On Thu, Jun 24, 2010 at 7:28 PM, Robert Miller <r...@rlmiller.org> wrote:
> Today I helped Matt Greenberg solve (I think) a bug in modular symbols.
>
> His complaint was that the following does not work:
>
> sage: M = ModularSymbols(389,2,1,GF(7))
> sage: C = M.cuspidal_subspace()
> sage: N = C.new_subspace()
> sage: D = N.decomposition()
> sage: D[1].q_eigenform(10, 'a')
>
> After a while of poking around, the following patch made it work, but
> the change does not agree with the documentation of the function. I'd
> like advice on the proper way to fix this, and whether not this is
> correct:
I think this is a good idea. You can make the change below *and* also
change the docstring.
I wouldn't be surprised if this does perhaps break something somewhere
else, so be sure to test it well.
-- William
>
> diff -r 342fcdf4b4d3 sage/modular/modsym/heilbronn.pyx
> --- a/sage/modular/modsym/heilbronn.pyx Thu Jun 24 17:16:40 2010 -0700
> +++ b/sage/modular/modsym/heilbronn.pyx Thu Jun 24 19:27:36 2010 -0700
> @@ -534,6 +534,7 @@
> from sage.matrix.all import matrix
> from sage.rings.all import QQ
> T = matrix(QQ, len(indices), len(P1), sparse=False)
> + original_base_ring = R.base_ring()
> if R.base_ring() != QQ:
> R = R.change_ring(QQ)
>
> @@ -593,6 +594,8 @@
> sage.misc.misc.verbose("did reduction using dense multiplication",
> t, level=1,
> caller_name='hecke_images_gamma0_weight2')
>
> + if original_base_ring != QQ:
> + ans = ans.change_ring(original_base_ring)
> return ans
>
>
>
> --
> Robert L. Miller
> http://www.rlmiller.org/
>
> --
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--
William Stein
Professor of Mathematics
University of Washington
http://wstein.org
--
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