Which development language is used to create XSharp

The XSharp project will use two development languages to create its project:

1. The compiler itself is written in C#.
2. The macro compiler is also written in C#
3. The runtime system (such as the runtime functions and classes, RDDs etc) are written in X#
4. Many of the tools are written in X#

The source code of all of this is available on Github