#9457: power series equality fails when trailing coefficients are zero
-------------------------------------+-------------------------------------
Reporter: niles | Owner: malb
Type: defect | Status: needs_work
Priority: major | Milestone: sage-6.1
Component: commutative | Resolution:
algebra | Merged in:
Keywords: | Reviewers:
Authors: niles | Work issues: resolve problems with
Report Upstream: N/A | sha_tate.py
Branch: | Commit:
u/niles/ticket/9457 | e2219602a9d360f465ad79b098e4f923765ab791
Dependencies: | Stopgaps: #15748
-------------------------------------+-------------------------------------
Changes (by niles):
* stopgaps: => #15748
Old description:
> Comparison of power series uses `list` instead of `padded_list`. This
> drops trailing zeros, and means that power series equality is buggy:
>
> {{{
> sage: A.<t> = PowerSeriesRing(ZZ)
> sage: g = t + t^3 + t^5 + O(t^6); g
> t + t^3 + t^5 + O(t^6)
> sage: [g == g.add_bigoh(i) for i in range(7)] # these should all be
> True
> [True, False, True, False, True, False, True]
>
> sage: g.add_bigoh(3).list() # drops trailing zero
> [0, 1]
> sage: g.add_bigoh(3).padded_list()
> [0, 1, 0]
> }}}
>
> == Apply ==
>
> * [attachment:trac_9457_power_series_eq_rebase.patch]
New description:
Comparison of power series uses `list` instead of `padded_list`. This
drops trailing zeros, and means that power series equality is buggy:
{{{
sage: A.<t> = PowerSeriesRing(ZZ)
sage: g = t + t^3 + t^5 + O(t^6); g
t + t^3 + t^5 + O(t^6)
sage: g == t + O(t^3) # should be True
False
sage: [g == g.add_bigoh(i) for i in range(7)] # these should all be
True
[True, False, True, False, True, False, True]
sage: g.add_bigoh(3).list() # drops trailing zero
[0, 1]
sage: g.add_bigoh(3).padded_list()
[0, 1, 0]
}}}
--
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Ticket URL: <http://trac.sagemath.org/ticket/9457#comment:24>
Sage <http://www.sagemath.org>
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