Dear Chris, Many thanks for making the patch. From my side I revised once more clifford.cpp and change some varidx to idx. I also amend exam_clifford.cpp in away which checks metrics given by matrices both with idx and varidx. A strange thing occurred however. If I put both calls to macro CHECK6 one after another within clifford_check6 routine then compilation of exam_clifford.cpp on my computer never ends. Thus I separate them (rather ugly) to the second clone clifford_check6a. Best wishes, Vladimir -- Vladimir V. Kisil email: kisilv@maths.leeds.ac.uk -- www: http://maths.leeds.ac.uk/~kisilv/