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A Stack of Pushdown Automata Variations
Pushdown Automata (PA) tend to get overlooked in the computer theory course, with only the basic model being explained. Here we take a dive into the surprisingly diverse array of variations that have been produced over the years, and what they mean for the field as a whole. The major sections will be the automata basics, why the PA is kind of weird, stack automata, alternating automata, and visibly pushdown automata. You shouldn't need any knowledge before going in, as we explain complexity classes, closures and decision problems too!
Join our Discord for the Q&A after the talk: discord.gg/n6chXAZ
hacksoc.org
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มุมมอง: 82

วีดีโอ

The History of Calculators - Aaron Christiansen
มุมมอง 2.2K2 ปีที่แล้ว
Ever since picking up my first scientific Casio for GCSEs, I've had a strange fascination with calculators. Even in today's smartphone-dominated world, these single-purpose devices still hold an important place, especially in education. As one of the earliest forms of a crude pocket computer, they also have a rich history - which I'll cover in this talk! From the earliest mechanical models, to ...
What actually is an Operating System? - Jacob Allen
มุมมอง 1502 ปีที่แล้ว
Operating Systems are everywhere. At the core of most computers, be they desktops or embedded systems, an Operating System is running. However, there are a wide gamut of different things we call an Operating System. What, then, makes an Operating System what it is? Why do we even need Operating Systems in the first place? In this talk I will explain the origins of Operating Systems and what the...
RISC-V, and why it isn't as risky as you think - Daniel Allinson
มุมมอง 1882 ปีที่แล้ว
RISC-V is a new instruction set architecture created for use in many different types of CPU core. But what exactly is it? How does it work? How does it compare to the instruction set used in our modern computers? Join our Discord for the Q&A after the talk: discord.gg/n6chXAZ hacksoc.org hacksoc groups/hacksoc hacksoc-york.slack.com
A (Very) Brief History of the Technology of String - C Wringe
มุมมอง 1122 ปีที่แล้ว
Textiles have their history in the field of computer science. From the Jacquard Looms that every first year learns was the inspiration for programmable computers, to the fact that we call sequences of characters strings, we can't seem to escape them. (And if you think you can, just wait until that one student brings it up as an example in every. single. seminar. :P) Given this, I posit that it ...
How Robot Swarms Can Help Solve Hard Problems - C Wringe
มุมมอง 1323 ปีที่แล้ว
Some tasks are too difficult for most robots to complete. And yet, insects perform them with apparent ease. Enter the biologically inspired robot swarm: A group of robots, individually performing simple tasks to create a more complex whole. In this talk, I will go over what a robot swarm is, and the sorts of problems they can solve. I will show what it means for a robot swarm to be scalable, fl...
Dispatches from the Computing Titanic - Jacob Allen
มุมมอง 973 ปีที่แล้ว
Contrary to many jokes, computers are (on the whole) well behaved and predictable machines that do exactly what you ask them to. This is why it is so much more noteworthy when they do not do what they were asked to, or worse, do exactly what they were asked to but not what was wanted. No better is this shown in what have come to be known as "cursed" parts of computing, such as those shown in th...
The Revised⁷ Report on the Algorithmic Language Scheme - Daphne Preston-Kendal
มุมมอง 5K3 ปีที่แล้ว
(EDIT 20/08/2023: The current status of the project as outlined in this academic talk is, as of now, outdated) Scheme is a small but influential dialect of the Lisp programming language which has been standardized in multiple more-or-less compatible versions since its creation in the late 1970s. After decades of being used almost exclusively in teaching and research (with some exceptions), Sche...
Talk In Which Matt Talks For 30 Minutes about Sonic the Hedgehog™ - Matt Windsor
มุมมอง 2173 ปีที่แล้ว
Sonic the Hedgehog™ turns 30 this year, as do I. Alas, before 2021 I had never actually properly sat down and played a Sonic game. In fact, I didn't even have a Mega Drive until the mid-10s. Shocking, I know! In this talk, I'll deep dive into how I went from a washed-up Mario fan to a full-on second childhood with the blue blur, with a goal to become a Sonic CD speedrunner some time this millen...
An Introduction To Constraint Programming - Jacob Allen
มุมมอง 16K3 ปีที่แล้ว
As a programmer, computer scientist, computer engineer etc. there are many problems for which an algorithm can easily be determined or pulled from a text book, however, there is a class (or really two classes) of problems for which there are rarely such simple solutions: constraint problems. Luckily there exist powerful constraint programming tools to allow us to solve constraint problems using...
Can Concurrency Testing Be Liberated From The Litmus Style? - Matt Windsor
มุมมอง 953 ปีที่แล้ว
The 'litmus test' is a de facto standard for lightweight tests of concurrent systems, packaging shared state, initial values, expected final values, and thread bodies into a concise and readable format. In this talk, I discuss litmus tests, how they are used in testing, the challenges of using them in compiler fuzz testing, and experimental attempts to overcome those challenges. Join our Discor...
Personal Identity and Fission Cases - Rach Arnold
มุมมอง 2073 ปีที่แล้ว
In this talk, I will be exploring an issue regarding psychological continuity and the persistence question (i.e. how do persons persist through time). I will be discussing why fission cases pose a problem for psychological continuity theories, as it presents itself as a logical contradiction. In order to reconcile this issue, I will be drawing upon the work of Derek Parfit and David Lewis to se...
How To Build and Betray Online Communities: A Ravelry Case Study - C Wringe
มุมมอง 1.7K3 ปีที่แล้ว
Ravelry is a (relatively) small site for knitters and crocheters to share patterns, projects, and discussions. Being the main point for a (relatively) small community, there is some tea. At times, it has performed admirably - at others, failed miserably. This makes it a great case study for those building platforms for online communities: What to adopt, where to improve, and what to never (oh g...
The History of LEGO Video Games - David Norman
มุมมอง 1083 ปีที่แล้ว
Recorded on 24th October 2019 In the past 22 years, LEGO Video Games have become an important and rather unique genre in themselves. In this talk, we will look at how they have changed over time, the different styles and directions that have been attempted, and their cultural impact. hacksoc.org hacksoc groups/hacksoc hacksoc-york.slack.com
The Life And Times Of HTTPS - Marks Polakovs
มุมมอง 1233 ปีที่แล้ว
Fifteen or twenty years ago you'd have been a fool for signing in to your MySpace account on any internet connection except for the one at your home. All your account details were sent unencrypted over the wire, ripe for anyone to steal. Today, however, over 80% of all connections Firefox makes are encrypted, and with every day we get closed and closer to universal encryption. How did we get he...
Lerning To Rite Gud - Abi Sutherland
มุมมอง 1963 ปีที่แล้ว
Lerning To Rite Gud - Abi Sutherland
Mapping with Robots - Jacob Allen
มุมมอง 3433 ปีที่แล้ว
Mapping with Robots - Jacob Allen
The Power of Cursed Code: A Tour of Ruby - Aaron Christiansen
มุมมอง 1894 ปีที่แล้ว
The Power of Cursed Code: A Tour of Ruby - Aaron Christiansen
How alike are Computers and Minds? - Rach Arnold
มุมมอง 654 ปีที่แล้ว
How alike are Computers and Minds? - Rach Arnold
Abstraction and Complexity Management - Jacob Allen
มุมมอง 2134 ปีที่แล้ว
Abstraction and Complexity Management - Jacob Allen
Ebooks are a Hard Problem - C Wringe
มุมมอง 1194 ปีที่แล้ว
Ebooks are a Hard Problem - C Wringe
How to move a radio station online in five weeks or less - Marks Polakovs
มุมมอง 1704 ปีที่แล้ว
How to move a radio station online in five weeks or less - Marks Polakovs
Regular event calendar
มุมมอง 1017 ปีที่แล้ว
Regular event calendar
A Tour of Esoteric Programming Languages
มุมมอง 44110 ปีที่แล้ว
A Tour of Esoteric Programming Languages

ความคิดเห็น

  • @kimchee94112
    @kimchee94112 วันที่ผ่านมา

    Excellent video on the subject getting me up to date. No more slide rules and CRC Handbook look up tables. I pretty much stopped at HP-15c. TI SR-50 was my first couldn't afford the HP-35. I now have a collections of HPs including the 35 and HP 50g. No idea how to use the 50g, getting into the owner's manual later. Too bad RPN going out of favor.

  • @Alex-jb5tb
    @Alex-jb5tb 3 หลายเดือนก่อน

    Great documentary. Thank you !

  • @lmpombo
    @lmpombo 7 หลายเดือนก่อน

    I lost count of the number of calculators I have. There can be computers, spreadsheets, mobile phones and the hell with numbers... I just love calculators in general. Of my favourites I even have multiples, like the HP-15c or the Casio fx-570ms or the TI-89. There is nothing better than a literal physical calculator to crunch numbers! This was an excellent video, thank you for it!

  • @marklgarcia
    @marklgarcia 7 หลายเดือนก่อน

    Not sure how I ended up here, but I found this very interesting. I still use my HP-41CV that is now 40 years old.

  • @Jenseeea
    @Jenseeea 10 หลายเดือนก่อน

    Thank you! Better than my professors

  • @rafaveggi
    @rafaveggi ปีที่แล้ว

    Starts talking about Sonic at 7:45 Good talk, thanks for sharing

  • @the_nuckelavee
    @the_nuckelavee ปีที่แล้ว

    BAD! i cannot listen it calmly -the pronunciation of Daphne Preston-Kendal is just terrible. i have a speech defect myself [i cannot pronounce "l" because i have a mutilation], but i do not pretend on giving any lectures. the subject is just great, she is just not confident or maybe is unprepared to the talk. cannot listen to this syncopation babbling

    • @AdrianColley
      @AdrianColley 10 หลายเดือนก่อน

      You could have expressed your feedback without resorting to insults like "syncopation babbling".

    • @philippeb1507
      @philippeb1507 6 หลายเดือนก่อน

      Funny you feel this way. I’m French, thus English isn’t my mother tongue and I understood every word without difficulty. I guess our individual differences have little to do with the speaker herself.

  • @remya2001
    @remya2001 ปีที่แล้ว

    please replay

  • @remya2001
    @remya2001 ปีที่แล้ว

    with out using robot how to make navigation map in indoor

  • @michaelbauers8800
    @michaelbauers8800 ปีที่แล้ว

    I wasn't sure how we are supposed to subtract with the compometer gizmo, but 10's complement will always work, just like how computers use 2's complement. e.g. 23+76+1=100, ignore the carry. I notice that the calculator has the complements on the digits, e.g. 1 has an 8. This works fine, you enter 23, then enter the complement which is 76, then add 1.

  • @jcfreeify
    @jcfreeify ปีที่แล้ว

    Hi Jacob, once the 7,1,8 & 2 are entered, you say you will guess from there but be prepared to back-track. But what if the 7,1,8,2 configuration itself doesn't allow for any feasible solutions? Don't you have to be ready to backtrack all the way? i.e. there is no set number of initial guesses that you can assume for feasibility.

  • @jasonpepas4290
    @jasonpepas4290 ปีที่แล้ว

    Thanks so much for this!

  • @Michael-oi2sy
    @Michael-oi2sy ปีที่แล้ว

    This video was awesome! I've been getting into Racket and thought I'd see what's going on with R7RS. Did not expect such a good introduction into the history of Scheme.

  • @wangpenghao4322
    @wangpenghao4322 2 ปีที่แล้ว

    Great job explaining these topics!

  • @UFOsandCrochet
    @UFOsandCrochet 2 ปีที่แล้ว

    A lot of people left were not racist and not trump followers. They felt the site should be inclusive as not all trump supporters are racist! I'm a Democrat.

  • @abramswee
    @abramswee 2 ปีที่แล้ว

    thanks for sharing

  • @erikkaplun2355
    @erikkaplun2355 2 ปีที่แล้ว

    CLP(QR) does floating point domains.

  • @ItIsGuf
    @ItIsGuf 2 ปีที่แล้ว

    17:40 How does floating point numbers lead to infinite domains?

    • @fcpereira97
      @fcpereira97 2 ปีที่แล้ว

      Suppose that, in a particular problem, the domain of a certain variable is any rational number between 0 and 1. So, we may want to represent the value of this variable as a floating point number. In that case, we have an infinite numbers between 0 and 1, but constraint programming requires finite domains. I think he meant to say that, in general, if you aim to represent a variable as a floating point number is because you have an infinite domain. However, we might have a problem in which the domains of the variables are all finite, but they contain numbers that are not integers. In that case, we can simply stablish an injective funcion from the union of the domains to the set of integer numbers. In all cases, we avoid floating point numbers. In the first case because we have infinite domains, which is forbidden, and in the second case because we can map the floating point numbers (that belong to finite domains) to integer numbers.

    • @jacoballen4362
      @jacoballen4362 2 ปีที่แล้ว

      ​@@fcpereira97 Indeed you're correct, I meant in the case where we do not have other limits on the domains. As you said there could be any number of values between 0 and 1 even so we cannot have unconstrained rational numbers. But of course, if we can map non-integer values into finite domains we can have non-integer values!

  • @basscass710
    @basscass710 3 ปีที่แล้ว

    Great video i hope after a while guile moves to r7rs but I fucking love guile

  • @suricrasia
    @suricrasia 3 ปีที่แล้ว

    awesome talk! I'm glad my silly little meme inspired you so much :3

  • @zpskk
    @zpskk 3 ปีที่แล้ว

    Even for people that never made any money on rav... some people were so badly affected that they had to take time off work, in some cases very long periods, and/or pay for medical care. 'If you don't have the money to hire an accessibility expert, you don't have the money to redesign.' Darn right!!! If the whole situation weren't so horrible, it would actually be impressive. I've never seen a site cause such an incredible amount of physical harm.

  • @MercuryZelda
    @MercuryZelda 3 ปีที่แล้ว

    I am someone who started using Ravelry in 2009. The redesign gave me a migraine as soon as it rolled out - I was on the website browsing patterns as it changed, and was not seeing any reactions in the forums or the like. What truly irritated me was not the initial accessibility failure - it was the doubling down, refusal to admit anything was wrong, and trying to paint all the harm Ravelry has done as "stress" causing the issues. Their entire response and ignoring users disgusted me, and I delisted my patterns for sale / download on their website. The only functionality I use now is adding my new patterns to the site, but linking to my own shop instead of uploading anything to Ravelry itself. They have shown how little they care.

  • @jenniferknatters3263
    @jenniferknatters3263 3 ปีที่แล้ว

    A point of clarification with the R-team's statement that signups were up 106% over the previous year. You were correct in pointing out that this put them in comparison to the month in 2019 when they included support of the president as support of racism, but after they did that they closed signups for a month so non-knitters who were offended by the ban couldn't create new or puppet accounts and cause a ruckus. So Ravelry was bragging that sign-ups were up compared to a period when they didn't allow signups. That's disingenuous at best.

  • @SarahDawnsDesigns
    @SarahDawnsDesigns 3 ปีที่แล้ว

    Yes, thank you so much for delving into this and really articulating a lot of what happened! It's been a mess for me as a knit/crochet designer (I'm finally able to use NewRav with a custom CSS sheet on top of it, to avoid headaches/nausea/disorientation). I've got a question, if you don't mind? It's a question about something you didn't mention; that I'm curious about: In later social media posts, Ravelry used Twitter (and IG)'s option to remove the ability to comment. I'd be curious to know if this impacted your study at all?

    • @cwringe4025
      @cwringe4025 3 ปีที่แล้ว

      Hi Sarah, I didn't consider hidden replies - I chose twitter because I fail at instagram, and I knew posts had been deleted from the rev forums, but didn't think to see whether the tweets I examined had any hidden replies. I'm not sure how I would have dealt with that, tbh, as my methodology relied on using tweets that had been boosted by the algorithm. On the other hand, having a look at it now, doesn't look like any of the tweets I examined had any hidden replies, by sheer luck. None of the tweets in the time window I chose (which was mostly "what's a time window that captures most of the reactions, while being small enough to analyze for a short talk") turned replies off. If there are other ways the account prevented people from replying, then it's not any I'm aware of, but if you wanted to have a look, the data is all in runciman.hacksoc.org/~uint8_lotte/talks/ravelry/ravelry-data/, I'd be interested to see any other analyses or interpretations.

  • @emmawileman3416
    @emmawileman3416 3 ปีที่แล้ว

    Aside from the awful accessibility issues (the new site gave me a migraine in 15 minutes flat, along with eye strain which lingered for a week, and was certainly not mass hysteria since I had been browsing patterns and so had not seen any forum posts complaining of issues) there are a number of side issues with the new design which also caused anger and disengagement. One, as mentioned above, was the site having a more strongly feminine feel instead of the "gender-neutral" feel they claimed to have aimed at. Another was that the new design was very cutesy and young-feeling, likely to appeal to Gen Z but an odd choice here since the overall user profile skews strongly Gen X/older Millennial - this has alienated a lot of the "old guard" who have been Ravellers since its inception, and feel pushed aside. And also, the new site was designed to work and look good on mobile phones, and "broke" in numerous ways for tablet users - eg vast amounts of whitespace, or click buttons being outside the pop-up box they should be in - many of these bugs have not been fixed months later. Also, they were told about the accessibility issues by at least one beta tester, but went ahead anyway. I still use Ravelry daily with the old skin, but who knows if I'll be able to continue after they retire that skin in March. At least two of my Rav communities have set up Zoom and Discord groups so we can keep in touch if it all goes tits-up next spring - this is the level of community cohesion that Ravelry is squandering.

    • @jenchris40
      @jenchris40 3 ปีที่แล้ว

      Several beta testers reported the bug. And they only employed 100 testers in the first place. The only response I received was to tell me that it works much better on mobile phones now. I don't use my mobile for this stuff because I need a big screen. Popularity over accessibility time after time, hand over fist. I've taken my money elsewhere.

  • @jenchris40
    @jenchris40 3 ปีที่แล้ว

    I'm one of those who are unable to use Ravelry any more. It was a nightmare before. But for the record, it's NOT a voluntary run community - this is a business charging designers to advertise their patterns, and taking a cut from sales. It is absolutely not voluntary. There is a large crossover between Twitter and Ravelry - and NuRav has helped this grow. All people wanted from Ravelry was an acknowledgement of the issues people were experiencing; the chance to roll back (which finally came around some weeks later, but which is due to end soon); and an apology that accessibility, by Ravelry's own admission, was only considered at the end of their programming, and not right at the beginning. Ravelry has instead doubled-down and there has been no sincere apology. Many designers and users have left the community as a result. And hey, the world hasn't ended. But for many crafters, Ravelry was home.

    • @jenchris40
      @jenchris40 3 ปีที่แล้ว

      Also, I lost count of the number of people who offered accessible coding help FOR FREE. Ravelry doubled down and turned down all offers, insisting that "a medical expert" they contacted denied that their website could have possibly caused the health issues.

    • @jenniferknatters3263
      @jenniferknatters3263 3 ปีที่แล้ว

      Point of clarity, "the change to roll back" isn't a true return to the previous iteration, it is just a skin over the new page. Some of the problems people were experiencing were caused by the way the new site loads which the old.rav skin didn't fix.

    • @jenchris40
      @jenchris40 3 ปีที่แล้ว

      @@jenniferknatters3263 Thanks for the clarification. I'm not very techy; but I'm not surprised by this. I had continuing problems after I tried the "roll back" button that I couldn't understand. Things just didn't go back to the old version (which, let's face it, was far from perfect from an accessibility angle). Your explanation makes a lot of sense. I gave up on it when they closed the forums and it became extremely clear that their notion of "inclusivity" didn't include disablity.

    • @knit1purl1
      @knit1purl1 3 ปีที่แล้ว

      That site does as they wish. Many people state it's a pattern database ignoring the fact that it sells, advertises and garners revenue. I'm on there but only for free. If I buy a online pattern, it will not be from their site. They seem to listen to no one but themselves.

    • @momofpeg
      @momofpeg 3 ปีที่แล้ว

      The volunteers are the moderators who run the groups for free

  • @alicemerray
    @alicemerray 3 ปีที่แล้ว

    Interesting talk, which I watched as an interested knitter rather than a coder. From my own POV I think the mass hysteria charge is despicable (& agree with you about its inherent misogyny) and also untrue. I was turning the brightness down on "Nu Rav" long before I even saw any accusations of accessibility issues from others, when I thought I was just in the group that thought the whole thing horribly twee but would basically have to put up with it! I'm just lucky that a headache was the worst outcome for me. The other point that I think has contributed to the feelings of betrayal is linked to this idea of Ravelry as "free". Many of us have made donations over the years and there's also a fee if you want to upload pics other than on project pages. But the main thing is that Ravelry has, since its inception, made huge use of volunteers to overcome the problem of having basically one person doing all the coding - Cassidy. Volunteers sorted all the patterns into categories for example, there are loads of volunteer editors and volunteers also moderate most of the forums. Members have worked hard to build the site and saved the founders lots of money in the process. This has, I believe, left people far more invested in the site than in many - most? - others. There also definitely were several accessibility experts (self described, but apparently genuine) offering their services to help correct the problems and all seemingly ignored. It didn't help that the person hired to make the site's appearance over did not appear to be either an accessibility expert or even a knitter, which given a pool of very artistic people at their fingertips feels again like a rejection by Ravelry of the community. Ravelry is not going to disappear any time soon, but they have lost an awful amount of goodwill. Where in recent times potential competition has struggled, there's now a fertile ground for someone. Many designers are looking for other places to sell patterns - which is probably positive, as having all their eggs in one basket clearly was a mistake. But every time a You Tube video maker says "I haven't linked to Ravelry" it feels so sad. It was all so unnecessary.

  • @nancydegener9438
    @nancydegener9438 3 ปีที่แล้ว

    Nice overview. And yes, a great case study of what NOT to do. A couple small corrections, however. Rav isn't a volunteer-run site, The folks running it make a living doing so. Also, there's not a dev team of 6. One full-time dev, 1 part-time dev. The others on staff are in the operations/community aspects of things. Unfortunately, an analysis based off Twitter is a small and skewed sampling as there's little crossover between Rav and Twitter. Some things that factored into a majority-negative response were 1. no warning whatsoever, new site just appeared between page navigation/refreshes, and 2. people already in a state of anxiety due to first few months of pandemic, thus not a good time to drastically change many people's safe/happy space. Based on the main board forum posts, maybe 20-30% were giving new look a thumbs up for seeming fresher/cleaner. Majority, even before the accessibility issues erupted, were disappointed in the twee/juvenile new design and puzzled that anyone thought it was more gender-neutral than original Rav (which was apparently one of the goals). But thank you for keeping this discussion going. I suspect the Rav implosion will be a case study for a while.

    • @momofpeg
      @momofpeg 3 ปีที่แล้ว

      As someone who has been a moderator in groups for years, the groups are volunteer run. We do not get paid for the hours of making sure the groups run smoothly