On Thu, 30 Nov 2006 03:59:21 -0800, James Cranch <[EMAIL PROTECTED]> wrote:
> Dear William, > > I'd like an account for the SAGE bug tracker. What login name would you like? > I may as well write my bug report here. Whether you read it or not, > it'll be easy to copy and paste it over later. > > The routine "PowerSeriesRing_generic._is_valid_homomorphism_" in > power_series_ring.py seems to be coded incorrectly: there are often > valid ring homomorphisms out of R[[x]] sending x to 0 (say, from R[[x]] > to R itself), and these aren't recognised. You're right -- That's definitely a bug. And it's the same even in the latest pre-release alpha version of SAGE. > > A dialogue revealing the error follows below the email. > > I looked at the source code; the comments make me think this is a maths > error, not a coding error (insofar as the distinction matters). If you > agree that I'm not being stupid, I could patch it myself. > > By the way, how soon will bivariate or multivariate power series be > implemented? If not soon, I might have a go myself (but the result would > not be very efficient). There was a bunch of talk about this for SAGE at very points by Joe Wetherell and David Kohel, but they never implemented anything. And nobody else has brought it up since then. So it would probably be a long time until something is implemented if you don't do it. Thus I strongly encourage you to do it. > -------------------------------------------------------- > | SAGE Version 1.3.7.3.3, Build Date: 2006-09-21 | > | Distributed under the GNU General Public License V2. | > -------------------------------------------------------- > > sage: S = RationalField() sage: R.<t>=PowerSeriesRing(S) sage: R Power > Series Ring in t over Rational Field sage: H = Hom(R,S) sage: H([0]) > --------------------------------------------------------------------------- > exceptions.TypeError Traceback (most recent call last) > > /home/james/Documents/comp/sage/<ipython console> > > /home/james/installations/programming/sage/sage-1.3.7.3.3/local/lib/python2.4/site-packages/sage/rings/homset.py > > in __call__(self, im_gens, check) > > TypeError: images do not define a valid homomorphism sage: R.hom([0], S) > --------------------------------------------------------------------------- > exceptions.TypeError Traceback (most recent call last) > > /home/james/Documents/comp/sage/<ipython console> > > /home/james/Documents/comp/sage/gens.pyx in gens.Generators.hom() > > /home/james/installations/programming/sage/sage-1.3.7.3.3/local/lib/python2.4/site-packages/sage/rings/homset.py > > in __call__(self, im_gens, check) > > TypeError: images do not define a valid homomorphism > > > > --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] 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/ -~----------~----~----~----~------~----~------~--~---
