The Atlas project itself has some interesting stuff, including a custom programming language (http://www.liegroups.org/software/documentation/atlasofliegroups-d

The Atlas project itself has some interesting stuff, including a custom programming language (http://www.liegroups.org/software/documentation/atlasofliegroups-docs/library/axis.html http://www.liegroups.org/software/documentation/atlasofliegr...) with parts written in literate C++ (e.g. https://github.com/jeffreyadams/atlasofliegroups/blob/master/sources/interpreter/axis-types.w https://github.com/jeffreyadams/atlasofliegroups/blob/master...)!