I’m not convinced it’s a question with an answer. To take Haskell for an example, there’s a GHC build on the depot. What does that mean?
Building Haskell on Haiku is a little challenging - I’ve done it and I wasn’t even trying to make a “port” out of it, so I know someone went to a lot of trouble to make that happen.
But it’s kind of an old port. People move on, and you can lose the committed maintainer just like that. GHC is a project where they’re always tinkering with the language, things have changed in the years since, and it may not be exactly ideal to live with that version indefinitely. Like to try upgrading? You can use that one to bootstrap, luckily because GHC depends on itself, and see how far you get.
I don’t think you’re going to get it working on 64 bits, though - I worked on that for a while, but there are problems with PIC code generation that no one else has because they don’t use ld -shared, and … I just came to the breakthrough realization that I was wasting my time with Haskell, seriously period.
That’s just my personal perspective, as someone who has spent a lot of time on it, and has an application of my own written in it, but am not the maintainer. Meanwhile – we’re in beta, which can affect how people think about committing to support a specific version, given that the platform underneath it hasn’t reached a final supported state (am I porting to the last beta release, or to a daily snapshot, …?)
And what’s more, since I’m already running on way too long here … the API is C++. I’m always fiddling around with this or that language binding, but don’t kid yourself, even if we can put up native BWindows and BListViews and so forth in that favorite language of ours, we’ll never quite have full access to the API. As it becomes more the Haiku API as opposed to Be API, that full access recedes even farther from reach. I haven’t tried binding the layout template stuff, but I’m not optimistic. What does “supported” really mean, then?