It might not be necessary to (re)assign the global variable. Only if the user wants to do operations with the polynomial he wants an x to be that poly variable, and certainly not another x. So, the parser can do the part of figuring out what x is meant, maybe by checking all generator names. Example:
sage: ....charpoly() x + 1 sage: _ - x (parser sees underscore and operation, and an unassigned global, so it checks the object referred by the underscore for variable names) -- 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 sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
