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3 points by hjek 11 days ago | link | parent | on: Show Arc: Debate (very alpha)

> I've only had to time to take quick look, but I'm impressed at how clean the code looks.

Good to know that it's somewhat readable for people who are not me!

> I could be wrong, but it actually looks smaller in size than Arc's version, but with more features.

It's still smaller and it does have file upload, but there's a lot of news.arc features missing before this one is usable.

> > not a general purpose cms (link to 'The CMS Trap')

> That's me. I'm that guy - lol (well not quite but close).

I read a blog post[0] about Wagtail, a Python CMS, and wanted to try it out. Once up and running, it has a user login/registration form, but you literally can't post anything, because it's more like a CMS framework or something (or maybe that is what CMS really means?). To me that embodied 'The CMS trap'.

> Between, no JS, Free Software and the above I'm getting that you and I have very different goals :)

Yea, good to hear different opinions here.

Ok, so I'm not totally against JS, and I'm using it myself for other stuff. I think I'm just really pro progressive enhancement, and it's sometimes the first thing to go. For example, I don't think HN has a reason to not allow voting w/o JS. I think there's a bit of a tendency to use way too large and slow JS frameworks, but I'm interested in ClojureScript now because it seems to be all about eliminating dead code and optimizing.

[0] https://torchbox.com/blog/torchbox-has-dropped-drupal/

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3 points by i4cu 10 days ago | link

> I read a blog post[0] about Wagtail,....because it's more like a CMS framework...

Yeah neither Drupal nor Wagtail sound remotely appealing to me. A CMS, in general terms, is just that: a Content Management System. Now that's pretty broad with lots of room for products which are both good and bad.

Personally I'm interested in the Business Intelligence space where people build Apps, only I'm targeting companies who wish to empower their Business Analysts (or specifically the blue to 'purple people') to build apps and streamline inefficient IT processes.

I'm not sure if BI apps are considered a CMS or not, but when I read that 'trap' article I couldn't help but relate.

> I think I'm just really pro progressive enhancement, and it's sometimes the first thing to go.

Well progressive enhancement is not, not using JS.

Progressive Enhancement is pretty much the opposite of Graceful Degradation. In GD you fallback to allow lesser technologies to handle the workload, where PE is starting with limited functionality and build up incrementally to gracefully handle the workload. JS is often what is used to achieve PE.

> I think there's a bit of a tendency to use way too large and slow JS frameworks, but I'm interested in ClojureScript now because it seems to be all about eliminating dead code and optimizing.

Yep.

All I can say here is that automation and the benefits that comes from that will have a cost. Your product/app/page will contain larger files which do some amount of work for you.

Developers have a tendency to see 'frameworks' from a maximal code efficiency perspective, but frameworks really are all about lessening the $ cost, the work burden, time to market and the operational maintenance. The argument is always "If you're building a blog you shouldn't need a framework." And that's true, but most frameworks are not built for making blogs, they're built for greater things - however if said framework makes it easier for person A to do thing X, even if it's just a blog then, really, it's hard not to see it happening (even though developers don't like to see it).

Frameworks, really, are for when large tailor made products become nightmares to manage, that's when they become the go to "solution" and start to shine. Modern day web development has a lot of pitfalls and will require a skillset that not everyone has. Not everyone can make dynamic apps that don't get bogged down by limiting factors like the DOM tree (cluster fuck), rendering/paint (bottle-necks), and single threaded environments (the async data gotcha's). Frameworks can help with all this, but it's at a cost. The file size is bigger, it's not Free Software, it uses JS and you have the potential to be caught-up in a CMS trap.

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3 points by hjek 7 days ago | link

> Well progressive enhancement is not, not using JS. Progressive Enhancement is pretty much the opposite of Graceful Degradation.

Yea, exactly. I'm OK with JavaScript being used for better UX as long as core functionality works w/o JS. From W3C:

> So, graceful degradation is the practice of building your web functionality so that it provides a certain level of user experience in more modern browsers, but it will also degrade gracefully to a lower level of user in experience in older browsers. This lower level is not as nice to use for your site visitors, but it does still provide them with the basic functionality that they came to your site to use; things do not break for them.[0]

If it is assumed that voting is part of the basic functionality of HN, then HN does PE wrong by breaking it when there's no JS. It's a relatively recent change to HN and Anarki doesn't suffer from that issue.

Yet it's neat that HN uses JS to prevent page reloading on voting. I'm just doing no JS at all on my own project here to make sure I don't accidentally rely on it, because I don't really trust myself to use it in moderation.

> Frameworks can help with all this, but it's at a cost. The file size is bigger,

Yea, they're beneficial, but heavy. HN front page: 62K. HN search: 1.19M. Did they really need Angular for that search input form? That's where ClojureScript looks promising though: Their `helloworld` example is just 20K.[1]

[0]: https://www.w3.org/wiki/Graceful_degradation_versus_progress...

[1]: https://clojurescript.org/guides/quick-start

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3 points by i4cu 7 days ago | link

Obviously you're more into graceful degradation than progressive enhancement.

My idea of graceful degradation is falling back to a message that says "sorry, not going to happen!" :)

So, obviously, I'm more into progressive enhancement than graceful degradation.

> ClojureScript looks promising though...

Well to be fair, ClojureScript is not a full fledged framework; It is a framework, but really it's more of a compiler with some library functions. Reagent [1], for example, is a library that bridges the gap between ClojureScript and React. So I'm not sure it's fair to compare ClojureScript to these full fledged frameworks... you're still correct though, in that ClojureScript alone can produce apps with a smaller footprint.

That said & just to compare, last time I checked, React and Elm are appx. 42-45kb, Angular is 90kb. So HN search, obviously need to add their own code to bring it in at 1.19M.

My app, written in pure Clojurescript, is currently at 90kb minified. I hope to bring that down, but chances are the first release will actually be a little larger.

1. https://reagent-project.github.io/

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2 points by hjek 6 days ago | link

> My idea of graceful degradation is falling back to a message that says "sorry, not going to happen!" :)

Hilarious! A degradation for sure but the graceful part of is questionable.

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3 points by hjek 11 days ago | link | parent | on: Show Arc: Debate (very alpha)

> What parts/features do you want to take from each, and why do you think they should coexist in a single product?

DropBox/WeTransfer/Google Drive/OneDrive is just what people use to send larger files. I'm not a fan of those sites, but I have observed that people I know find Filezilla and FTP very intimidating. There's some other free apps for this, but either they're in PHP or they're too complicated to install or use or hack on. Droopy[0] works good for this, so as a start I just cloned what Droopy does; just to check whether Racket/SQLite is fast enough for this use case. (It is)

I like RSS as an idea and the fact that most sites have RSS feeds, but I think it's underappreciated by non-techies, who think that Facebook or Twitter are the only place you can "follow" stuff. For friends of mine to even consider using RSS for anything, I think it needs to be more accessible. I use Newsbeuter for reading RSS but I would never recommend it to non-techie friends, and it has some annoying bugs: Sometimes text is missing, podcast download is flaky at best so I have to copy the url out at get it with curl, and the interface becomes unresponsive when there's many feed items. So I'm thinking of giving it a try to make a web-based RSS reader that encourages sharing and that at very least I'd enjoy using myself. I think this would fit naturally with a News-style app, basically just having RSS feed items being shown alongside other people's posts, but perhaps tweaking the ranking in a way that external feeds don't overshadow local content (assuming that external feed items are votable). Some non-techies have shown me the Feedly app, which (I think) uses RSS, and (I presume) has some kind of social recommendation system, so I just think it would be nice with a free/libre web app doing something similar.

Then, the HN/Lobsters part is basically about having a minimalist web forum with tree structure replies and well thought out ranking algorithms and spam handling, instead of this thoughtless phpBB-style newest-first unstructured mess. One thing Lobsters does right here is that it notifies you when someone replies to a comment of yours. On HN it's possible for someone to reply and you just won't notice because it's so deeply buried in old threads. But I like all the different ways you can sort/view the content on HN.

Also, I've had some painful episodes trying to back up Wordpress sites. It's not pleasant, because there's little distinction between code and content which is stored in a mish-mash of database entries and folders. WP barfs all over the disk. That's something HN does right, because all the content is in the `www` folder. But, then file upload to HN is not really a realistic thing.

So I'm just trying to mix-and-match things I like from different software. A lot of ideas. Haven't gotten far yet! But I guess it's ok to share work-in-progress here.

If I didn't have dockerphobia and mild JS-intolerance, I'd probably just be running Mastodon or something.

[0]: https://github.com/stackp/Droopy/issues?q=is%3Aissue+is%3Acl...

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2 points by akkartik 11 days ago | link

I'm wondering:

1. Are you trying to build an RSS reader? Or do you want to support RSS versions of pages on your site?

2. Are you building a file transfer service? Or are you imagining that people will want to share files on a HN-like website? I'm not sure why that would be a common use case.

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2 points by hjek 11 days ago | link

> 2. Are you building a file transfer service? Or are you imagining that people will want to share files on a HN-like website? I'm not sure why that would be a common use case.

File upload wouldn't make sense on HN, Arc Forum or Lobsters, and I get that it's entirely on purpose that it's not present on those sites.

But I've been hosting a News site, and those of my friends who use it often submit links to something they've put on Dropbox or Google Drive, so I'm simply observing that this use case is present and that file upload is missing on my site. Perhaps it's because it's a different type of exchanges: a guitarist uploading a recording of a Charlie Parker solo, an artist uploading a drawing, etc.

Well, perhaps I should be using $CRAPPY_PHP_CMS_WITH_FILE_UPLOAD instead of News, but why can't I have well-structured content and file uploads at the same time?

It's also about future extensibility, ways of presenting these file uploads that I haven't thought about yet. I do occasionally write PHP for money. I don't have a very high opinion of that language, and I'd rather make something from scratch in Racket than write it as a Drupal plugin. Given the relative quantities of Drupal plugins and Racket web apps, that might be an unpopular opinion, but it shouldn't seem too strange on this forum. I'd prefer to make custom interactive web sites by extending a code base in Racket rather than PHP.

It's actually also for the use-case of being off-the-grid, yet needing to send/receive files to people in the same room, but not being able to find a USB stick. That situation happens surprisingly often for me. A zero-config web app is useful here because everyone have a browser on their computer (whereas not everyone have FTP / SSH / SMB).

> 1. Are you trying to build an RSS reader? Or do you want to support RSS versions of pages on your site?

I plan to do both. Building a social RSS reader integrated in a News-like app. And this News-like app would provide RSS feeds in the same way Anarki does. I image it wouldn't be too difficult.

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I'm somewhat disoriented by the very first example[0]. How is a newcomer meant to grok how this program prints out 42?

    bb/copy-to-EBX  2a/imm32
    # exit(EBX)
    b8/copy-to-EAX  1/imm32
    cd/syscall 0x80/imm8
This is not meant to criticize, but just as feedback from a real assembly newcomer, since this is in your project description:

> It would make it easier to write programs that can be easily understood by newcomers.

[0]: https://github.com/akkartik/mu/blob/master/subx/examples/ex1...

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2 points by akkartik 11 days ago | link

Absolutely valid criticism. I'd love to hear more about what you did between seeing the link here and navigating to that example program. I've been trying to build a path to gradually take programmers to an understanding of (this particular unconventional style of) assembly programming. For example, I'm curious how much of the Readme you read, and if you happened to notice that the Readme has an orientation on the x86 processor.

I also made a couple of tweaks to this particular example. I hadn't looked at it in a while. Thank you! https://github.com/akkartik/mu/commit/d6535f3382

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2 points by hjek 11 days ago | link

I read the first section of the readme without really understanding much but also not expecting to as I don't know x86 assembly. Then I decided to at least give the examples a superficial look as I'd noticed the word newcomers in the readme. But I couldn't see the number `42` in a program meant to print `42`, so that's where I gave up.

Is this meant to be a tutorial for assembly noobs?

For comparison I think your readme for Wart[0] is more welcoming: Briefly explaining what it is and how to run it, and then straight onto a simple example that people can actually try out.

[0]: https://github.com/akkartik/wart

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2 points by akkartik 11 days ago | link

That's a good point. I have similar instructions here, but they're in the second section, 3 screens down..

The audience is assembly-curious programmers, but you aren't expected to know any assembly. I just want to try to hook anyone interested in the goal. If you're interested in a stack you can understand from the ground up, I'm willing to try to explain things to you.

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2 points by hjek 11 days ago | link

I might just be outside the target audience, for now. I don't even know any C. Realistically, I think it would have to be spoon-fed to me in some Bret Victor-esque crocodiles and eggs[0] manner for me to not lose focus.

I went through this absolutely fantastic SQL tutorial this week. Perhaps you might find their list of pedagogical principles[1] useful?

I think one thing that potentially could tempt me into low-level code would be making cool tunes[2][3].

[0]: http://worrydream.com/AlligatorEggs/

[1]: https://selectstarsql.com/frontmatter.html

[2]: https://www.youtube.com/watch?v=GtQdIYUtAHg

[3]: https://www.youtube.com/watch?v=qlrs2Vorw2Y

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2 points by akkartik 11 days ago | link

I just made some tweaks to the Readme. What do you think?

https://github.com/akkartik/mu/commit/4650c8188f

https://github.com/akkartik/mu/blob/master/subx/Readme.md

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2 points by hjek 11 days ago | link

Yea, I think that's more inviting.

I got to try out the point of compiling and trying out your programs now. `ex8`, `ex9` and `ex10` all segfault here.

Some time ago I was at a wedding, and I was terribly bored, until I found out that the guy to my left was writing washing machine software in assembly. In a way it seems awfully primitive, e.g. your `ex11.subx` is 350 lines long and prints out `.......` but I guess in certain systems it's the only option, and what's underneath it all in any system.

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2 points by akkartik 11 days ago | link

Thanks for trying them out!

Those examples expect arguments at the commandline, and I chose not to perform error checking for an example :) The focus lay elsewhere for them. See the comment at the top for each.

ex11.subx is running a test for each of those dots :)

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3 points by hjek 12 days ago | link | parent | on: Show Arc: Debate (very alpha)

This is what's happening with my "I'm gonna rewrite News in Racket so I can get fast file uploads"-project. I settled on SQLite instead of Datalog, because SQLite is fast.

The score of an item is derived from the votes, not just a stored number. This should make `unvote` easy to implement.

Also, user text input is not forgotten, so there's no need for `unmarkdown`. (However I'm not claiming that my markdown implementation is appropriate)

Comment tree is displayed as list of lists, so folding should be easy to implement.

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3 points by hjek 17 days ago | link | parent | on: Ask: Collapsable Comments

I was looking at implementing that in Anarki a while ago thinking it would be simple.

But take a look at how it's implemented on HN. It's quite ... hacky, to say it nicely.

First, the way comments are represented in the HTML is as table rows stacked on top of each other, and indentation is done by stretching a transparent 1x1 gif. Assuming collapsible comments are to be implemented in JavaScript, you're in a bit of a pickle, because the comment tree has been flattened into a long list thereby making it difficult process in a sane way.

So how does HN do it? Well, have a look at the `ind` function in hn.js[0]:

    function ind (el) { return (byTag(el, 'img')[0] || {}).width }
Oh, yes, there is actually a function that returns the width of the invisible strecthed 1x1 gif used for indentation. And, `kidsOf` is implemented using `ind`, and so on.

Some time back, I changed Anarki to use fixed-width spaces for indentation in order to work on text-only browsers. I'm not sure that is any better, so if you want to take the same approach as HN, you'd have to revert Anarki back to invisible image indentation. And maybe you could just nab the collabsible comments code straight from hn.js?

I would personally consider it less hacky to represent the comment tree as a tree of nested list elements in the HTML in the first place. I just don't get this fear of `<li>`.

But whichever way you go about it, you should totally give it a shot!

But, well, even if you implement it in Anarki, it's not gonna go in this forum, I guess.

[0]: https://news.ycombinator.com/hn.js

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3 points by krapp 16 days ago | link

>I would personally consider it less hacky to represent the comment tree as a tree of nested list elements in the HTML in the first place. I just don't get this fear of `<li>`.

Apparently pg did it in part to be "unPC" in regards to HTML. (see the linked quote in the 'inline javascript' thread[0].) It is weird that, in the name of exploratory programming, he chose the most complicated and finicky layout imaginable just to stick it to the W3c and their rules, man.

Fortunately, I think Anarki is already moving in the right direction. Table layout should be almost entirely removed (I think polls still use it) and I've been adding css classes and IDs to make the HTML more amenable to scripting. Unfortunately, this means we can't really use anything from HN without rewriting it. There's still a bit more work to do in removing old html like fontcolor, etc.

But the interesting question would be where to store state? HN appears to have endpoints that handle it (?collapse=id) so I assume there is just a list of closed ids for each user somewhere on the server. It could probably also be done with local storage but that wouldn't persist across browsers.

[0]http://arclanguage.org/item?id=20788

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3 points by hjek 16 days ago | link

> But the interesting question would be where to store state? [...] It could probably also be done with local storage but that wouldn't persist across browsers.

Cool that you're working on this. Storing state on the server would also allow for it to work w/o JavaScript. (Yes, yes, I know, maybe everyone are not that much into progressive enhancement.)

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3 points by krapp 15 days ago | link

I'm working on improving the HTML, I don't know when if ever I'll get around to collapsible comments.

I was just pointing out that HN's own implementation is server-side, but doesn't have to be. As with voting, the js just makes changes to the DOM that shadow the actual work on the backend. I have no idea how to do it efficiently, though, since presumably each close/open operation would also mean an http request and possibly a file write.

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3 points by i4cu 15 days ago | link

> I have no idea how to do it efficiently, though, since presumably each close/open operation would also mean an http request and possibly a file write.

Which is the same for voting and page generation.

ie. Right now there's a big cost on the servers because all the work is done on the servers. If you start looking at it from the perspective of not adopting that cost then you might as well say the same for voting + all the html creation and just write the whole thing in js where you only fetch data.

This is the slippery slope that lead me to writing apps in clojurescript. For me, the workload may get increased, but much of the operational costs get distributed across the users and on their hardware.

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3 points by hjek 15 days ago | link

> Which is the same for voting and page generation. [...] Right now there's a big cost on the servers because all the work is done on the servers.

Yea, I don't think something like checking whether a comment is member of the list of hidden items by a user would really add workload of any significance.

> [...] you might as well say the same for voting + all the html creation and just write the whole thing in js where you only fetch data.

Does that not lead to an awful lot of traffic sometimes? (I'm imagining a version of News that would transmit all submitted content to let the client do the sorting and searching instead of doing it on the server.)

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3 points by i4cu 15 days ago | link

> I don't think something like checking whether a comment is member of the list of hidden items by a user would really add workload of any significance.

I don't think so either. My comment was that "all the work is done on the servers". For the whole app. That is looking at all of the cost in aggregate (every interaction requires a http request, and requires throttling, session handling, authentication, html page generation, and so on....).

> Does that not lead to an awful lot of traffic sometimes? (I'm imagining a version of News that would transmit all submitted content to let the client do the sorting and searching instead of doing it on the server.)

Sure if you fetch all data unsorted, but I wasn't suggesting (or at least thinking) anything like that. I was just suggesting the html creation and many interactions that currently represent at least half if not most of the workload the server operations are currently doing.

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3 points by i4cu 16 days ago | link

> Storing state on the server would also allow for it to work w/o JavaScript.

I agree for this case (surprise, surprise...). This app was/is designed to work without js (mostly). If there's much more of a departure from this design and any real dependancy on js begins, well really the whole app should get re-written.

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2 points by hjek 20 days ago | link | parent | on: Ask: Why is there no "save-list"?

Yep. Or change `save-table` to be an extension of `writefile` using `defextend`:

   (defextend writefile (val name) (is (type val) 'table)
     [the body of the save-table function here]

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2 points by rocketnia 20 days ago | link

Even if you merge `writefile` and `save-table` like this, but not `readfile1` and `read-table`, then people still need to know, at development time, what type of data is in the file in order to read it, so they might as well use a type-specific way to write it as well. Unfortunately, merging `readfile1` and `read-table` isn't really possible, since their serialized representations overlap; they can't reconstitute information that was never written to the file to begin with.

From a bigger-picture point of view, this seems like it would become a non-issue once Arc had its own reader. I assume the problem with reading tables using `read` is that Racket's reader constructs immutable hashes. An Arc-specific reader would naturally construct Arc's mutable tables instead.

Doesn't Racket's reader give us similar problems in that it reads immutable strings and cons cells, too? So these problems could all be approached as a single project.

In the short term, it's not a project that would need a whole new reader. It could just be an adaptation of Racket's existing reader... something like this:

  (define (correcting-arc-read in)
    (let loop ([result (read in)])
      (match result
        
        ; TODO: See if this should construct a Racket mutable cons cell
        ; instead (`mcons`). Right now this just creates an immutable
        ; one, which should be fine since Arc uses an unsafe technique
        ; to mutate those.
        [(cons a b) (cons (loop a) (loop b))]
        
        [ (? hash?)
          (make-hash
            (map
              (match-lambda [(cons k v) (cons (loop k) (loop v))])
              (hash->list result)))]
        [ (? string?)
          ; We construct a new mutable string with the same content as
          ; `result`.
          (substring result 0)]
        ; We handle tagged values, which are represented as mutable
        ; Racket vectors.
        [(? vector?) (list->vector (map loop (vector->list result)))]
        
        ; We handle various atomic values. (TODO: Add more of these
        ; cases until we've accounted for every writable type Arc
        ; supports. Alternatively, just make this a catch-all
        ; `[_ result]`.)
        [(? number?) result]
        [(? symbol?) result])))
Writing Arc's `queue` type might be tricky, since that representation relies on sharing. It's possible queues (and other tagged values in general) should have a customized read and write behavior.

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3 points by hjek 20 days ago | link

> I assume the problem with reading tables using `read` is that Racket's reader constructs immutable hashes.

Racket also has mutable hashes created using `make-hash`[0] rather than `hash`. It could just be that the tables are not serialised as something Racket reads as mutable hashes when deserialising it back again?

[0]: https://docs.racket-lang.org/reference/hashtables.html#%28de...

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3 points by rocketnia 20 days ago | link

"It could just be that the tables are not serialised as something Racket reads as mutable hashes when deserialising it back again?"

I'm pretty sure the Racket reader never reads a mutable hash, but that it's possible for a custom reader extension to do it.

Some of Racket's approach to module encapsulation depends on syntax objects being deeply immutable. In particular, a module can export a macro that expands to (set! my-private-module-binding 20) but which uses `syntax-protect` so that the client of that macro can't use the `my-private-module-binding` identifier for any other purpose. If the lists constituting a program's syntax were usually mutable, then it would be hard to stop the client from just mutating that expansion to make something like (list my-private-module-binding 20), giving it access to bindings that were meant to be private.

I think this is why Racket's `read-syntax` creates immutable data. As for why `read` does it too, I think it's just a case of `read` being a relatively unused feature in Racket. They don't have many use cases for `read` that they wouldn't rather use `read-syntax` for, so they don't usually have reasons for the behavior of `read` to diverge from the behavior of `read-syntax`.

All this being said, they could pretty easily add built-in syntaxes for mutable hashes, but I think it just hasn't come up. Who ever really wants to read a mutable value? In Racket, where immutable values are well-supported by the core libraries, you aren't gonna need it. In the rare case you want it, it's easy enough to do a deep traversal to build the mutable structure you're looking for (like my example `correcting-arc-read` does).

It only comes up as a particular problem in Arc. Arc's language design doesn't account for the existence of immutable values at all, so working around them when they appear can be a bit quirky.

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3 points by hjek 19 days ago | link

> I'm pretty sure the Racket reader never reads a mutable hash, but that it's possible for a custom reader extension to do it.

No..?

    > (require racket/serialize)
    > (define basket (make-hash))
    > (hash-set! basket 'fruit 'apple)
    > (write-to-file (serialize basket) "basket.txt")
    > (define bucket (deserialize (file->value "basket.txt")))
    > (hash-set! bucket 'fruit 'banana)
    > bucket
    '#hash((fruit . banana))

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4 points by rocketnia 19 days ago | link

The Racket reader reads a seven-element list there, not a mutable hash.

Looks like you're proposing to use a two-stage serialization format. One stage is `read` and `write`, and the other is `serialize` and `deserialize`. At the level of language design, what's the point of designing it this way? (Why does Racket design it this way, anyway?)

I can see not wanting to have cyclic syntax or syntax-with-sharing in the core language just because it's a pain in the neck to parse and another pain in the neck to interpret. Maybe that's reason enough to have a separate `racket/serialize` library.

But isn't the main issue here that Arc's `read` creates immutable tables when the rest of the language only deals with mutable ones? The mutable tables go through `write` just fine, but `read` doesn't read the same kind of value that was written out. If and when this situation is improved, I don't see where `racket/serialize` would come into play.

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2 points by hjek 18 days ago | link

> Looks like you're proposing to use a two-stage serialization format.

I wasn't really proposing anything, only pointing out that it's not the case that Racket never can read mutable hashes, and then illustrating that with a code example.

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3 points by rocketnia 18 days ago | link

Hmm, all right. I didn't want to believe that was the point you were trying to make. In that case, I think I must not have conveyed anything very clearly in the `correcting-arc-read` comment.

I've been trying to respond to this, which was your response to that one:

"Racket also has mutable hashes created using `make-hash` rather than `hash`. It could just be that the tables are not serialised as something Racket reads as mutable hashes when deserialising it back again?"

In the `correcting-arc-read` comment, I used `make-hash` in the implementation of `correcting-arc-read`, so I assumed your first sentence was for the edification of others. I found something to respond to in the second, which kinda pattern-matched to a question I had on my mind already ("Can't the Racket reader just construct a mutable table since what was written was a mutable table?").

As for my response to your "No..?"...

One of the purposes of `correcting-arc-read` is that (when it's used as a drop-in replacement for Arc's `read`) it makes `readfile1` return mutable tables. So if anyone had to be convinced that a reader that returned mutable hashes could be implemented at all in Racket, I thought I had shown that already. When it looked like you might be trying to convince me of something I had already shown, I dismissed that idea and thought you were instead trying to clarify what your proposed alternative to `correcting-arc-read` was.

Seems like I've been making bad assumptions and that as a result I've been mostly talking to myself. Sorry about that. :)

Maybe I oughta clarify some more of the content of that `correcting-arc-read` comment, but I'm not sure what parts. And do you figure there are any points you were making that I could still respond to? I'd better not try to assume what those are again. :-p

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3 points by kinnard 18 days ago | link

Sounds like I opened a can of . . . lists . . .

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3 points by akkartik 20 days ago | link

I have an old fork (https://github.com/akkartik/arc) that has an extensible generic pair of functions called serialize and unserialize which emit not just the value but also tagged with its type. read and write are built atop them.

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Just a guess: Maybe the Racket version shipped with Ubuntu Trusty Tahr is out of date? Perhap try adding the Racket PPA[0].

[0]: https://launchpad.net/~plt/+archive/ubuntu/racket

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2 points by hjek 27 days ago | link | parent | on: Knark - rewrite in plain Racket?

Have you done any web development in Clojure?

I like Clojure as a language, but I'm a bit overwhelmed with choice when it comes to web frameworks and the package managers you need to use those web frameworks (somewhat similar to Common Lisp), whereas with Racket and Arc there's just one place to start. Do you have any experience with Clojure web frameworks?

I'm always a bit scared of adding external dependencies to any project, but Rich Hickey has this great rant about semantic versioning where he argues that a new "major version" is essentially just a bad excuse for breaking existing stuff. I wonder if Clojure web libraries take those principles to heart or whether it's another left-pad incident waiting to happen?

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3 points by i4cu 27 days ago | link

This is a surprisingly difficult question to answer, but here I go...

FYI cljs = clojurescript.

When Clojure first came out there was a core set of libraries that everyone flocked to:

1. Compojure (a routing library)

  - similar to arc's defop
https://github.com/weavejester/compojure

example:

  (defroutes app
    (GET "/" [] "<h1>Hello World</h1>")
    (route/not-found "<h1>Page not found</h1>"))
1a. Ring (a middleware library)

  - parses the web request and converts it into a hash-map of meaningful values.
  - similar to srv.arc
https://github.com/ring-clojure/ring

2. Hiccup (HTML Soup)

  -  similar to hmtl.arc, but uses a data structure to provide flexibility.
https://github.com/weavejester/hiccup

example:

  [:head
    [:meta {:http-equiv "Content-type"
            :content "text/html; charset=utf-8"}]
    [:title "adder"]
    [:link {:href "/adder.css" :rel "stylesheet" :type "text/css"}]]
Much of this came about when people read example blogs like this:

https://mmcgrana.github.io/2010/07/develop-deploy-clojure-we...

note: it's a 2010 article so some of it's outdated, but the idea would be the same.

At that time everyone was racing to make more robust web frameworks. Many of them were from people doing the above stuff only adding features. However, shortly afterwards cljs was released and another slew of web frameworks came out as people embraced writing web apps client side. Then again, shortly afterwards, Facebooks React became the new thing and advanced the idea of further separating out the data content from the UI composing for rendering. At this point data models (i.e. big hash-maps) and syncing that data to the UI became the new norm. And even since then more advanced frameworks came out, such as Fulcro, that further extend the data modelling & syncing features (https://github.com/fulcrologic/fulcro).

Through out all this many web frameworks became abandon-ware and now it's really hard for a newbie to make sense of which one to use. In my opinion:

1. If you want to do what Arc does (server side page generation) then use Compojure + Hiccup.

2. If you want to write basic client side cljs code there are dom libraries like:

- Dommy https://github.com/plumatic/dommy

- Domina https://github.com/levand/domina

These are fairly simple to use.

2a. If you want to write client side cljs code that takes advantage of React then use Reagent. https://github.com/reagent-project/reagent (Much better more interesting that Domina/Dommy)

If you have a desire to enter the more advanced data-model-UI-syncing arena where I would probably use Fulcro (but haven't). Note that these advanced frameworks like Fulcro expect you to know much more about state management / data modelling and it could be a steep learning curve for some.

I've been developing cljs web apps for over 4 years. Over these years I've tried some of the frameworks, but I ended up writing my own as none of them could do what I needed.

Is that helpful?

All of that may seem like too much, but remember you really only need Compojure + Hiccup to be where Arc is at.

Edit: I just noted that you know Datalog, so I think Fulcro is a good fit for you (see http://book.fulcrologic.com/#GraphDB).

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2 points by hjek 27 days ago | link

> Is that helpful?

Yes! Thanks a lot for the write-up.

That Compojure example does look quite familiar and Arc-like, and looks like it can handle multipart post requests too[0].

I'd never heard of Fulcro before. Given what is often emphasised about Clojure, at first glance at the Fulcro docs I'm a bit surprised how often they mention state and mutations:

> The other very common case is this: You’ve loaded something from the server, and you’d like to use it as the basis for form fields. In this case the data is already normalized in your state database, and you’ll need to work on it via a mutation.[1]

Also, I'm too much into graceful degredation to ever go all out Cljs, unless it was for a phone app. But I find that it's often interesting to see how people do things in Clojure, even when not using that language, so I'll be giving those Fulcro videos a look.

[0]: https://github.com/whostolebenfrog/compojure-multipart

[1]: http://book.fulcrologic.com/#_initializing_in_a_mutation

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3 points by i4cu 27 days ago | link

> I'd never heard of Fulcro before. Given what is often emphasised about Clojure, at first glance at the Fulcro docs I'm a bit surprised how often they mention state and mutations:

Well things on the client side can be sometimes be mutable. No one gets around the fact the DOM is a mutable only object. But besides that, the Fulcro library has labelled one of their feature's a 'Mutation'. Which was probably a bad choice, but it has nothing to do with the immutability of the underlying cljs object that it uses for that "Mutation". You'll notice the example is using 'swap!'. That means it's modifying an atom; Where an atom is an interface to make changes to the immutable object it holds. So really 'swap!' takes the change request, constructs a new version the original thing held in the atom, with changes, then 'swap's it with the original item inside the atom. The original thing was never changed (no changes to existing slots in memory). Hence clojure's things are immutable, and they are in Fulcro too, accept when changing the DOM tree.

As for state that's mentioned all the time in Clojure :)

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2 points by akkartik 27 days ago | link

This is the Rich Hickey talk from 2016: https://www.youtube.com/watch?v=oyLBGkS5ICk. If you listen to it, it was made in an effort to adjust the community's trajectory. I too would like to hear if adjustments did happen.

Basically the way I interpreted it[1] is that "major version" is a meaningless concept. If you're making incompatible changes, rename the package. If that's a disincentive to making incompatible changes -- great!

[1] http://akkartik.name/post/versioning

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2 points by hjek 27 days ago | link

Nice blog post.

> Rich Hickey pointed out last year that the convention of bumping the major version of a library to indicate incompatibility conveys no more actionable information than just changing the name of the library.

Yes, I guess Hickey is applying this idea of immutability not only to data structures but also to APIs and even databases[0] with the proprietary database service Datomic. Interestingly Datomic uses Datalog as query language, so it's straight forward to apply at least some of those ideas with the Racket Datalog package[1].

As of now I have a basic web forum working with all data storage done in Datalog (except for file uploads!). I'll post some code once the design is a bit more settled. It's still in the breaking-things-all-the-time phase.

What I find a bit tricky about Datalog is that relations are stored together with other facts, which in my mind feels a bit like storing code in a database, but maybe I just haven't wrapped my head around it yet.

Does anyone here have favourite articles or talks about logic programming?

[0]: https://www.youtube.com/watch?v=EKdV1IgAaFc

[1]: https://docs.racket-lang.org/datalog/interop.html

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3 points by i4cu 27 days ago | link

> What I find a bit tricky about Datalog is that relations are stored together with other facts, which in my mind feels a bit like storing code in a database, but maybe I just haven't wrapped my head around it yet.

I can't speak for Datalog, but I've used Datomic.

If it's the same, then a 'fact' is comprised of an entity (the id), + an attribute, + a value.

The relationships are made by storing an entity id into the value slot of another fact. Thus the model is both flat (being a list of facts) and hierarchical (they can point to each other). It pretty much becomes a graph database. Is that what you mean?

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2 points by hjek 27 days ago | link

> I can't speak for Datalog, but I've used Datomic.

Cool!

> The relationships are made by storing an entity id into the value slot of another fact. Thus the model is both flat (being a list of facts) and hierarchical (they can point to each other). It pretty much becomes a graph database. Is that what you mean?

Yes, exactly! What I worry about (because I'm fairly new to logic programming) is whether it could potentially be difficult to update a program where storage of business logic and storage of data aren't separated?

If we assume we have a Hacker News web app where we have a fact: One day Alice submits a story with the title "How to peel onions"; and we are thinking "Why on earth did she post that here?!?" So we add this relation to our code: A story is `irrelevant` if it has the word "onion" in the title. Then, the next day we get another fact: Now Bob has submitted a story called "How onion routing works". This new story by Bob then makes us reconsider our definition of `irrelevant`.

In a typical imperative program we'd just edit the code and redefine the `irrelevant` predicate, and it would take effect next time we run the program (or instantly if we enter it at a repl). But here in our logic program we store this `irrelevant` relation in our graph database, so even though we have removed it from our code, it is still sitting there in the database along with all the facts, outside the reach and responsibility of git, or whichever VCS we're using.

Yes, so my question is: How do you practically deal with changes to business logic in logic programming where data storage and relation storage is one and the same? Perhaps Datomic just avoids this issue somehow? I may also be missing or misunderstanding something.

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3 points by i4cu 27 days ago | link

Can't say I know what the options are since I don't know Datalog or the DB you're using, but is this reasonable?:

  -----------------------------------------------------------
  Entity              | Attribute | Value
  -----------------------------------------------------------
  person-id-001       | name      | Alice
  person-id-001       | stories   | [story-id-001, story-id-002...]   

  story-id-001        | headline  | "How to peel onions"
  irrelevant-word-001 | stories   | [story-id-001, ...]
  irrelevant-word-001 | word      | onion
  -----------------------------------------------------------
So if you decide that onion is no longer irrelevant then delete the entity 'irrelevant-word-001'. Which seems, at least to me, better than making code pushes.

So all of this assumes a few things:

- Your DB supports a cardinality of 'many' items in the value slot.

- Your query language can perform joins.

Of course none of this helps when someone changes a headline, but only full-text search DB's will help you do that.

Edit: made edits.

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3 points by i4cu 27 days ago | link

To be complete (and somehow I edited this out):

  -----------------------------------------------------------
  Entity        | Attribute          | Value
  -----------------------------------------------------------
  globals       | irrelevant-words   | [irrelevant-word-001, ...]   
  -----------------------------------------------------------
So you would also need to remove the value 'irrelevant-word-001' from the above. At least this is how I would do it in Datomic anyway.

What's interesting (at least to me) is that Datomic has a function called 'retractEntity' [1] which auto-magically removes all references of an entity in any value slot when you retract the entity. Man I love Datomic :)

[1] https://docs.datomic.com/on-prem/transactions.html#dbfn-retr...

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2 points by hjek 27 days ago | link

> So if you decide that onion is no longer irrelevant then delete the entity 'irrelevant-word-001'. Which seems, at least to me, better than making code pushes.

I can make sense of that when there's just one instance of this app running. Yet imagine the scenario where the web app has been published, and suddenly other people are running this web app. If the business logic is then changed, somehow I'd have to tell those people: "Oh btw, when you're running `git pull` next time, then you just also gotta run this query to retract some of the old relations from the database."

Definitely not a problem for me yet, but I can just smell it coming. I could add those retractions to the code, but they would have to stay there indefinitely, because it's not possible to tell if those retractions have taken place on everyone's databases yet.

Maybe I'm over-thinking this.

> What's interesting (at least to me) is that Datomic has a function called 'retractEntity'

Looks like the one called `~` in Racket's Datalog[0].

[0]: https://docs.racket-lang.org/datalog/interop.html#%28form._%...

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2 points by i4cu 26 days ago | link

Quick questions before going further.

Is this irrelevant-word example a real feature you're building into the app or a contrived example to understand Racket DataLog DB use?

If it's a real feature, and I'm assuming it is. Then I'm also assuming that when a story is submitted you're parsing the title and adding the relationship to the current set of irrelevant-words that are stored.

So the question's are:

1. How are you going to remove the past relationships between stories and an irrelevant word that's getting removed? (looks like we've answered this).

2. How are you going to make sure past stories gain the relationship to newly added irrelevant words?

3. How are you going to handle title changes.

After you get handle on these then what you really need to do provide an interface, from within the apps admin tools, to trigger the noted functionality. This way the business logic is in the app and it's modifying the data.

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2 points by hjek 26 days ago | link

> Is this irrelevant-word example a real feature you're building into the app or a contrived example to understand Racket DataLog DB use?

It's a simplified and slightly contrived illustration of an issue in this pre-alpha code I haven't published yet, perhaps just because I haven't thought of a name for the project yet. But yes, let's assume it's a real feature for now.

> 3. How are you going to handle title changes.

I like Hickey's idea of accretion of data - with a timestamp! - and not forgetting previous facts. I think he's talking about it in The Database as a Value[0]. So, a story could have a few different titles in the database, and the newest one is the one you get to see.

The thing is, it's easy to add a timestamp to facts as a way of not considering old facts without forgetting them, but not to relations. For example in Racket Datalog[1]:

    (! (voted "i4cu" 'up 134))
can easily be get a timestamp:

    (! (voted "i4cu" 'up 134 1542151773))
but that would not really make sense in a relation like

    (! (root A B) (ancestor A B) (parent null A))
So, I don't feel there's a need for ever retracting facts, because timestamps solve that. (Even when deleting something, you could just add the fact that is has been deleted.) But with relations (a.k.a. business logic) I think I will need to retract things, which is tricky because this logic is not only present in the code but also in the database. This was the problem I was asking about.

> 2. How are you going to make sure past stories gain the relationship to newly added irrelevant words?

Datalog queries reflect the current set of facts and relations, so the possible irrelevance of a story would not be stored anywhere, so it wouldn't need to be updated.

> 1. How are you going to remove the past relationships between stories and an irrelevant word that's getting removed?

Some as above. For example, in a place oriented program a story object could have a boolean attribute `irrelevant?`, whereas I'm sending a query every time this value is needed, so no stale `irrelevance` attributes are stored anywhere.

> After you get handle on these then what you really need to do provide an interface, from within the apps admin tools, to trigger the noted functionality. This way the business logic is in the app and it's modifying the data.

Yes, that is kind of there already, as in having functionality for changing titles. The `irrelevant` functionality is not there now.

Ok, I think I just need to work on getting this code publishable, because it might be easier to discuss tangible examples.

[0]: https://www.infoq.com/presentations/Datomic-Database-Value

[1]: https://docs.racket-lang.org/datalog/interop.html

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2 points by i4cu 26 days ago | link

Yeah, Datomic doesn't expect the relationships to be stored in the DB. It stores a bunch of indexes for you and it has a great query language, but that's it.

So where will you're data be? In a local data structure? I read your racket Datalog link, but it doesn't show any details for the database side (i.e. durability etc.) even though it's labelled a database.

Also, I'm curious what made you choose a graph db. It seems like you're inheriting a lot of complexity and I'm wondering what the benefit is over a more traditional sql or nosql db.

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2 points by hjek 26 days ago | link

> So where will you're data be? In a local data structure?

Yes, I think. The database just stored in memory but it can be serialized and saved to the disk using `write-theory`[0] and loaded `read-theory`. That is what I'm doing for now, and it's a very naive and inefficient to do a full database dump rather than just appending new data, and I presume it's particularly in this area where Datomic is way more optimised and well thought out.

> Also, I'm curious what made you choose a graph db. It seems like you're inheriting a lot of complexity and I'm wondering what the benefit is over a more traditional sql or nosql db.

Well, I did the initial work on the web app: creating user accounts, adding posts and replies, and then I got to data storage. Initially I did a News-style flat-file database, just saving data as lists in files, that are then loaded into memory when the program starts. It mostly worked but also felt a bit complicated, and I thought that perhaps I should just use a proper database?

What I like about news.arc is that you can just launch it without any configuration, so MySQL and PostGreSQL were out of the question, and I started reading a bit about SQLite. But I've also had this fascination with logic programming, from what people are posting here[1][2], and from reading a bit of The Reasoned Schemer, and I watched some of those Rich Hickey talks again, where he talks about Datalog, which happens to be available for Racket.

There are just some things that are incredibly simple in declarative/logic programming. For example, if you have facts about stories being `parent` of their replies, then it's simple to just define the `ancestor` relation, and when you have the `ancestor` relation, you automagically get `descendants` without having to write any code, because it's just the inverse of `ancestor`:

    (! (:- (ancestor A B)
           (parent A B)))
    (! (:- (ancestor A B)
           (parent A C)
           (ancestor C B)))
But, I've also bumped into some questions - more practical than theorical - and that is why it's interested hearing about your experience with Datomic, and why I'm asking here.

So, SQLite is still on the table. I'm not too familiar with NoSQL, but my impression is that they are all about speed and scalability of data storage. I haven't used MongoDB but isn't it essentially just like storing JSON in a file, except faster? It would be interesting if any of those could be used in conjunction with Datalog though, if don't add too complexity for the sake of increased speed.

[0]: https://docs.racket-lang.org/datalog/interop.html#%28def._%2...

[1]: http://arclanguage.org/item?id=20650

[2]: http://arclanguage.org/item?id=20519

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2 points by i4cu 25 days ago | link

So a few things I wanted to point out:

Datomic vs. DataLog

Datomic uses DataLog as part of its query language, but that's pretty much where the comparison should end. Things like "treating the database as a value", and features such as data accretion that Rich talks about have nothing to do with DataLog. They're features of Datomic. So for example when you mention never retracting data, well your data size is going to continuously grow unless you write your own data management layer on top. Datomic, on the other hand, does this for you. When you want to query the database over time, then you're going to need to store time intervals for all of your data and incorporate that into each query. Where as in Datomic (which has a time log) you can pass in the DB itself as a value (with an associated time interval) and Datomic will make sure your queries are working against the dataset that accounts for the time interval.

I'm pointing this out because it seems to me that you're doing (or are going to be doing) a lot of work that may not be worth it for what you're trying to accomplish.

Nosql

> I'm not too familiar with NoSQL, but my impression is that they are all about speed and scalability of data storage.

Yes and No. Often speed can be a feature Nosql dbs advertise, but really, for me anyway, it's about flexibility and ease of use. Traditional RDBMS, for example, require creating schemas. Many Nosql databases don't require a schema at all which makes it easier to use and more flexible to change. Nosql's are often a key-value store so it can be really easy to take a hash-map or table of data from your code and just dump it into an nosql datastore and be able to query it.

My personal favourite is Redis and it might be worth considering for your app.

You can:

- store a value under a key [1]

- store table data [2]

- store values in a set [3] (which allows intersection/difference queries)

- store values in a sorted-set [4] (which allows you query by some numerical value like timestamp)

- use it to manage relationships [5]

The reasons I mention Redis is that the HN app is very well suited to it. HN only keeps 'x' amount of data in memory. And in Redis the data lives in memory. Also Redis allows you to set expiry times on data for auto eviction [6]. And Redis also supports ordered lists [7] which can make it useful for lisp based languages.

However it's not embedded. And if that's a requirement I'd almost suggest you move away from Racket and adopt a language that has more options for embeddable databases. I guess if you're willing to roll your own (and it looks like you may be) then that's awesome too.

But in case you decide otherwise... The library I use is Redis Carmine [8], but there are Racket clients [9].

1. https://redis.io/commands/set

2. https://redis.io/commands/mset

2a. https://redis.io/commands/mget

3. https://redis.io/commands/sadd

4. https://redis.io/commands/zadd

5. search: "Representing and querying graphs using an hexastore" https://redis.io/topics/indexes

6. https://redis.io/commands/expire

7. https://redis.io/commands/lset

8. https://github.com/ptaoussanis/carmine

9. https://redis.io/clients#racket

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2 points by hjek 25 days ago | link

> Datomic uses DataLog as part of its query language, but that's pretty much where the comparison should end. Things like "treating the database as a value", and features such as data accretion that Rich talks about have nothing to do with DataLog.

I'm not sure I totally agree with this. I think that apart from talking about the design of Datomic, he also has a more general point against what he calls PLOP (PLace Oriented Programming), which Datalog does address.

For example in plain Racket a value is lost if something else is put in its place:

    > (define foo 'bar)
    > (define foo 'baz)
    > foo
    'baz
In Datalog you just accrete facts:

    > (! (is foo bar))
    > (! (is foo baz))
    > (? (is foo X))
    is(foo, bar).
    is(foo, baz).
Hickey is also mentioning how git doesn't do PLOP in that it doesn't throw out your commit history (without you asking it to do so).

> The reasons I mention Redis is that the HN app is very well suited to it. HN only keeps 'x' amount of data in memory. And in Redis the data lives in memory. Also Redis allows you to set expiry times on data for auto eviction [6].

Interesting. Just checked news.arc, and yes `initload*` is set to 15000. Interesting idea from Redis with expiry times. I'll check it out. I hadn't considered the scenario of storing text enough to max out on memory, because it would probably be premature optimisation, but good to keep in mind. I'd like to give Redis/Rackdis a try; thanks for the suggestion. I've been hosting an Etherpad Lite instance, and Redis was painless to setup.

> I'm pointing this out because it seems to me that you're doing (or are going to be doing) a lot of work that may not be worth it for what you're trying to accomplish.

Yes, my priorities here are definitely to make the code as brief and simple as possible, and to not have to do to much work. With plain Datalog it's very little work to timestamp a fact, and it's also kind of necessary, e.g. to figure out which fact is most recent, when previous facts are not removed. I'm just trying to get the gist of Hickey's ideas here.

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2 points by i4cu 25 days ago | link

> PLOP (PLace Oriented Programming), which Datalog does address.

Yeah, I was thinking more along the lines that Datomic has built-in functionality to address the caching, cache eviction, and indexing that goes along with all that data accumulation. But you're correct, DataLog does accumulate facts.

> Interesting. Just checked news.arc, and yes `initload*` is set to 15000.

I did the same thing, about 6 or 7 years ago, that you're doing now. I ported HN to Clojure (which is actually how I learned Clojure). If memory serves me correctly when I was doing the work I realized I needed a real DB if I wanted to support load balancing. i.e. I needed to centralize the data for the authentication and fnid session info. I think Arc calls them fnids... You probably know better than I do now, but Arc has all this code to expire these session fnids and so, for me, Redis was just a good fit for that task.

Anyways, I'll be sure to take a look at the final result of your work.

Cheers.

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2 points by hjek 25 days ago | link

> I did the same thing, about 6 or 7 years ago, that you're doing now. I ported HN to Clojure (which is actually how I learned Clojure).

Cool!

> I needed to centralize the data for the authentication and fnid session info. I think Arc calls them fnids... You probably know better than I do now, but Arc has all this code to expire these session fnids and so, for me, Redis was just a good fit for that task.

The Racket web server is quite "batteries included" and comes with these different managers[0] for dealing with expiration of sessions/continuations, such as the LRU manager:

> The memory limit is set to `memory-threshold` bytes. Continuations start with 24 life points. Life points are deducted at the rate of one every 10 minutes, or one every 5 seconds when the memory limit is exceeded. Hence the maximum life time for a continuation is 4 hours, and the minimum is 2 minutes.

> If the load on the server spikes—as indicated by memory usage—the server will quickly expire continuations, until the memory is back under control. If the load stays low, it will still efficiently expire old continuations.

[0]: https://docs.racket-lang.org/web-server/servlet.html?q=respo...

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2 points by i4cu 24 days ago | link

> If the load on the server spikes...

When I was referring to load balancing and centralizing the data I was referring to many web servers sharing a centralized/external source for auth/session data.

I'm unfamiliar with racket's web server 'servlets'. The docs are little unclear (at least to me). Can these servlets live on a separate server so that the data can be shared between web servers? I'm guessing that was/is not a requirement for you, but I'm just interested in knowing if that's how it can work.

Uh oh, you're getting me interested in Racket now. I can't have that... I have too many projects :)

edit: I guess at the end of the day these servlets are web-servers right, so you can, even if you have to do it over http and build an api.

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2 points by hjek 24 days ago | link

> Can these servlets live on a separate server so that the data can be shared between web servers?

Probably. I assume that serializable continuations[0] from stateless servlets can just be stored wherever, like in Redis or something, instead of in the memory of one server.

> I ported HN to Clojure

If that is something you have published, it'd be fun to see, whether it's finished or not.

> Uh oh, you're getting me interested in Racket now.

My impression is that Clojure is faster, less verbose partly due to clever syntax and provides more immutable data structures than Racket. But when it comes to documentation and error messages, I find Racket more coherent and comprehensible.

Say, if I wanted to connect to a SQL databse, with Racket I'd use the DB module[1], end of discussion. But with Clojure there's Korma, ClojureQL, Persist, HoneySQL, Yesql, a JDBC wrapper from Clojure contrib, SQLingvo, oj, Suricatta, aggregate, Hyperion, HugSQL, and probably a few more[2][3]. That multitude of libraries with similar purpose may be useful in some cases, sure, but also potentially a bit overwhelming for beginners, so I guess that's why I found it easier to get started with Racket.

[0]: https://docs.racket-lang.org/web-server/stateless.html#%28pa...

[1]: https://docs.racket-lang.org/db/

[2]: https://stackoverflow.com/questions/294802/use-a-database-wi...

[3]: https://adambard.com/blog/clojure-sql-libs-compared/

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2 points by i4cu 23 days ago | link

> If that is something you have published, it'd be fun to see, whether it's finished or not.

I actually tried to look it out the other day during this conv, but it's buried somewhere unavailable right now. If I find/get to it I'll post.

> That multitude of libraries with similar purpose may be useful in some cases, sure, but also potentially a bit overwhelming for beginners, so I guess that's why I found it easier to get started with Racket.

Agreed. Navigating the volume libraries and the options available is a real pain in the beginning, but once you get past that, then it's not bad at all. At the same time, take a look at the quality of Clojure's Redis Carmine Library vs. Racket's Redis Libraries. Miles apart.

To each their own, right :)

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3 points by hjek 15 days ago | link

> take a look at the quality of Clojure's Redis Carmine Library vs. Racket's Redis Libraries.

Good point.

Anyways, I'm going with SQLite. It's really fast[0] and I just found out about recursive selects[1].

[0]: https://www.sqlite.org/fasterthanfs.html

[1]: https://sqlite.org/lang_with.html

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2 points by hjek 28 days ago | link | parent | on: Knark - rewrite in plain Racket?

Personally I think the way Arc deals with Racket interop is pretty solid (expect passing lists to Racket functions, as can be seen in app.arc). There's a lot to like about Arc: its terseness when compared to Racket and the anaphoric macros, but here's what pushed me to try out plain Racket:

- Arc is too slow to handle file uploads. Arc is not suitable for web apps that handle image and video upload.

- This is not a problem with Arc but with News: It relies a lot on state. I'm not a purist, but it is to an extend making it a bit difficult to hack on sometimes, e.g. the `unmarkdown` function because original input is "forgotten", and how the score of an item is just a numerical value rather than something that can be derived from voting data which makes `unvote` difficult to implement correctly.

- Racket has a nice way of just representing html as s-expressions, where with Arc it's functions and macros some of which return a value and some of which print to stdout. Also, a lot of the html in News is a bit hacky.

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3 points by hjek 41 days ago | link | parent | on: Tell Arc: Arc 3.2

Thanks for fixing the install instructions, too!

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