I have explained it better in http://trac.sagemath.org/ticket/3354
but I'm still not sure if this is a bug, or the extend keyword behaves as expected, so please comment. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
