You can't run a lot of Crystal code in Ruby, either. They implement keyword arguments completely differently (Crystal does it more like Python, where all argume

You can't run a lot of Crystal code in Ruby, either. They implement keyword arguments completely differently (Crystal does it more like Python, where all arguments can be specified by name or position) and of course Ruby doesn't support Crystal syntax relating to types. Crystal also has a tuple type with a literal syntax ({1, 2, 3}) that isn't valid Ruby. But otherwise it's fairly close.