On Wed, Dec 9, 2009 at 10:50 AM, Matt Bainbridge <bainbridge.m...@gmail.com> wrote: > Its easy enough to code this in sage. This seems to work over any > field:
Thanks. This is now http://trac.sagemath.org/sage_trac/ticket/7644 > > > def ps_inverse(f): > if f.prec() is infinity: > raise ValueError, "series must have finite precision for > reversion" > if f.valuation() != 1: > raise ValueError, "series must have valuation one for > reversion" > t = parent(f).gen() > a = 1/f.coefficients()[0] > g = a*t > for i in range(2, f.prec()): > g -= ps_coefficient((f + O(t^(i+1)))(g),i)*a*t^i > g += O(t^f.prec()) > return g > > def ps_coefficient(f,i): > if i >= f.prec(): > raise ValueError, "that coefficient is undefined" > else: > return f.padded_list(f.prec())[i] > > -- > To post to this group, send email to sage-support@googlegroups.com > To unsubscribe from this group, send email to > sage-support+unsubscr...@googlegroups.com > For more options, visit this group at > http://groups.google.com/group/sage-support > URL: http://www.sagemath.org > -- William Stein Associate Professor of Mathematics University of Washington http://wstein.org -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
