[mpweiher]

A couple of notes:

1. You seem to be confusing "dataflow constraints" with "dataflow". Though related, they are not the same.

2. Yes, the implementation of Rx-style "FRP" (should have used the scare quotes to indicate I am referring to the common usage, not actual FRP as defined by Conal Elliott) has deviated. And has deviated before. This also happened with Lucid.

3. However, the question is which of the two is the unnecessary bit. As far as I can tell, what people actually want from this is "it should work like a spreadsheet", so dataflow constraints (also known as spreadsheet constraints). This is also how people understand when used practically. And of course dataflow is also where all this Rx stuff came from (see Messerschmitt's synchronous dataflow)

4. Yes, the synchronous dataflow languages Lustre and Esterel apparently can be and routinely are compiled to state machines. In fact, if I understood the papers correctly the synchronous dataflow languages are seen as a convenient way to specify state machines.

5. It would probably help if you added some links to your papers.

[inglor]

Also, as someone who both works on open source reactive stuff (like MobX) and literally works on a spreadsheet app (Excel) I can say what we do is entirely different from what these systems do because of different constraints and both are reactive.

[aatd86]

I'm curious. How so?

[inglor]

In a gist: MobX just keeps the whole dependency graph of what data needs to update when what computed runs. Excel can't do that because it has to be able to work on large files with impartial data.

[aatd86]

Aren't excel formulas the expression of data dependency graphs?

In which case it is kept in the document?

[coldtea]

Isn't the Excel document still in memory?

[inglor]

Mathematically, RxJS and Vue/Solid Qwik like FRP are equivalent. There is interesting proof by Meijer (who invented Rx) in the famous "duality and the end of reactive". https://www.youtube.com/watch?v=SVYGmGYXLpY

[mpweiher]

> Mathematically, RxJS and Vue/Solid Qwik like FRP are equivalent.

Yes, these are basically the same thing. However, they have little to do with Conal Elliott's "FRP". Which itself is also badly named.

> Meijer (who invented Rx)

Well "invented". What's a bit surprising is that with both Rx and the Rx-style "FRP", there either is no public history of the ideas at all (Rx) or it is patently wrong (Rx-style "FRP"). Or a bit of both.

For example, the "Reactive" part of Rx-style FRP appears to come from the definition of system styles by Harel. Both the connection of synchronous dataflow with the term "Reactive" and with FP languages are made in the paper on Lustre, which is a language that integrates synchronous dataflow into an FP language. But there is nothing inherently FP-ish about synchronous dataflow, it was previously integrated into to the imperative language Esterel, and they also made a variant of C with synchronous dataflow.

Again, nobody mentions this, it is all presented as having been invented out of thin air and the principles of Functional Programming. (Or as having come from Conal Elliott's FRP, which is not true. Ask Conal Elliott).

Once I figured out the connections, I asked Erik Meijer, who has "I am the original inventor of Rx..." in his bio. He admitted that he was "inspired" by synchronous dataflow. And of course that is pretty much all it is. Except they dropped the requirement for it to be synchronous.

What do you get when you drop "synchronous" from "synchronous dataflow"? FRP, obviously ;-)

Just like Objective-C is Smalltalk + C, and Objective-C - C is ... Swift?

Controlling narratives is important.

[inglor]

All this is documented in Meijer's actual paper though? (Your mouse is a database) as well as his aformentioned talk (duality and the end of reactive).

He for sure invented observables (as we know it and as the mathematically dual of enumerables) - that doesn't mean it was the first ever reactive system or the concept of data being dependent of other data.

If I remember correctly he also explicitly talks abut Conal FRP and notations in https://www.youtube.com/watch?v=pOl4E8x3fmw if interested

[mpweiher]

I have seen plenty of Erik's talks and certainly read Your mouse is a database a bunch of times.

What is "documented" there is the alternate history of all this coming out of fundamental insights into FP and dualities and all that.

But that isn't the case, it just sounds a lot better than "I found a really complicated way to map dataflow onto FP concepts".

But we as an industry just love complicated.

[Paradigma11]

I think the important contribution of Meijer and RX is realizing the duality of IEnumerable and IObservable which enabled them to use the same programming constructs. The meat of RX is in all the combinators so you can express complex behaviours very succinctly.

[mpweiher]

Hmm...Smalltalk had the same iteration methods over streams and collections since at least Smalltalk-80, so not sure what the important contribution here is.

(Waiting for the LISPers to chime in...)

[inglor]

An observable is not the same as a Smalltalk stream, directionality wise. Smalltalk streams are like unix streams or a C stream.

[mpweiher]

Whether the flow is push or pull is a fairly irrelevant implementation detail for a dataflow system.

That doesn't mean it can't have big effects, but if you're relying on those, or they do become relevant, you should probably ask yourself whether your system is really dataflow.