Dear All, I propose a tiny patch, which shall improve evaluation in GiNaC. abs() now can evaluate conjugates and step function. Power with real base and even-integer exponents reports that it is non-negative. Best wishes, -- 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