The "2 * x" is rather - why would the reaction from a change in X display many gradual increments of 1 instead of showing the final value once? And then why does Z =Y+1 instead of +1 to Y repeats all the steps again from X? That's not how real signal frameworks work, and also not how you'd imagine they should work
Then the next cascading example: ok, if Signal is a button, not the underlying mechanism behind it, then "computed 1" is also a signal, why isn't it called that?
(though intuitively you'd think the moving dots are signals, not buttons)
I wrote a whole screed here about how glitches are evil and Rx is evil for teaching people they’re normal, but then I thought about it a bit more—
The system as described isn’t actually glitchy, is it? It doesn’t eagerly run any user computations, just dirtying, and that is idempotent so the order is irrelevant. It’s also a bit useless because it only allows you to pull out values of your own initiative, not subscribe to them, but that’s fixable by notifying all subscribers after the dirtying is done, which can’t cause glitches (unless the subscribers violate the rules of the game by triggering more signals).
So now I’m confused whether all the fiddly priority-queue needlepoint is actually needed for anything but the ability to avoid recomputation when an intermediate node decides it doesn’t want to change its output despite a change in one of its inputs. I remember the priority queue being one of the biggest performance killers in Sodium, so that can’t be it, right?..
I’m also confused about whether push-pull as TFA understands it has much to do with Conal Elliott’s definition. I don’t think it does? I feel like I need to reread the paper again.
Also also, some mention of weak references would probably be warranted.
I didn't know about Flapjax, thanks I'll check it out. Glitch-freedom is indeed a gap in this article. I focused on the signal algorithm exclusively without some implementation optimisation like batching updates; there is so much more to cover! Maybe in a next one, Thanks!
After wondering what the heck glitch-freedom is and learning about it, I agree with you. It seems like it deserves at least a brief explanation in an article about how signals work.
I've gone with the universal `alien-signals` package for my project (which doesn't use a frontend framework that includes signals). They show benchmarks of being by far the fastest and have strict limits on code complexity. Those limits are also supposed to avoid glitches by design, and now at least some of that is tested[1].
Beautiful presentation... @willybrauner, I would like to read your spin on a follow-up piece on `glitch-freedom`.
But in all honesty, this journal entry/post is a work of art; a testament to your journey as a technologist!.
Writing technical articles without adding a graphic and playful touch would indeed interest me less. I find that it's the intersection of these two worlds that makes reading enjoyable. Thanks for your kind words!
I do not want to distract from the content of the article, which is highly relevant for folks who built UIs with frameworks that are conceptually based on signals, but the way that the reading experience is designed really great, in particular the guided reading flow through the instructive code path is something that I rarely have seen done at all, and this even works pretty well on mobile. It's a delightful reminder on how a dynamic medium can be more than the simulation of print on screens.
I searched for the "right way" to explain this algorithm, and ultimately parsing the code was the clearest for me. This isn't always true; sometimes a graph or an interactive module has more impact; it really depends on the topic. Thanks for the feedback.
I create a new copy of the Set because the functions called during the loop might modify it by removing elements via cleanup functions. Without a copy, iterating directly on the Set could cause unpredictable behavior.
Thanks a lot! The left column containing the text is sticky, The right column is absolute and translate on Y and depend on an intersection observer triggered by each scroll section from the left.
I love this pattern, but I always felt like squeezing idiom B into idiom A when doing this in e.g. TS. I never tried effect-ts, so maybe I'm missing out. Anyone have experience in this?
The visual examples are rather misleading:
The "2 * x" is rather - why would the reaction from a change in X display many gradual increments of 1 instead of showing the final value once? And then why does Z =Y+1 instead of +1 to Y repeats all the steps again from X? That's not how real signal frameworks work, and also not how you'd imagine they should work
Then the next cascading example: ok, if Signal is a button, not the underlying mechanism behind it, then "computed 1" is also a signal, why isn't it called that? (though intuitively you'd think the moving dots are signals, not buttons)
Overall, very nice article. A few notes:
* I think the first implementation in JS land was Flapjax, which was around 2008: https://www.flapjax-lang.org/publications/
* The article didn't discuss glitch-freedom, which I think is fairly important.
I wrote a whole screed here about how glitches are evil and Rx is evil for teaching people they’re normal, but then I thought about it a bit more—
The system as described isn’t actually glitchy, is it? It doesn’t eagerly run any user computations, just dirtying, and that is idempotent so the order is irrelevant. It’s also a bit useless because it only allows you to pull out values of your own initiative, not subscribe to them, but that’s fixable by notifying all subscribers after the dirtying is done, which can’t cause glitches (unless the subscribers violate the rules of the game by triggering more signals).
So now I’m confused whether all the fiddly priority-queue needlepoint is actually needed for anything but the ability to avoid recomputation when an intermediate node decides it doesn’t want to change its output despite a change in one of its inputs. I remember the priority queue being one of the biggest performance killers in Sodium, so that can’t be it, right?..
I’m also confused about whether push-pull as TFA understands it has much to do with Conal Elliott’s definition. I don’t think it does? I feel like I need to reread the paper again.
Also also, some mention of weak references would probably be warranted.
I didn't know about Flapjax, thanks I'll check it out. Glitch-freedom is indeed a gap in this article. I focused on the signal algorithm exclusively without some implementation optimisation like batching updates; there is so much more to cover! Maybe in a next one, Thanks!
Batching isn't just an optimisation, not having transactional semantics can cause bugs.
And before there was "reactive", there were (oneway) dataflow constraints.
And a lot of literature on the algorithms.
I wrote a bit about the connection here:
https://blog.metaobject.com/2014/03/the-siren-call-of-kvo-an...
(It starts in a slightly different place, but gets there)
Also about constraints as an architectural connector.
https://dl.acm.org/doi/10.1145/2889443.2889456?cid=813164912...
After wondering what the heck glitch-freedom is and learning about it, I agree with you. It seems like it deserves at least a brief explanation in an article about how signals work.
I've gone with the universal `alien-signals` package for my project (which doesn't use a frontend framework that includes signals). They show benchmarks of being by far the fastest and have strict limits on code complexity. Those limits are also supposed to avoid glitches by design, and now at least some of that is tested[1].
[1]: https://github.com/stackblitz/alien-signals/pull/39
Beautiful presentation... @willybrauner, I would like to read your spin on a follow-up piece on `glitch-freedom`. But in all honesty, this journal entry/post is a work of art; a testament to your journey as a technologist!.
Cheers
Writing technical articles without adding a graphic and playful touch would indeed interest me less. I find that it's the intersection of these two worlds that makes reading enjoyable. Thanks for your kind words!
I do not want to distract from the content of the article, which is highly relevant for folks who built UIs with frameworks that are conceptually based on signals, but the way that the reading experience is designed really great, in particular the guided reading flow through the instructive code path is something that I rarely have seen done at all, and this even works pretty well on mobile. It's a delightful reminder on how a dynamic medium can be more than the simulation of print on screens.
I searched for the "right way" to explain this algorithm, and ultimately parsing the code was the clearest for me. This isn't always true; sometimes a graph or an interactive module has more impact; it really depends on the topic. Thanks for the feedback.
Why create an array each time it iterates a Set rather than just iterating the Set?
I create a new copy of the Set because the functions called during the loop might modify it by removing elements via cleanup functions. Without a copy, iterating directly on the Set could cause unpredictable behavior.
But as the article points out, this is a naive implementation. It could be discussed and greatly improved.
What an amazing article. I really like the presentation of text scrolling together with the code. Wonder how this is done under the hood.
Thanks a lot! The left column containing the text is sticky, The right column is absolute and translate on Y and depend on an intersection observer triggered by each scroll section from the left.
Nice presentation, looks like the same thing I implemented in Tcl here: https://wiki.tcl-lang.org/page/ReacTcl :-)
Sodium (and the book that goes with it) is a great resource too https://github.com/SodiumFRP/sodium
Now that Angular is adopting signals, building in it has become a much better experience.
Mind you, the framework still has a hostile learning curve, but for those who already made that investment, it's a boon.
How is error handling expected to happen here?
Result<T> should work
I love this pattern, but I always felt like squeezing idiom B into idiom A when doing this in e.g. TS. I never tried effect-ts, so maybe I'm missing out. Anyone have experience in this?
try-catch