Dear All, I believe that |z|^2= z*conjugate(z) is valid for any z. Also, the automatic substitution abs(z)^(2n) -> z^n * conjugate(z)^n shall make an expression more rational and, thus, more accessible to GiNaC. Therefore, I propose the attached alteration of abs_power(). Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv@maths.leeds.ac.uk www: http://www.maths.leeds.ac.uk/~kisilv/ Book: Geometry of Mobius Transformations http://www.worldscientific.com/worldscibooks/10.1142/p835