On Nov 16, 2007 2:07 AM, John Cremona <[EMAIL PROTECTED]> wrote: > Even before getting to Laurent series, multivariate power series are > harder to define than you might think, so I would avoid implementing > them at this point unless you have a specific need for them! You need > to be really careful since K[[x]][[y]], K[[y]][[x]] and K[[x,y]] are > not all the same.
I just want to counter with: Please *do* implement them! Numerous people involved with Sage have procrastinated implementing multivariate power series rings more times than I can count at this point. We need somebody unafraid to just do it. William > There are probably people on the list more knowledgeable than me about > this, but I thought it might be worth while posting a warning! > > John > > On 16/11/2007, David Roe <[EMAIL PROTECTED]> wrote: > > Hey all, > > At some point in the near future I may try to bring the implementation of > > power series rings more into line with the p-adics. The single variable > > case seems straightforward, but a something popped up for me when thinking > > about the multivariable case. > > > > What is the appropriate analogue of laurent series? Is the key point for > > laurent series that we allow bounded negative exponents? Or that it's a > > field? Because allowing bounded negative exponents is not enough to always > > have inverses: x + y has no inverse if we require the exponents of x and y > > to be bounded away from negative infinity. > > David > > > > > > > > > > -- > John Cremona > > > > > -- William Stein Associate Professor of Mathematics University of Washington http://wstein.org --~--~---------~--~----~------------~-------~--~----~ 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/ -~----------~----~----~----~------~----~------~--~---
