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 a

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