The Nineteenth Byte

Pavel

00:00

Arm? Why would anyone use Arm? No one likes Arm.

Jan Dvorak

I have two arms. I'd rather keep them, thank you.

user2284570

@JanDvorak : yes, the alternative for answering my question is to have full knowledge of the elf format.

Jan Dvorak

It is well documented, and I only need to generate one valid header...

Pavel

@user2284570 No, one person needs to have full knowledge of the elf format.

Everyone else copies him.

user2284570

@Pavel : arm eabi 5 please :)

Pavel

00:03

You could also create a copy of an existing Elf file and then fill it with nops.

And specify the new size in the header.

New Main Posts

1

Q: Convert λ-expressions to SK-expressions

The λ-calculus, or lambda calculus, is a logical system based on anonymous functions. For example, this a λ-expression: λf.(λx.xx)(λx.f(xx)) However, for the purposes of this challenge, we'll simplify the notation: Change λ to \ (to make it easier to type): \f.(\x.xx)(\x.f(xx)) The . in lamb...

Downgoat

O_O Apparently github API is mixing up stars with wacthers

Jan Dvorak

so does the SE UI

Downgoat

?

Jan Dvorak

I'm talking about the per-site bookmarking feature that SE has, called "favorite"

DJMcMayhem

00:13

@Downgoat You should have it be black/gray until you (star|fork|watch) it, then it turns (gold|blue|purple)

Downgoat

@DJMcMayhem oh good idea

I have question

Pavel

What's your question Downgoat?

Downgoat

current if you click on those, buttons, it shows you all info. (e.g. shows you all stargazers)

How should I add the ability to star too

user2284570

@Pavel :And specify the new size in the header. Along the offset. Yes, you crossed the problematic part. In order to be valid for chrome, the elf file needs to have a.shstrtab. and a .ARM.attributesin the case of armv7.

Pavel

@Downgoat tap to star, tap and hold to see info?

DJMcMayhem

00:15

@Downgoat hmm, good question... Long hold?

Downgoat

I was thinking clicking icon stars it, and clicking text will show details. (text can have chevron at right side)

DJMcMayhem

Ninjad

Downgoat

@Pavel perhaps I could do like twitter and show icons of people who have starred and clicking on those will show all?

Thing is, long hold doesn't have "discoverability" as Apple calls it

DJMcMayhem

Oh, good point

@Downgoat Btw, I really appreciate the sample repo you've been using :D

Pavel

Swipe right on the Stars/Watchers/Forks bar?

Downgoat

00:17

@DJMcMayhem :D cglad you like it

Christopher Peart

@Downgoat make the konami code in goathub

Pavel

It's an iPhone App. Entering the Konami code would be a pain.

Christopher Peart

swipes or when typing you type UUDDLRLRBA and hit enter

ATaco

CMC: Write a Non-cheating Quine with a Prime Character Count.

Jan Dvorak

Meh. I'd have to remember how to golfscript.

ATaco

00:28

Oh Golfscript, there was a time when that was the language to golf in.

Jan Dvorak

At least it was documented ;-)

Pavel

Back when you could still compete on PPCG without needing a special keyboard

ATaco

RProgN would have been competitive!

Jan Dvorak

How about q++, is that a cheating quine?

ATaco

In which language?

Jan Dvorak

00:31

HQ9+

Christopher Peart

It is not cheating

It is a "language"

Here 99 bottles of beer 9

ATaco

It is cheating, q reads directly from the Source Code.

Helka Homba

Anyone know a math website where you can draw basic shapes on a euclidean plane? e.g. "draw a circle with radius 10 centered at 60, 50"

Jan Dvorak

But, your program can't read the source code. It can only output it.

@HelkaHomba yes

that is, if Geogebra counts as a math website

ATaco

Although, Hello, World! is a non-cheating quine in H9Q+, ironically.

4

Helka Homba

00:35

@JanDvorak Yes! Thankls

ATaco

And is 13 characters, thus making it a prime-quine.

DJMcMayhem

00:47

@ATaco ñéÑ~"qplllÿ

The 3 'l's are random noops to pad it to a prime length

Riker

00:58

@user2284570 add a brief explanation of an elf?

@HelkaHomba desmos is also nice

Pavel

01:13

@HelkaHomba Wolfram Development Platform

Riker

@flawr r/1sentencestories

Pavel

@Riker Can't you PM each other this stuff >_<

Riker

but why?

it's 1 msg, and other people in tnb might also like it

@ATaco it's not valid by our rules though

iirc it has to be payload capable or smth

New Main Posts

0

Q: Palindromic Quine Polygot

Create a piece of code that runs in as many different languages as possible, and is palindromic (the same forwards and backwards), and prints its own source code. This challenge is scored by how many languages it runs correctly in. Major versions of languages can be counted as different languag...

quine palindrome polyglot

Pavel

@Riker No, there has to be a part of the code that can be identified as encoding another part of the code.

Riker

01:22

yeah but it also has to be payload-capable iirc

Pavel

No

ATaco

That's debated.

Dennis

@ATaco Nope, still cheating.

ATaco

I never said it was wrongly debated.

Pavel

Well, there is the fact that HQ9+ isn't a language.

ATaco

01:23

I'd rather 1\n1 not be valid.

Pavel

Do you think 2i2i should be counted?

Riker

@ATaco it's not

@Pavel it is, it's payload capable (mostly)

ATaco

It was, for a time.

Riker

I think

<somethinghere>2i<somethinghere>2i

Pavel

@Riker No, it technically is. The second 1 encodes the first one and vice versa

Riker

01:27

10

A: What counts as a proper quine?

Instead of arguing about what counts as a "real" or "proper" quine, which I suspect is too subjective and context-dependant to ever permit a non-contentious definition, let me try to instead suggest a related, hopefully slightly less loaded dichotomy: Definition: A quine is payload-capable if...

> "Solutions must be payload-capable, and must not read their source code or use string eval."

> Definition: A quine is payload-capable if it can be extended, in some systematic manner, to include a "payload" of additional code capable of performing arbitrary computation, in addition to printing its source code. A payload-capable quine, in its base form, must include all the code necessary to carry and execute a payload, even if no actual payload is present.

Pavel

Notice how that has half the upvotes of the other one?

Riker

what other one

oh, i see it now

also, that's a really bad definition (the encoding one) as it stands IMO

what's "encode"

"One can easily identify parts of the string which encode bits of the code that are outside the string"

Pavel

Listen, if you want to change it, feel free to answer it yourself.

Riker

@ATaco where is it valid btw?

I think 1\n is what you mean?

Pavel

RProgN, and no, it's 1\n1

Mistah Figgins

01:30

@Riker hmm, why is String eval forbidden?

ATaco

1\n1 was valid in RProgN because it's not just two literals, each literal is printing the other one.

However, due to payload capable being an outstanding rule in the polls, it's no-longer valid.

Pavel

Payload-Capable has almost half the votes of the other one.

Wheat Wizard

If I have 1 rep and I receive a downvote and an upvote on the same question do I get 6 rep or 4 rep?

Riker

@ATaco ah, ok

@WheatWizard which comes first

applied in order

Wheat Wizard

downvote

Pavel

01:33

Then the downvote is not counted.

Riker

then you get 5, for a total of 6

Wheat Wizard

ok thats what I thought

Riker

@ATaco why is the second one explicitly printing the first?

I'd say they're each printing themselves

but I do'nt know much about rprogn

ATaco

1\n2prints 2\n1

Because the implicit printing is backwards, because that's how I wrote it.

Riker

ah, I see

ATaco

01:35

In similar languages, like GolfScript, 1\n2 would print 12\n

Riker

ye

that makes sense in rprogn yah

and to some extent, it is payload capable

ATaco

GolfScript RProgN

Riker

you can add most strings int he middle, right?

ATaco

Not particularly.

Riker

like 1\n"potatoplshere"\n1\n

right?

or do strings not work

ATaco

01:36

That would print 1\npotatoplshere\n1

Strings aren't implicitly escaped, but numbers are fine.

1\n12\n1 would work.

Riker

hm, I see what you mean

hm, you can put an arbitrary string it if you enclose it in {}

ATaco

In RProgN2, yes.

I did a few things with 2 that was an attempt to break our current quine definitions.

Pavel

RProgN is weird

ATaco

The q function returns the the current running function, for instance.

Riker

o_O like?

ATaco

01:39

RProgN2 doesn't care for your multi-digit decimals.

Riker

??

ah I see

ATaco

RProgN2 considers each digit separately, the . thus combined the 1 and the 0.

Riker

ah

ATaco

You can use $0.2, but that's obviously not a quine.

RProgN2 is very weird

Pavel

But... why?

ATaco

01:42

The resulting string of {} isn't taken from the raw string used to construct it.

It's a best guess from the concept array it was passed.

I should probably document this

Pavel

So, it's an array. Why isn't the array printed with some delimiter between elements?

ATaco

Because a Concept array is just a fancy name for a function.

Pavel

oic

ATaco

The function {]+} is a valid usable function, and I'd like it's string representation to also look like {]+}. But it doesn't particularly matter if it looked like { ] + } or {\n\t]\n\t+\n} either.

Pavel

Yeah, I see.

DJMcMayhem

01:46

@Riker Does it really have to be payload capable? For example, 2i2i is not, but I don't think it's a cheating quine

Riker

it is, sorta

DJMcMayhem

How?

Riker

20 mins ago, by Riker

<somethinghere>2i<somethinghere>2i

DJMcMayhem

Oh, I didn't see you guys had already discussed that example

Pavel

Yeah, why don't you consider 2i2i extensible?

Riker

01:47

?

I do?

DJMcMayhem

Because it isn't really? I mean, you can add stuff before it, but you could always add a quine before something non-quiney

@Riker (I think he meant me)

ATaco

q was my attempt to prove the possibility of a 1 byte quine, because it's uniquely encoded, but it was overruled by the fact that encoding done by the end-of-program doesn't particularly count.

Riker

ah ok

@DJMcMayhem that's the point, you can't always

look at 1\n, in most langauges with implicit output

DJMcMayhem

So something is not a cheating quine as long as you can prepend a quine to it?

Riker

it's not easy (if possible) to add any string to it

@DJMcMayhem vice versa

something is not a cheating quine if you can append any non-quine string/piece of code to the beginning (or end, or middle, or anywhere) and have it still work

ATaco

01:49

The difference here was that q is not just outputting it, but it was also encoding half of the quine.

Riker

i.e. if you can carry a "payload" and embed it in the code, then it's allowed

DJMcMayhem

@Riker But that's not true. If I put i at the beginning of 2i2i, then it does not output the first i

Riker

hm

i<esc>2ii<esc>2i?

hm, that doesn't work

DJMcMayhem

I guess you could do ñéÑ~"qpÿ2A2A which is two quines next to eachother that luckily work

Riker

welp, I'm out for the night

DJMcMayhem

01:52

Can we have the definition of a cheating quine be I know it when I see it?

Pavel

That would be great.

Riker

see y'all tomorrow

DJMcMayhem

Bye

Pavel

o/

@DJMcMayhem wut please explain

Riker

"welp. sorry, tnb. this is why i shouldn't say brb when i might not be back." ~~ ~~sans~~ riker

DJMcMayhem

01:54

@Pavel ñéÑ~"qpÿ --> "Boring quine" 2A --> Two times append: 2A --> The string '2A'

Pavel

Oh, I forgot what A did.

Do numbers work on any operation?

DJMcMayhem

However, the reverse 2i2iñéÑ~"qpÿ most definitely does not work

@Pavel Other than some minor exceptions (that are mostly oversights on my part)

Pavel

So, I don't have a computer with Vim on it right now, but can I do 2:s/./&&/g to quadruple every character? (I might have done that wrong, eh)

DJMcMayhem

Almost!

Instead, that doubles every character on the current line and the next line Try it online!

Would you like a vim solution or a V solution? Because in V you could do 2ñ:s/./&&/g but in vim the shortest would be :s/./&&/g<cr>@:

Pavel

@DJMcMayhem This, more than anything else, demonstrates why I don't, but want to, use Vim.

ATaco

02:01

So far the Shortest Valid RProgN2 quine is "%q]F"]F

Pavel

2BlackMagic4Me

DJMcMayhem

(Although technically in V you would want 2ñÓ./&& instead, it's basically the same thing)

ATaco

But there are a lot of ways to write a quine, like {']C'.}]C

DJMcMayhem

@Pavel Haha, it's not too complicated. @: simply means Repeat last ex-command

You can always ping me with vim questions, I enjoy sharing it with people/teaching about vim

Pavel

If I'm writing a language, how do I make it so that installing it adds a man page?

Conor O'Brien

02:15

@ATaco is it possible to have a hash of classes? E.g., HashTable<String, E> where E is an interface

ATaco

Maybe?

RProgN uses a Hash of initialized classes, not the classes themselves, but it may be possible.

Pavel

@ConorO'Brien That creates a hash of objects that implement E

ATaco

HashMap<String, Class<Callable>> classes = new HashMap<String, Class<Callable>>(); does work.

Conor O'Brien

so, then I could do classes.put("asdf", foo); new classes.get("asfd")();?

Pavel

@ATaco HashMap<String, Class<Callable>> classes = new HashMap<>();

Golfed it for you.

@ConorO'Brien No. You would have to call .run() or whatever the method is called on it.

You can't just put parentheses after it, nothing in Java works like that.

@ConorO'Brien are you trying to store objects or classes you can create objects from?

ATaco

02:20

This doesn't seem to support interfaces though, you'll need to use a class parent.

Conor O'Brien

@Pavel classes I can create objects from

Pavel

@ConorO'Brien Hashmap<String, Class> map = new HashMap<>();

This won't let you validate that the class extends a particular interface at compile time, but you don't need to.

Conor O'Brien

and then, map.put("foo", foo); new map.get("foo")(); ?

Pavel

@ConorO'Brien Not quite.

Class is it's own class that has various methods.

map.get("foo").newInstance();

ATaco

map.keySet("foo", foo.class)

Pavel

02:25

Is class static? I always forget.

@ConorO'Brien Yeah, sorry, I assumed foo was a Class object and not the name of the class >_>

Conor O'Brien

and I can pass init args to newInstance?

@Pavel oh lol

Pavel

@ConorO'Brien No. You have to call getDeclaredConstructor() on it, with the args you need.

Conor O'Brien

do I need any special imports for this?

Pavel

This is the point where you have to look it up in the doc, becuase it gets really complicated.

@ConorO'Brien I think it's java.util.reflect.* but I'm not sure. One second.

Wait no

It's part of java.lang

docs.oracle.com/javase/8/docs/api/java/lang/Class.html

@ConorO'Brien map.get("foo").getDeclaredConstructor(Integer.class).newInstance(4);

Conor O'Brien

o_o what does 4 do

Pavel

02:29

It's an example.

Conor O'Brien

like, for args?

Pavel

I'm assuming that the constructor takes an int as a paramter.

Conor O'Brien

ah

Pavel

That's also what the Integer.class is for.

And then you get an object of type Object, remember to cast it to the necessary interface.

Mistah Figgins

@Pavel and collections of Integers

e.g. ArrayList<Integer>

Pavel

02:31

@MistahFiggins That, my friend, is where it gets incredibly terrifying.

I have no goddamned clue.

Mistah Figgins

about?

Pavel

How to tell it that it expects an arraylist of integers.

ArrayList<Integer>.class is an error.

I just tried it.

Reflection and Diamonds seem to just give up and die on each other.

Mistah Figgins

I assume Internally, it's a collection of Objects, and there is a wrapping mechanism that casts to object when adding, and to whatever is in the <...>s when reading from it.

@Pavel But that is weird

Pavel

@MistahFiggins Not really, the diamond is only used in declaration.

Wait, I have an idea.

Wait, I'll test another idea first.

I may have forgotten to import arraylists.

No it's still an error

Yeah, I got nothing.

You can't seem to extract a Class object with diamonds.

ATaco

I'm a bit worried about why you need to store an array of Class's.

Pavel

02:39

@ATaco There is that, we spent so long trying to figure this out that we missed the underlying problem.

Mistah Figgins

Doing new ArrayList<Integer>().getClass() works

ATaco

The X-Y problem is a train with no breaks for Java.

Pavel

@MistahFiggins You mean it doesn't error. As far as I can tell, the resulting Class object has no knowledge of what was in the Diamond originally, and just gives the generic ArrayList class.

Mistah Figgins

But it doesn't give you Integer

@Pavel Yeah, it gives you ArrayList

Pavel

Exactly, so unless your constructor need an arbitrary arraylist as a parameter...

Fun fact. 4+' ' gives 36, but as an Integer object, not an int.

ASCII-only

02:42

this doesn't help?

Pavel

It probably does, but I always forget what the things are called.

ATaco

The Integer object is just a wrapper for int.

Pavel

I just call them diamonds.

@ATaco I know, but just 4 gives an int.

ATaco

I both love and hate that Integer exists.

Pavel

I understand the reasoning behind it, but I still wish you could put ints in an ArrayList.

@MistahFiggins tl;dr, don't store Class objects, store strings, and use a switch-case.

ATaco

02:46

Better, store the objects themselves, and don't use a switch-case.

Mistah Figgins

@Pavel Enums?

Pavel

Right, forgot about those.

Yeah, use Enums

The point is, don't store Class objects.

Ever.

It does not end well.

ATaco

Most efficient

ASCII-only

ew

why not store class objects

Pavel

@ATaco See, now that there is godawful

@ASCII-only Because java Reflection is terrible.

Mistah Figgins

02:48

@ATaco /r/shittyprogramming?

Pavel

There is always a better way

@MistahFiggins No, that's RProgN2's code.

ATaco

Rude. That's my shitty programming you're talking about.

ASCII-only

@Pavel How?

Mistah Figgins

Hey, we all have at least a class's worth

ASCII-only

Use the SO post I linked, then class.getConstructor().newInstance(params)?

Pavel

02:50

@ASCII-only It's a bit uglier than that in actuallity, but in essense yes. But the point is, there's always a better way.

Mistah Figgins

I looked back on one of my year old projects, for about 5 seconds before I noped out of there. It's like I accidentally balanced a bunch of toothpicks with code, and If I touch it, it will all break

Pavel

Like enums

ASCII-only

Enums are just a pain

Pavel

I know

Reflection is more so

ASCII-only

how

use reflection to get the object -> you're done! no more reflection!

Mistah Figgins

02:51

Enums aren't so bad...

Maybe for that instance they are though

ASCII-only

Yeah, enums are useful a lot of the time but definitely not here

Pavel

@ASCII-only Generics are pain tho.

ATaco

It depends how flexible you want your language, and other things.

Pavel

Ok, it's really nice that we have the Reflection API at all, and there are certainly use-cases for it, but in general it should probably be avoided.

Conor O'Brien

@Pavel could I also use a hashtable?

ASCII-only

02:53

@Pavel no generics are the best

Conor O'Brien

also, ^

Pavel

Generics are nice. Generics+Reflection are pain.

ASCII-only

as long as you don't need to nest them like >4 times

Pavel

@ConorO'Brien Probably, I don't honestly know the difference.

Conor O'Brien

ok

Pavel

02:54

I just remember that Hashmaps are the fastest in 90% of cases.

user2284570

@Riker this should be common knowledge as long as you known what android or Linux is. But ok, It’s done.

Can it be reopened now ?

Conor O'Brien

what if I'm a windows user (like I am)

Pavel

Or a noob (like I am)

(I know what an ELF is, but no idea how it's structured and such)

ATaco

@user2284570 Maybe you shouldn't be concentrating on this particular question.

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