MetaScala is an experimental metaprogramming library for Scala, including meta types for natural numbers, booleans, units, HList etc. The library is in pre-alpha stage, it's highly unstable and incompatible API changes can occur at any time. So use it only for experimentation at your own risk. :)
To compile the code you need a recent build of the Scala 2.8.0 compiler (the -Yrecursion compiler option no longer seems to be necessary). The code is released under the BSD license.