Will you allow single-argument indexing as well? The Matlab convention is that indexing using a single argument indexes vec(A) instead of A. That's often useful, e.g., to update the diagonal of an nxn matrix, you could write A[::n+1] = 1.0.
More generally, it allows you to easily update a subset of the elements in A by writing A[I] = b where I is an index-set. Without single-argument indexing, you would need to write a loop for doing that. I think I raised the same question on the Scipy list long ago, and as I remember it the developers didn't like the idea. Personally, I like the convention, and it makes matrix computions more flexible than having to use a helper routine for things like that. Joachim On Mar 5, 4:21 pm, Dan Christensen <[EMAIL PROTECTED]> wrote: > "didier deshommes" <[EMAIL PROTECTED]> writes: > > SAGE now tries to support numpy (and matlab)-style indexing, by poking > > at its underlying __getitem__ and __getslice__ (thanks to a suggestion > > by William): > > Great! > > Another nice feature of numpy is *assigning* using numpy-style indexing. > For example, to add a multiple of column j to column i, you can do > > A[:,i] += m*A[:,j] > > And you can zero out a region with > > A[2:4, 3:8] = 0 (broadcasting used here) > > About the efficiency concern raised by William, does it work to first > assume the indices are not fancy, and if that fails, then catch an > exception and try to interpret them as numpy-style indices? > > Dan --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-support@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-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
