Dear Richard, It is nice to see that GiNaC received a serious revision. It also inspires some further contributions: I am attaching two small patches. All the best season wishes, Vladimir -- Vladimir V. Kisil http://www.maths.leeds.ac.uk/~kisilv/ Book: Geometry of Mobius Transformations http://goo.gl/EaG2Vu Software: Geometry of cycles http://moebinv.sourceforge.net/