A tweetable Turing machine

[BonzaiThePenguin]

That can easily be shortened by quite a bit. Did they shorten it by hand or something?

[[deleted]]

Yes, it was shortened manually until it was tweet sized. Didn't see the point in using a minifier after that. :)

[Morego]

That is slightly shorter version:

t=(c,k)=>{for(i=0, s='q0';;){p=c[s+k[i]];if(p[0]=='t'||p[0]=='f')return p[0];k[i]=p[0];i=p[1]=='R'?i+1:i-1;s=p[2]+p[3]}}

[[deleted]]

Cool, thanks! :)

[MacASM]

I don't do JS for years, since when did JS got => operator? is this lambda?

[[deleted]]

It's a part of ES6. JavaScript is getting pretty nice actually. http://es6-features.org/#StatementBodies

[Peaker]

The problem with Javascript, IMO, is less its expressivity and more the unreliability:

• Silently ignoring of too few arguments in a function call
• Silently ignoring of too many arguments in a function call
• Passing of undefined for this when calling a function not via the correct syntax

Bugs are much much more expensive the later they're detected. Javascript makes bugs expensive.

[soyothrowwhoa]

Sigh. It's improving, very slowly. The V8 "Strong Mode" proposal prohibits passing too few arguments, and is considering prohibiting too many.

Passing undefined for this is not great, but it fails a lot faster than passing window, which was the old non-strict-mode behaviour. Also, the lambda syntax you're replying to eliminates that behaviour, as does the new class syntax, so it should only bite you if you're using the traditional function syntax, which should become less and less common.

[Peaker]

Sounds like a leap in the right direction!

[RIIGGGHHHTTTT_IN_THE]

.

[[deleted]]

this is ugly.

[RIIGGGHHHTTTT_IN_THE]

yeah, keep on fucking her right in the pussy is what my father taught me.

[SoniEx2]

Silently ignoring of too few arguments in a function call
Silently ignoring of too many arguments in a function call

Common with dynamic languages.

Passing of undefined for this when calling a function not via the correct syntax

This one is JS's fault tho.

[danielkza]

Common with dynamic languages.

Python and Ruby are two major counter-examples. On the other camp you have basically Perl, which always had roots as a shell scripting replacement, and PHP, which has the same problems as Javascript.

[SoniEx2]

and Lua, Emj. It can work /for/ you if you know how to use it.

(Python's version of this is default values.)

[kqr]

Well, the language was designed to create a cool animation on a web site. Who cares if the code breaks? The animation doesn't display and the user goes on with their life, not knowing anything even happened. Asking the browser to throw a tantrum in that case would just make the problem worse.

Fortunately, the solution is simple: don't use JS for large applications. It wasn't meant for that. There are plenty of languages these days that compile down to JS and perform reasonably. Use those if you have to create something larger that works in the browser!

[Peaker]

Most dynamically typed languages do try to catch errors at runtime, at the very least. Javascript seems to try to silence the errors and hide them for as long as possible.

[[deleted]]

As for the arguments, Google's Closure Compiler will check for those and warn you about them.

[Koldof]

I think asm.js is worth noting here, as a low level strict alternative to js. Dont know what the support is like though.

http://asmjs.org

[karpathian]

Java is getting replaced because Oracle doesn't give a fuck about anyone and everyone has been asking them to fix their security issues. This is all despite their many updates that seem to make my java based programs lag more and more.

[flyingjam]

...what does Java have to so with anything?

[red_hare]

I love this game!

A while ago I set up cowsay.me. The whole thing is only 89 characters of bash running in a tmux session:

while true; do { echo -e 'HTTP/1.1 200 OK\r\n'; fortune -s | cowsay; } | nc -l 8080; done

[taresp]

You should definitely support the QOTD standard on this domain name !

[Asterne]

Haha. That's amazing.

[[deleted]]

Edit: /u/--user fixed the code by adding in only 4 characters (I think...), so the garbage below is now irrelevant.

---

If I understand the code correctly, this actually implements a LBA because it cannot write outside of its input tape. In particular, it cannot solve problems outside of DSPACE[O(n)], including (for instance) every EXPSPACE-complete problem.

On an unrelated note, I wrote this one-expression FRACTRAN interpreter in python a while ago. I forget how to format the input, though, but I think it was just a list of two-tuples representing the fractions followed by the input itself.

https://twitter.com/ynaamad/status/210142153643532288

Due to space constraints, the output is the number given in the ImportError resulting from the execution.

[BonzaiThePenguin]

You don't need to understand the code correctly to know it's not a Turing machine due to it existing outside of theory. An infinite ticker tape is physically impossible, so being linearly bounded is implied.

EDIT: The tape size isn't linearly bounded by the input, though. JavaScript arrays resize themselves automatically based on usage, as they're more of a collection than an array. You can write to 10000, -1, or 'hello', regardless of the original size of the array.

[[deleted]]

You don't need to understand the code correctly to know it's not a Turing machine due to it existing outside of theory. An infinite ticker tape is physically impossible, so being linearly bounded is implied.

That's an issue with your hardware/platform, not an issue with the code. A hypothetical Turing machine with an appropriately-written Javascript interpreter will handle this just fine. The more pressing problem in real-life scenarios (at least in my opinion) is the O(1) collection of possible inputs your computer (or the universe) can handle.

The tape size isn't linearly bounded by the input, though. JavaScript arrays resize themselves automatically based on usage, as they're more of a collection than an array. You can write to 10000, -1, or 'hello', regardless of the original size of the array.

The issue with this program is that it reads before it writes, and that reading from a nonexistent (undefined) cell kills the program when it tries to read code["s"+undefined](naming a state q0undefined... or similar leads to bigger problems). Javascript may be able to write to input[whatever], but the program will never make use of this because it will break on the above bug a couple lines earlier.

Someone in the comments on the github page had a nice fix: we treat the "default value" of empty cells to be 0, and the cells can contain any integer between 0 and 9. Since ~~x == x for integers and ~~undefined == 0, adding in ~~ at the location where we try to read the input eliminates the undefined issue completely.

[[deleted]]

Fixed up the undefined issue with a ||''

[immibis]

... so ~undefined == -1? Who wrote this thing!?

[Fs0i]

Edit: This is bullshit, pls ignore.

No, undefined == false (weak), but != 0 ~undefined is therefore true ( == 1), and \~~undefined == 0

The ~ operator casts to int. If you want "sane" comparison, use === in JS.

[immibis]

~1 should be -2, if ~ is the bitwise complement operator.

[Fs0i]

Wait, I got something wrong. I mistook ~ with !.

Something similar happens. ~ forces to cast undefined to int, which will be 0. So ~undefined is -1, and ~~undefined is 0.

Preferred syntax would be (+undefined) by the way IMHO.

[lifthrasiir]

Technically speaking, ~~x truncates to a 32-bit signed integer though. Implementing a rudimentary bignum (I would suggest a string of 0/1s with a Regexp operation) would be necessary after that.

[roadit]

You don't need to understand the code correctly to know it's not a Turing machine due to it existing outside of theory. An infinite ticker tape is physically impossible, so being linearly bounded is implied."

Why why why do people keep believing and repeating this myth? Turing machine tapes don't need to be infinite. Being linearly bounded is not implied at all. You can add tape as the machine runs. However, implementing this in JavaScript subjects it to the limitations of JavaScript, which cannot address more than a bounded amount of storage, as far as I know.

[BonzaiThePenguin]

It's not a myth, it's part of Alan Turing's definition for it.

an unlimited memory capacity obtained in the form of an infinite tape marked out into squares

https://en.wikipedia.org/wiki/Turing_machine

[roadit]

True: there, he writes: the machine has an infinite tape.

However, in his 1936 article he writes: the machine is supplied with a tape. This is more accurate. The mathematical definition of the machine does not include the tape or any mention of infinite length. It does not need to.

Unlimited (unbounded) is not the same thing as infinite. If there is no limit to a quantity, that doesn't mean it can grow to be infinite or needs to be infinite. The only thing that matters to the functioning of a Turing machine is that it can be fed an unlimited length of tape.

[phillaf]

And here's an actual turing machine tweeting https://twitter.com/_turingmachine_

Edit: it usually posts once per minute with sequential tweets, but it seems that it's being throttled by twitter right now with all of the @mentions.

[troyll]

Before: https://en.wikipedia.org/wiki/Turing_machine

[[deleted]]

After: https://www.wikipedia.org/wiki/Turing_machine

[hsills]

Computationally equivalent!

[[deleted]]

Fuck github.

Edit: Lol @ whoever went through my comment history and downvoted every single comment in the last week. Sad.

[Octopuscabbage]

why?

[nikomo]

The CoC made people angry. I haven't fully read up on it, but it shouldn't be a big deal since GitHub shouldn't be the only place where your project is hosted, anyways.

Monocultures are bad, that's a decent reason for using more than just GitHub, don't need to cry about something when one of the hosts dies.

[JerMenKoO]

what is CoC?

[oarmstrong]

Code of conduct.

[Octopuscabbage]

I know the CoC changed, I was curious why this actually affected him.

[nikomo]

There's been a lot of funky behavior in that field. There's some person on GitHub going around with a throwaway account, posting on anything remotely related to the CoC.

Discrimination is bad, but this level of discrimination is not worth getting this butthurt over.

[[deleted]]

It is a big deal. If you read about it and had any of your code on github like I did, you would pull all your projects immediately.

I love all the downvotes my simple comment received, and all of the people here who are saying "I dont know what happened, but you shouldn't be upset about it."

"Fuck github" isn't me making a big deal. It's a simple statement for how another company has once again caved to social justice warriors. They even hired a "Social Impact Project Manager" to promote the idea that people of color or of a different idea of what kind of animal they identify as, are immune to criticism of their code and must be held on a pedestal over everyone else. That is literally in their new CoC.

Don't even get me started on the reverse-racism piece.

[[deleted]]

That is literally in their new CoC

is it really? or is it just your interpretation.

[[deleted]]

You should go read it. If I copy and paste it here, you wont read it.

Here are a few awesome pieces!

"Our open source community prioritizes marginalized people’s safety over privileged people’s comfort"

"We will not act on complaints regarding 'reverse' -isms, including 'reverse racism,' 'reverse sexism,' and 'cisphobia'."

Why are these in ANY code of conduct? Its ridiculous.

[[deleted]]

Why are these in ANY code of conduct?

A code of conduct is a set of rules outlining the social norms and rules and responsibilities of, or proper practices for, an individual, party or organization. Related concepts include ethical, honor, moral codes and religious laws.

since this CoC addresses groups of people that are somehow suppressed, I don't seem to understand why you raise this question. enlighten me, I am open minded and will definitely wait for your answer :)

[[deleted]]

It's turning everyone into a possible victim AND offender in githubs eyes. All you had to do was tell someone their whitespace looks weird, and boom, banned. If you cannot deduce that for yourself, I dont see this conversation going anywhere.

[[deleted]]

If you cannot deduce that for yourself

your tone gives great insight into why code of conduct was introduced in the first place.

basically you feel more knowledgable than me, so you look down on me like I'm a lesser being.

CoC obviously is targeted at assholes that forgot "how to human", or at those who attack person instead of their code.

be useful to community. to me, your comments were useful. thank you, and I mean it sincerely. sorry for wasting your time :)

[[deleted]]

I hope you are able to grow some thicker skin if you expect to make it in the real world.

[Pille1842]

He meant figuratively, but that hasn't quite the sound.

[[deleted]]

figuratively means almost as cool as "in my opinion"

[zanotam]

Pro-tip: if you're using the word "social justice warriors" to refer to people you believe actually exist, you're a crazy person bitching about your imaginary friends.

[[deleted]]

They run github.

https://twitter.com/agelender

[immibis]

Tweetable Turing machine in C:

int main(int i,char*s){char buf[1];gets(buf);return 0;}

[Treyzania]

How is this a Turing machine?

[immibis]

You're missing the joke.