On Jul 30, 2007, at 12:26 PM, didier deshommes wrote:
> > 2007/7/30, Carl Witty <[EMAIL PROTECTED]>: >> It seems pretty strange to me, mostly because you lose too much >> information by eliding zeroes. As far as I can tell, given >> MPolynomialRing(QQ,2,order='lex'), all of the following polynomials: >> >> 3*x^2 + 1 >> 3*x^5 + x >> 3*y^7 + 1 >> 3*y + 1 >> >> would have a coefficients() list of [3, 1]. Is that true, and if so, >> is this really a useful function? > > For me it makes sense because I just need a method that iterates over > the coefficients of a polynomial. Having the ordering respected is a > little extra that I think helps the user. I could put the zeros in > there, but her are my own subjective reasons not to: > - I think of multivariate polynomials as sparse polynomials, so I > think coefficients() with the 0s omitted is OK. > - Maple does the same thing :) (I know, I know: not an argument...) > - Putting these zeros involves generating all the degree exponents, > which is slower. It can be done, but generating all the coefficients > this way for something like > f = x^6*y^12*z^2 > makes a big list made mostly of zeros. > > Here's a compromise: a paramater, (say all_coefficients) could be > specified to have an explicit list. Thoughts? Maybe it should be called coefficient_set to make it clear that the order does not preserve (much) information. --~--~---------~--~----~------------~-------~--~----~ 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/ -~----------~----~----~----~------~----~------~--~---
