On 02/15/2010 03:19 PM, Florent Hivert wrote:
Hi there,I have a slightly stupid question ! First of all consider the following behavior (sage 4.3.2): sage: A = MatrixSpace(ZZ, 3) sage: A.one() [1 0 0] [0 1 0] [0 0 1] sage: A.one()[1,2] = 1 sage: A.one() [1 0 0] [0 1 1] [0 0 1] This is definitely bad. It happens because one is generically computed by coercion from 1 and then cached without making it immutable. I see at least three solutions: 1. - Don't cache at all 2. - Return a cached immutable 3. - Return a mutable copy of a cached To have an idea of the usage I went trough the code: - MatrixSpace.identity_matrix implement 1. - MatrixSpace.zero_matrix implement 3. Of course, my opinion is to make those three methods implements 2. :-)
+1 for doing option (2). Jason -- 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
