On 4/15/07, Robert Miller <[EMAIL PROTECTED]> wrote: > There should be no difference between the matrices [[]] and [], > especially if they're printing as the same matrix. There is no > mathematical reason for having a matrix consisting of one row and zero > columns.
Yes there is. Most matrix algorithms have as corner cases either the number of rows or number of columns equal to 0. Two years ago John Cremona advocated strongly that I allow both cases, so SAGE would be much more pleasant to use than, say, LiDIA. I've done so, even though in many cases it was a surprising amount of extra work. For the record, MAGMA takes the same approach: sage: magma.RMatrixSpace(RationalField(),0,1) Full KMatrixSpace of 0 by 1 matrices over Rational Field > Even if there were, there doesn't seem to be a way to create > a matrix with zero rows and one column. Yes there is. sage: a = matrix(QQ,0,1,[]); sage: a.nrows(), a.ncols() (0, 1) > I'm of the opinion that [[]] > should be treated as having zero rows *and* zero columns. No. It has one row [], which has 0 columns. Printing doesn't determine objects in SAGE, so that a 0,1 and a 0,0 matrix print the same way isn't convincing. -- William > On Apr 13, 11:18 am, David Harvey <[EMAIL PROTECTED]> wrote: > > On Apr 13, 2007, at 2:08 PM, Robert Miller wrote: > > > > > sage: A = Matrix( GF(2), [[]] ) > > > sage: B = Matrix( GF(2), [[0]] ) > > > sage: A > > > [] > > > sage: B > > > [0] > > > sage: A.block_sum(B) > > > > > [0] > > > [0] > > > sage: A = Matrix( GF(2), [] ) > > > sage: A > > > [] > > > sage: A.block_sum(B) > > > [0] > > > > I don't understand the problem. In all cases, the number of rows of A > > plus the number of rows of B equals the number of rows of > > A.block_sum(B), and similarly for columns. What am I missing? > > > > david > > > > > -- William Stein Associate Professor of Mathematics University of Washington http://www.williamstein.org --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://sage.scipy.org/sage/ and http://modular.math.washington.edu/sage/ -~----------~----~----~----~------~----~------~--~---
