Hi all, I just reviewed #8276 based on the discussion in http://groups.google.com/group/sage-devel/browse_frm/thread/1042edd11b3854b2 . For me a great problem arises with this change, though the majority voted for it. I think about it as follows.
The categories framework has introduced a function zero for every commutative monoid. Its standard definition is return self(0). MatrixSpace(...)(0) is mutable. Now, we overwrite this in matrix_space.py, which is an object of this category by zero = zero_matrix and zero_matrix returns an immutable matrix. Hence, zero returns a different value, than the framework implies and I am concerned about this. Still Sage lacks unification and for me the categories framework promised to change this by defining standard functions and their return values. I am not opposed to optimized implementation, but I am opposed to changing return values. Since, now, I will have to explain my students, that normally zero will return the same as self(0), but for MatrixSpaces the situation is slightly different. This is Pandora's box. I suggest to make zero as well as one just synonyms for self(0) and self(1), respectively, and leave zero_matrix and identity_matrix as they are. An alternative is to introduce a parameter for these last two functions immutable=True/False. What do you think about this? Martin -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
