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10:02 AM
... Stack?
Yeah, I already have the obvious ones, stack, tape and registers
How is "register" a memory model?
"register and RAM"?
Grid? (like Hexagony memory model, but not necessary hexagonal grid)
@user202729 As in integers that can interact with each other via commands, but aren't stored in a tape/stack (i.e. a set number of registers)
@user202729 Yeah, grid and deque are the other two I've got
@cairdcoinheringaahing Infinite integers? Creating data structures in such a language would be hard.
@user202729 Infinite as in arbitrary precision?
10:06 AM
(otherwise it's not TC)
@LeakyNun so the function takes in a (nat → bool) function and returns a nat, or does it take a nat and bool and return nat`
@Cowsquack the former
(the latter would be (nat x bool) -> nat or nat -> (bool -> nat) :P
But what is "nat"?
@user202729 yes
@user202729 natural numbers
How is this decidable? ....
10:14 AM
it is :P
can you give examples?
So a (nat -> bool) is equivalent to a subset of nat...
and a (nat -> bool) -> nat maps each subset of nat to a natural number.
There are uncountably many subsets...
@Cowsquack so an example of (nat -> bool) -> nat would be λ t, if t(0) then 1 else 0
@Downsheep keep value, cast isn't bitcast. it should throw exception or something if out of range
@user202729 right
10:16 AM
@Downsheep idk, it isn't in any doc?
@LeakyNun so if the input to (nat → bool) is 0, then (nat → bool) → nat gives 1
I think the strategy is to pass a specially constructed t into the box and...
@Cowsquack wait what
if the given function nat -> bool returns true when I input 0, then I return 1
(i.e., for that example, it maps all subsets containing 0 to 1, all other subsets to 0)
10:19 AM
>> f=t=>t(0)?1:0
<< t=>t(0)?1:0
>> f(k=>k>3)
<< 0
javascript demonstration
@LeakyNun of yeah because (nat → bool) → nat doesn't know what the first nat is
Must the function t passed in be pure?
@user202729 yes, guaranteed to halt at every input and give bool
I meant the nat -> bool passed as input.
10:21 AM
Wait a minute, how is "guaranteed" related here?
@user202729 yes, halting at every input and give bool
@LeakyNun is this actually doable in a finite amount of time
@Unicode-only yes
(for example, can the function passed in be input => {global list.push(input); return 1;})
10:27 AM
@user202729 does it have a turing-machine equivalent?
so basically you need to pass in a function/functions to determine the entire code of the functions, or pass in a set of functions that cover every combination of inputs?
what do you mean?
Pass in a function (nat -> bool).
@Unicode-only Why are you still Unicode? Even the duck has left SE
you need to somehow be sure they do the exact same thing. so you need to somehow figure out either 1. what they do, or 2. cover all possible cases
@cairdcoinheringaahing sheep and bald star trek dude are still here, but good point
10:31 AM
passata changed back...
@cairdcoinheringaahing better?
@user202729 sorry brainfart
@ASCII-only Much :P I can type your name now :P
@ASCII-only "bald star trek dude" facepalm
help my avatar is still broken
Help why does TIO interpret J input as commands
IIRC the input is fed to the repl
@user202729 you could say the same about APL
so that's why
But how can I read stdin then
@ASCII-only A special keyboard is enough. I don't need two.
Exit code 100 -- argument list too long.
10:35 AM
@user202729 you're given two functions (nat -> bool) -> nat
I will do that later...
@LeakyNun if the (nat → bool), say, only returns true if nat is above 1E100, then what are you going to do
@Cowsquack But that's finite...
@Cowsquack you aren't given a function nat -> bool
don't you have to check for every n ∊ nat?
10:37 AM
@Cowsquack you aren't given a function nat -> bool
The naive algorithm is to check for all (nat -> bool)
@Cowsquack you pass the function in
and there are uncountably many.
and that function takes in a nat
10:37 AM
@Cowsquack yeah the function you pass in has to be nat -> bool
takes in nat, returns bool
oh I see
then you pass nat=>!nat to the functions and test for inputs 0 and 1
the CMC asks you to write a function of type ((nat -> bool) -> nat) -> ((nat -> bool) -> nat) -> bool
@Cowsquack what does that do
to clarify any ambiguity
@LeakyNun wait. so you only have the composition of f and g???
10:42 AM
@ASCII-only if the outputs are the same then you know they're the same
@ASCII-only composition?
I guess you have to explain lean's notation
I mean
(((nat -> bool) -> nat) x ((nat -> bool) -> nat)) -> bool
I don't think there's any ambiguity here
@Cowsquack What does ! do in this case?
give false if 0, true otherwise
10:45 AM
.... So, because it's guaranteed that both f and g hatls, they must only examine finitely many inputs in all cases.
@user202729 that's true. but we're probably trying to find a better solution than every possible combination :P
@ASCII-only Every possible combination will run infinitely.
So find any solution that will evantually halt is strictly better.
@LeakyNun does my function work?
where's your function?
@Cowsquack What's your function?
Although I already asked this, I don't understand the answer.
Can the (nat->bool) that **we** pass into the **given** f and g be impure?
10:51 AM
equals←{(g∘¨≡f∘¨)(not 0 1)}
@Cowsquack not 0 1 seems redundant
input functions are f and g
@Cowsquack Translation to other languages please?
@user202729 I don't think so
otherwise it wouldn't be a function nat->bool
does it work LeakyNun?
or am I still misunderstanding something
10:54 AM
I can't understand your code
I can't understand your code
@H.PWiz now that I look into it, f and g take in a bool, so would I have to do f∘not and g∘not?
@Cowsquack g and f should each be operators, not functions (in APL speak)
They take a functional argument
Q: Zero-sum counting

orlpWrite a program or function that given n ≥ 1 returns the number of solutions to ±1 ± 2 ± 3 ± ... ± n = 0. For n = 6 there are no solutions, so the answer is 0. For n = 4 there are two solutions, so the answer is 2 (the two solutions are 1 - 2 - 3 + 4 = -1 + 2 + 3 - 4 = 0). This is OEIS sequence...

@Cowsquack What...?
No, f and g take in a nat->bool.
10:56 AM
I will translate it once I fix it
how do you define an operator dfn again?
@Cowsquack ⍺⍺
oh right, ⍵⍵ was borking
@H.PWiz ∧/(0∘=a≡0∘=b)¨0 1
a and b are operators
translation: so let's call the two ((nat → bool) → nat) functions a and b
this feeds the function f=x=>x==0?true:false into a and b
@Cowsquack I don't think that s valid. Let a←{2×⍺⍺ 2} and b←{3×⍺⍺ 2}. This says that they are equal
11:06 AM
and gives the input 0 and 1 to (a f) and (b f)
ah I see
@orlp nice
very clever
12:04 PM
@LeakyNun Huh? ...
@Cowsquack x==0?true:false ...
Almost as bad as a
switch (boolean_variable) {
case true:
// ...
case false:
// ...
I wanted to make it explicit, because you asked what !x was
Anyway, I also don't think that they're valid.
But I still feel that this is unsolvable.
@user202729 yeah, HPWiz already said that
Let's say, if our function A is given f == g == (x => 1) and returns true, we can record the (finite) set S of (nat -> bool) functions fed into f.
And then give A the function f == (x => 1), g == (x => (if there is any function (y) in (S) that coincides with (x) the first (n) values then 1 else 0))
where n is the first value such that 2^n>|S|
then g != f and our function can't determine that.
12:40 PM
@user202729 what
12:53 PM
@user202729 why not use !x as an example instead?
> (x==0?true:false)?false:true
1:34 PM
Is my reasoning wrong? That appears to prove the function is uncomputable.
..oh, i didn't scroll down
A: Sandbox for Proposed Challenges

The random guyFind me in Pi codegolfpi Challenge : Pi is supposed to be infinite. That mean every number is contained inside the decimal part of pi. Your task will be to take a positive number on input and return the position of this number in pi digits on output. For example, if the input is 59, we'll ret...

(@LeakyNun )
1:53 PM
@user202729 could you elaborate on why our function can't determine that?
Slight mistake. the set of S are the functions fed into g, not f.
Because... A only give g the functions in S, so all of its output are 1.
And because there are more possible tuple of boolean values y(1),y(2),...,y(n) than number of functions in S, there exists a tuple that isn't in those produced by a function in S, so there exists a function that g returns 0.
Ha, I've had a total of 299 stars on my messages in TNB :P
don't star one more or it would be 300
2:01 PM
@user202729 too late
@cairdcoinheringaahing congrats on the 300 stars :p
Should probably be a badge or something
It seems better to star my existing message on the starboard, rather than a totally new one, that will probably only get one star :P
Now there are misinformation on the starboard. @J.Sallé Your fault.
(actually outdated information)
I regret nothing
@J.Sallé Given Dennis has >4500, I think 300 is nothing :P
@cairdcoinheringaahing well, he should have 15 of those badges then >.>
2:05 PM
Ugh, had to disconnect my primary screen, when got it back it doesn't detect any sources. Windows does detect it, can read it's resolution and seems to send signals to it, but the screen doesn't react. No buttons on the screen help, because they require signal to be sent to it first (which is completely stupid, you can't configure it without source, you can't even change the source). I tried unplugging both the primary and secondary string, but no success.
@J.Sallé 1000 stars seems more likely to be a badge, given that only 20 PPCGer's have that in TNB
Fair enough
@J.Sallé I support this idea.
Q: Pi got your number

The random guyChallenge : Pi is supposed to be infinite. That mean every number is contained inside the decimal part of pi. Your task will be to take a positive number on input and return the position of this number in pi digits on output. For example, if the input is 59, we'll return 4 Here is why : we wil...

A: Sandbox for Proposed Challenges

simonalexander2005Title: Lossless "Compression" Implement the following lossless pseudo-compression pseudo-algorithm and its decompressor; scored by the number of bytes after you've put your source-code for both through your own implementation of the compressor algorithm, described below: Algorithm Description ...

2:18 PM
@user202729 Because if you don't exit your program (with, e.g., exit ''), the J interpreter drops to a REPL at the end of it, so unconsumed input will be treated as REPL commands. STDIN still works though.
CMC: Output 26 without numbers in your source code
Jelly: ØAL. Pyth: lG.
Whatever this language will be called: #++[>+[>+++<-]<-]++,>>,
”<26th char here>O
@cairdcoinheringaahing zl or '⁸ in SOGL
2:29 PM
Doesn't work.
@cairdcoinheringaahing V, 5 bytes: ¬azø.
Port of Dennis's solution
@cairdcoinheringaahing Brachylog, 2 bytes: Ạl
Does someone know how to make a code block with an empty last line?
@wastl Use <pre> tags (like so‌​)
in where? SE? Yes, but be careful to escape < and >.
2:32 PM
@cairdcoinheringaahing APL (Dyalog) 3 bytes: ≢⎕A
(&lt; and &gt;)
@wastl Use the auto-formatter on TIO. Also works for lines containing only spaces/newlines.
Can anyone spot any improvement in this answer? (Haskell)
@Dennis When I use that, it shows the trailing empty line in the preview when I go to post my answer, but it disappears once the answer is actually posted.
2:46 PM
You might have to disable syntax highlighting for that post.
Ah, that makes sense
@Downsheep what's :> in VSL, I see it reserved
That's clearly the evil operator.
Is it just me, or linking this right in my answer feels a bit rude? Not that I really care, but I'm a bit surprised
Yeah, that seems a little arbitrary, and more of a better fit under the challenge
2:50 PM
... sorry
No problem! I just had never seen that linked directly in an answer
as if saying "this answer is crap" :-)
I was going to reply to Therandomguy's comment above, but I think that
it can be useful for someone else.
@cairdcoinheringaahing only 200 stars?TNBDE says I have like 2100
here, try this query:
@quartata I have been only around for 13 months :D
select sum("transcriptAnalyzer_message".stars) from "transcriptAnalyzer_message" left join "transcriptAnalyzer_user" on "transcriptAnalyzer_message".user_id = "transcriptAnalyzer_user".id where "transcriptAnalyzer_user".uid = <your chat id>
2:56 PM
no it's a good thing
Aww, 296, I was off by 3 :/
+1 for lowercase sql.
Screaming while programming will distract your coworkers.
it's probably just out of date
anyways, I wonder if it's because of a few highly starred messages or many one starred messages
Dennis has 4500 o_O
2:59 PM
@quartata My stars range from 1 to 23, so its a bit of both, by the looks of it :P
5/7 lowercase sql is the only possible sql
Are we sure that's correct? I'm not even here that often.
@Dennis Yeah but people star your messages all the time pretty much at random
@Dennis What does this look like for you? I'm guessing lots of 10-30 star posts
@Pavel Case in point :D
Still, I've posted just over 27,100 messages. That's 0.17 stars per message.
3:03 PM
I only have 31 stars, ranges from 1 to 5.
@Dennis Not if I've already conditioned them to accept my workflow
CMP: What's your most-starred message?
Mine with 23
How can I tell?
Dennis has too many starred messages that finding manually is too tedious.
I'm at 24 on this
Q: ASCII-art to numbers

wastlInspired by Digits in their lanes Input: An ASCII-art of width ≤ 11, consisting of spaces and #. (You can choose any two distinct characters instead.) Example: # ### # # # # # # # # # ### # # ### # ########### # # # ...

@Dennis I just checked the starred messages posted by me, and scanned over them. Not sure if that'd work for you though :/
I have too many starred messages to dig through them all.
@cairdcoinheringaahing There's 22 pages.
Maybe TNBDE might help?
3:08 PM
It's probably this one, at 57 stars.
Dec 19 '16 at 2:24, by Dennis
The next person who abuses his privileges to get hats will get a suspension instead, until the day after Winter Bash.
@cairdcoinheringaahing I have zero SQL skills.
2 stars. Also no one did solve it (it's pretty easy)
Close third(?) was, sadly, posted for the same reason.
Dec 16 '15 at 23:08, by Dennis
Hats are fun, but reopening questions that should remain closed, just to collect a hat, is taking things too far. Please refrain from doing this.
Aug 2 '17 at 16:55, by DJMcMayhem
user image
With 25
CMC: TNBDE query to determine average star count per message for all users sorted greatest to lowest
No onebox please
3:12 PM
Aug 2 '17 at 16:55, by totallyhuman
and that is the 25000th starred message :D
@DJMcMayhem that image is gold
@Poke (edit ninja'd)
@J.Sallé thanks
@Pavel It'll almost certainly end up being someone with the fewest messages
I just want to see if it's Dennis
3:15 PM
That's the first time I've flagged a chat message :P
Glad that's over with
What happened? Spam?
@Pavel Dennis has posted 54145 messages in chat... I have a hard time believing he'll have a high average
3:21 PM
That's all of chat btw. Roughly half of them were posted here.
A: Sandbox for Proposed Challenges

Olivier GrégoireBinary path For an integer n that satisfies n > 0, write its value as a right-descending path based on its binary representation. Rules The first set bit (most significant) is always in the top-left corner. When the next bit is set (a 1), draw with a character on the next line in the same col...

I'm planning on posting this in the next hour, any last thoughts? Is everything crystal clear?
A: Sandbox for Proposed Challenges

user56656(A → B) → (¬B → ¬A) proof-golf Well I think it is about time we have another proof-golf question. This time we are going to prove the well known logical truth (A → B) → (¬B → ¬A) To do this we will use Łukasiewicz's third Axiom Schema, an incredibly elegant set of three axioms that are comp...

... and posted
> This account is temporarily suspended network-wide. The suspension period ends on Mar 31 '28 at 15:17.
Regarding the troll ^
That's a nice "temporary" suspension.
I wonder if stackexchange/stackoverflow will still be the goto in 10 years
3:38 PM
My thoughts precisely.
Q: (A → B) → (¬B → ¬A)

user56656Well I think it is about time we have another proof-golf question. This time we are going to prove the well known logical truth (A → B) → (¬B → ¬A) TeX To do this we will use Łukasiewicz's third Axiom Schema, an incredibly elegant set of three axioms that are complete over propositional logi...

@J.Sallé First rule of suspensions is that we don't talk about suspensions, as cliché as that sounds
@NewMainPosts In the URL: a-→-b-→-¬b-→-¬a
@cairdcoinheringaahing I just thought the wording was funny. I'd never imagine something "temporary" to be 10 years long, but it does make sense, of course.
4:17 PM
Someone should write a challenge on this:
@NewMainPosts So the point is to prove that the third axiom is not an implication, it's a biconditional?
A: Sandbox for Proposed Challenges

l4m2Text -> Brainfuck Well I just can't find it and post here waiting for someone mark it duplicate

@NewSandboxedPosts ಠ_ಠ That's just lazy
But it's a dupe anyway (right?)
It's been done with brain-flak, but I don't know if it's been done with brainfuck
(and the two are radically different)
4:22 PM
@user202729 it is
@totallyhuman In essence yes.
but we haven't defined what a biconditional is so you just prove it going the other way.
@cairdcoinheringaahing Putting effort into a something that will soon be deleted sounds like a waste too.
@user202729 If you look at it that way, isn't this entire site a waste?
How is "this entire site" related to "soon be deleted"?
Also... participating on the site is fun.
(depending on your definition of "waste", it may be)
Are chat suspension site-specific or network-wide?
Almost nothing on this site has any real impact, we're just a bunch of people writing horrible code for fun. We are, essentially, wasting our time. However, we can choose to waste our time effectively and making the site pleasant for others, or we can post one liner posts that mean nothing to anyone else, and take up space for others. Most of us, thankfully, choose the former
@user202729 Network wide IIRC
4:29 PM
Sure, posting lazy challenges on main is bad, but not in the sandbox.
Why isn't it bad in the Sandbox?
@cairdcoinheringaahing well, I've learned a bunch of stuff while "wasting my time" here. Mostly APL but a lot of logic as well.
The whole point of the sandbox is to post incomplete or need-review challenges...
So that's not a waste in my books.
@J.Sallé Fair point
4:31 PM
In this particular case the OP is just asking "if this is a dupe I will delete it" something like that.
@user202729 Incomplete, not "needs a complete rehaul to be considerable on main"
@user202729 Then ask if said challenge is a duplicate in chat, before posting. Or go find the duplicate yourself, especially when it's that blatant
@user202729 Yes, but it's not the place to say "Hey, is this a dupe?" without speccing the challenge at all. That's what chat is for
Also, ninDJ'ed again
It particularly irks me when people treat the sandbox as a dumping ground: "Oh, it doesn't need to be totally finished before I post it here, so I'll just post the bare minimum I can get by with and edit it later". Seems lazy and unproductive to me
@DJMcMayhem @cairdcoinheringaahing Not everyone knows about chat. Of course. Saying "that is what chat is for" is not a reason.
4:33 PM
The most effective way to use the sandbox is to write it up entirely as if you were about to post it, and then look for minor loopholes or inconsistencies
@user202729 I4m2 has been, and talked, in chat before
search chat messages Again, not a reason. Although in this particular case...
Not a reason for what?
5:09 PM
Announcement: APL Cultivation in 20 minutes.
@DJMcMayhem can n be taken in unary?
(likewise can output be given in unary?)
Given that I haven't thought about that CMC for like a year, I'll go with yes
whoops, I saw someone reply to that cmc and thought it was recent >_>
oh I see, I clicked on wheat wizard's most starred message and found a cmc nearby
Customer: Feature X sucks. Can it be made better?
Me: *works on feature overhaul for 2 weeks, achieves perfection*
Customer: Cool! But the font is kinda small even though it's the same exact font used basically everywhere else - can it be made bigger?
Me: *considers day drinking*
@cairdcoinheringaahing that’s not true. While most things here don’t have direct impact, I’ve developed so many valuable skills here. With those skills I have been able to create things that have an impact and I’m sure others have too
5:25 PM
Making Seriously/Actually and PPCG v2 made me git gud at unit tests, which impressed my now-boss when I was interviewing for my current job
6:06 PM
@Mego Did you not unit test before?
@Mego my life in a nutshell.
@Pavel they take a respectable amount of effort to enact, which ppcg is not known for encouraging
I'm developing an application that makes financial reports based on the systems the company I work for sells. The whole point of the application is so our clients don't need to use excel for this kind of stuff anymore.
First meeting with the client:
C: "Can we get an 'Export to Excel' button?"
Me: *facedesk*
that sounds very saddening
7:07 PM
and took over the entire map
..highway doesn't handle it's two sides meeting very nicely
literal river of ants
7:26 PM
Q: (A → B) → (¬B → ¬A)

user56656Well I think it is about time we have another proof-golf question. This time we are going to prove the well known logical truth (A → B) → (¬B → ¬A) TeX To do this we will use Łukasiewicz's third Axiom Schema, an incredibly elegant set of three axioms that are complete over propositional logi...

I'm looking at this question, at the example
A → (B → A)                                     L.S.1
A → ((B → A) → A)                               L.S.1
step 1 is logical, it directly introduces axiom 1
but step 2 I'm at a loss
how does axiom 1 give that?
Let (B → A) = ψ
but you don't have (B -> A)
So, why would you need (B → A)?
I thought you did
for deduction
Nope it can be any statement
7:30 PM
that it's substitution of what you already have
makes sense in hindsight
@J.Sallé I feel you; I'm doing something similar, working on insurance products, doing all this stuff to dynamically evaluate risk and all the users want is a static PDF or a powerpoint deck
I'll make it clear in the question.
Q: Remember the Tower Bloxx?

nicaelI have recently thought of a wonderful relatively old mobile game, called Tower Bloxx. Alhough I'm not really old myself, but it reminded me of childhood and school :) So this my challenge is a kind of a reference to that good game! I have (hopefully) looked into any tower question on PPCG an...

8:28 PM
Q: Integers in Base Pi

mbomb007Background: Pi (π) is a transcendental number, and therefore it has a non-terminating decimal representation. Similar, the representation doesn't terminate if written in any other integer base. But what if we wrote it in base π? Digits in decimal represent powers of 10, so: π = 3.14… = (3 * 10...

Q: Paint Starry Night, objectively, in 1kB of code

NathanielNote: Anders Kaseorg has been awarded the accept for now, to draw attention to his great answer, but the challenge is by no means over! There is still a 400 point bounty in the offering for anyone who takes the top score without using built-in compression. Below is a 386x320 png representation ...

Question: if I want to bind page up/down to mouse scroll wheel, how might I do that on Linux? I know of AHK on Windows.
@NewlyFeaturedQuestions wow, that's nice of the guy
@user56656 I don't know how long you're expecting solutions to be for the proof-golf challenge, but my unfinished solution is currently too big for the Prolog program to read it. Admittedly, I have gone round the houses a bit, but it's not that long
Oh no. could you send me the proofgram so I could try to debug the Prolog?
8:41 PM
It appears to just be a size issue. see https://tio.run/##7VXbbtpAEH3nK7aWKnbVsVWSt7YgmUoVlagS1XlwBMhxwwKWjG3ZG2hF8u10xmvHFxzaD0BI9u7MOWdmdmdMksZhvDazfXA8@ire8tnk@W4hmGmO2GyygMNjvJSe@pNIPgE/TDa@eIEceCesXsH4B97q9faZRiyscskNZnw25soQsM8QEcWKu1rHMA20QaZ8JbcyUh46EBGsuAv3GtLwEdgwR23SPZLev0G616Qv3ZFq@7xCV2iBYmPVATpv7dfrhruIXxTG83CFLc9AGA242wCeVknwCt9UbyjXVEvRDkEU@@UvvQo6K68SL6rlcau@cPGe3flw8PEFmiDqiV6YDcqQB3eIKdmUlwe2wNapZ2Uh9KoJLdFj@CoElIZxvrTJ1iFxfSJB92ALoNdYy4y7ovdSmSkvXnlhEMnXytgBn2w@ZA/z6OEFWB1knVKMeUR3kqQBnmqmZMIdtVXg4EqwTyZLNqmfSV5FJrcA5qgUn9RRHo1MhuXlpn0aKEnZb/0kDDLFc4PWgyiEdxhs54fBUgdzwdP
@cairdcoinheringaahing Charcoal, 3 bytes: ILα
8:58 PM
@H.PWiz Here:
That should fix it.

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