A visual demo of Ruby's lazy enumerator
113 points by rossta 3 days ago | 23 comments
  • Lio 17 hours ago |
    That's lovely and makes it very obvious what's happening.
  • endorphine 17 hours ago |
    I was expecting a visual comparison towards the end of the article, where you would be able to click a button and both the eager and lazy versions would start executing simultaneously, one displayed next to the other, and you would clearly see that the lazy one completed earlier. This would make it even more obvious how the lazy one is faster.

    Nevertheless, this was great.

    • rossta 14 hours ago |
      Thanks for the feedback. I was thinking along those lines but settled on a version that let you toggle between the two. I’ll keep this in mind for next time though.

      There are probably a lot of fun variations to explore. Since this post seemed to resonate, I may be motivated to try some more experiments.

      • robocat 12 hours ago |
        I find horizontal/vertical is usually confusing (not to you obviously). Here is an example: https://www.investopedia.com/terms/h/horizontalanalysis.asp Maybe easier to stick with the lazy/eager wording?
        • rossta 11 hours ago |
          That’s fair. I acknowledge that terms like "horizontal" and "vertical" may be overloaded or even confusing, in this case, if it’s difficult to see the connection with the visuals. This is somewhat part of the risk in trying to explain a concept in a less-than precise way to introduce a new concept.
          • robocat 3 hours ago |
            I love the visuals - they are fantastic at showing the difference.

            If the visuals were vertical then the filtering might look more natural because time would be left-to-right and balls would have natural gravity and fall "down" through filters? Code runs top to bottom so I'm guessing it would still be clear.

            And putting a number in each of the balls might help clarity too :-)

            The only crazy thing is that Haskell lazy is pull (right) whereas Ruby lazy is still push - so the lazy keyword is somewhat confusing but that can't be fixed.

            I am not criticising and certainly don't want to make unnecessary work for you. Graphic design and animation are dark arts!

      • Exuma 8 hours ago |
        Your site is broken...
  • thih9 16 hours ago |
    Related discussion from yesterday:

    https://news.ycombinator.com/item?id=42652775 (different submitter; 29 points, 3 comments)

  • Syntaf 16 hours ago |
    Really cool visualization and neat to learn about lazy enumeration!

    Excuse me while I go back through my code and make sure I’m using lazy enumeration wherever I’m iterating over large collections….

    • dylan604 14 hours ago |
      This sounds like a similar response I had when learning about stream editors vs text editors. It was one of the killer apps that convinced to become a CLI warrior. Opening up a large text file in Notepad took for ever, but opening the same file in vim was a nothing burger. Then, the same person that showed me that showed me sed/awk/grep, and I was off to the races.
  • hakunin 15 hours ago |
    Lazy enumeration can also save memory, because you aren’t storing entire collections during intermediate steps, and it works with infinite/unknown size collections. Such as streaming data.

    Some examples:

    I wrote a utility gem a while ago that lets you lazily intersect, union, etc various potentially infinite streams of data. https://github.com/maxim/enum_utils/

    I also used lazy enumeration for traversing the wordmap in my no-RAM static storage gem. https://github.com/maxim/wordmap/

    • hansvm 13 hours ago |
      In the worst case, that must have intermediate space requirements equal to the entire collections, right?
      • hakunin 13 hours ago |
        I don’t think that can happen because all those functions assume the streams are consistently sorted.
        • hansvm 12 hours ago |
          Ohhhhh, nice. Yeah, sorted data is powerful. Thanks for pointing that out.
    • pyinstallwoes 12 hours ago |
      How is it different than a window, rolling window?
      • hakunin 12 hours ago |
        It's probably a version of that. But since data is assumed sorted, memory requirements almost never grow beyond one item per stream.
  • adsteel_ 14 hours ago |
    Hm, the CSS and JS don't appear to load for me. Not even a <body><html> set of tags in the HTML response.
    • fredrikholm 12 hours ago |
      Same here, both on computer and mobile. The rest of the website looks fine.
  • afraca 11 hours ago |
    When I learned Haskell in college I was blown away by how laziness enables cool things like dealing with infinite lists or more performance even though the UX is exactly the same. (Apparently with Ruby there is the slight hint of adding the lazy method in between)

    Later I found out laziness in the whole system by default leads to some difficult issues, which quite a few people seem to agree with. Simon Peyton Jones (Haskell co-creator) apparently has said "The next Haskell will be strict". (https://news.ycombinator.com/item?id=14011943)

    • drnewman 10 hours ago |
      Laziness is great for collections, and modeling the infinite but as a general model for programming it's a little loopy for my taste too ;-)
  • pansa2 2 hours ago |
    So in Ruby, `map` and `select` are eager-by-default, but you can just write `lazy.map().select()` to make the whole chain lazy? That's really nice - much better than Python 2, which was also eager-by-default and you had to change every function call to make it lazy (`map` => `imap`, `filter` => `ifilter`).

    Python 3 changed to being lazy-by-default. I assume that improves CPU/memory usage, but in some cases it does have less predictable behaviour. I can see why Ruby, with its goal of "developer happiness", would choose to retain the predictable behaviour of eager-by-default.

    • saagarjha an hour ago |
      Swift does this too, with almost the same syntax. IMO it's the right choice.
  • lukasb an hour ago |
    Apparently Typescript doesn’t have anything built-in like this?