penrose VS reactive-banana

There is a fork that compiles to js https://github.com/ghcjs/ghcjs compiler, and I believe the official glasgow compiler is working towards also supporting js/wasm (although I don't think they are supported as of yet).

I don't know anything about Haste, but you can get GHCJS 8.6 (or 8.10 with a bloated executable) via nix fairly easily or alternatively wait until the JS target recently merged into mainline ghc gets production ready: https://engineering.iog.io/2023-01-26-ghc-update.

Ah GHCJS does have this header: https://github.com/ghcjs/ghcjs/blob/ghc-8.10/lib/boot/data/include/stg/DLL.h

It seems like https://github.com/ghcjs/ghcjs/issues/821 is a rigid dealbreaker for any sizable project.

About the FFI: GHCJS extended the FFI to support inlined JS, named arguments, etc. See https://github.com/ghcjs/ghcjs/blob/master/doc/foreign-function-interface.md For now the JS backend only implements FFI calls similarly to native FFI. The rest will be open to discussion later (e.g. in a ghc-proposal) and should take into account the Wasm backend so that the same user code compiles with both backends as much as possible.

Other than that, I ran into a GHCJS and Miso bug, but they weren't too hard to solve.

There are a bunch of open branches. And yes, there is ghcjs support in haskell.nix, see this comment.

When I compile the ghc-8.8 branch locally, I get a number of test failures from the test suite. I'm not sure exactly how to fix them and they aren't currently my highest hobby priority.

As I grew up on a Macintosh, I was always interested in graphical user interfaces. In my free time, I'm currently working on refreshing my reactive-banana library so that it will hopefully work well with the upcoming JavaScript backend. (The library relies on a few non-trivial garbage collector features, which were not implemented in GHCJS a decade ago. Essentially, I ended up with a program that gave different results, depending on whether it was compiled with GHC native or with GHCJS. 😅)

Another FRP implementation that I think is quite simple is reactive-banana. Heinrich recently refactored the module hierarchy to stratify it based on low-level, mid-level and high-level abstractions: https://github.com/HeinrichApfelmus/reactive-banana/tree/master/reactive-banana/src/Reactive/Banana/Prim

I agree! Having foldMap be available in a monadic context is a big win - here's an example of me asking for it in reactive-banana, along with a motivating example - https://github.com/HeinrichApfelmus/reactive-banana/issues/222. Library authors, please consider adding these instances - your users will thank you!

There are some examples that also use event-switching, like https://github.com/HeinrichApfelmus/reactive-banana/blob/master/reactive-banana-wx/src/BarTab.hs , which also seems to use execute. They use <$ though instead of <$>: