Travis, The zero module is not in the tensor category; its tensor product with anything else is 0. But it is the identity object for direct sums. I could see it being very helpful if, for example, one was implementing some formal Grothendieck group that didn't have a really convenient basis.
--Mark > Hey Nicolas and Mark, > Somewhat of a side remark: I think we should also have the 0 module > accessible as a special object in the category of modules (since it is the > terminal object and we might take tensor products). Actually, perhaps we > should have that object as a class which we can add in for isomorphic > objects (along with a method for constructing some instance of that class)? > For example, suppose I go > > sage: C = CombinatorialFreeModule(QQ, []) > > then C would inherit from a class, say TermialObject which has special > coercion properties and when tensored with another module M returns M back. > > Best, > Travis > > -- > You received this message because you are subscribed to the Google Groups > "sage-combinat-devel" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-combinat-devel+unsubscr...@googlegroups.com. > To post to this group, send email to sage-combinat-devel@googlegroups.com. > Visit this group at http://groups.google.com/group/sage-combinat-devel. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "sage-combinat-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-combinat-devel+unsubscr...@googlegroups.com. To post to this group, send email to sage-combinat-devel@googlegroups.com. Visit this group at http://groups.google.com/group/sage-combinat-devel. For more options, visit https://groups.google.com/d/optout.
