Look into F#.

It's open source. Works on Linux, Mac OS X, Android, iOS, Windows, etc. It has a good ecosystem and tooling built around it already but you can also tap into the C# ecosystem, if necessary.

It compares really well to Swift: http://www.slideshare.net/ScottWlaschin/swift-vslanguagex but even without that comparison, it's worth a look on its own.

I've looked into F# a few times. It's not ready on Mac. I wish people would quit suggesting until it's really baked.

Does it really work on iOS sans xamarian?

Have you looked into F#?

It's been open source for a while and there is a very good ecosystem that exists already for it. Plus the language itself is a pleasure to use.

No, I haven't looked into it much. I've been hesitant to commit too much to the CLR family, but maybe with MS's new stance on open source, I'll give it a second look. I'm also more interested now in languages that can deploy on mobile, so as alternatives to Julia, I'm actively looking into Swift, Go, or just plain C++. Xamarin is pretty compelling but I'm considering options before being locked into a fairly expensive vendor.

I would like to second the suggestion for F#. It has a nice balance in that it straddles the line between being an OSS ecosystem and an enterprise ecosystem with paid libraries. FsLab and Deedle got mentioned already but the F# website has a lot of great resources too: http://fsharp.org/guides/data-science/index.html

I found that Visual Studio Code is much faster than Atom, even though they are both built on Electron.