a semantic distinction that should guide their usage. Tuples are heterogeneous data structures (i.e., their entries have different meanings), while lists are homogeneous sequences. Tuples have structure, lists have order. Using this distinction ma...

totallyhuman

abcdefghijklmnopqrstuvwxyz -> 48cd3f6h1jk1mn0pqr57uvwxyz

BlackCap

@ETHproductions Touples can contain different types of data in a typed language

ETHproductions

@StepHen Ah, that makes sense

Step Hen

@ETHproductions (of course that's all just semantics and you can do whatever you want)

since if you're never going to change it a tuple is better than a list even if the tuple is homegenous

Biggest thing is tuples are immutable, at least in Python

ETHproductions

19:50

y tho

Step Hen

@ETHproductions Why immutable? or why better

ETHproductions

right

Step Hen

I dunno

ETHproductions

Is it just to reinforce their intended purpose I guess?

So you can't just append items to the tuple ad infinitum

Step Hen

More efficient

and you can use them as keys in dicts then

ETHproductions

19:52

Yeah

Anyway, I should get going. Thanks for the discussion :)

Step Hen

No prob, see you around

ETHproductions

@BlackCap If you didn't notice, I added another OEIS answer so it's open to you again

BlackCap

An easy one too

nobody take it please, I'm gonna find some really obscure esolanguage

Step Hen

@BlackCap easy? how would you implement it? seems kinda complicated to me

@BlackCap You see it has no 14, 30, etc. right?

BlackCap

right.

curry: s = x^2+y^2+2*z^2 where x,y,z free

Transcript for