#10084: Lazy power series are created with incorrect order
-------------------------+--------------------------------------------------
Reporter: schilly | Owner: burcin
Type: defect | Status: new
Priority: major | Milestone: sage-4.6
Component: symbolics | Keywords:
Author: | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Reported by the "Report a Problem" Form:
When typing the following:
{{{
S = LazyPowerSeriesRing(ZZ)
one = S(0) + S(1)
one.order
}}}
I get a "Infinite series order" message. When asking for
{{{
one.coefficients(3)
}}}
I get "[0, 0, 0]".
Looking into the code sage/combinat/species/series.py, the _add_ method
calls the _new method to create the sum series. Trying:
{{{
zero = S(0)
test_series = zero._new(lambda ao: Stream(const=1), lambda: 0)
test_series.order
test_series.coefficients(3)
}}}
I again get "Infinite series order" and "[0, 0, 0]".
As I understand it, the _new() method calls the __init__() method of
!LazyPowerSeries in the line:
{{{
new_fps = self.__class__(parent, stream=None, order=unk,
aorder=self.aorder, aorder_changed=True, is_initialized=False)
}}}
If the value self.aorder is inf, this puts new_fps.aorder to inf, which
(in the __init__() code), also puts new_fps.order to inf, which makes Sage
think that the series has infinite order.
Changing the argument aorder=self.aorder to aorder=unk in the above line
solved the problem.
The sum of S(0) and S(1) should have order zero, and its first three
coefficients should be [1, 0, 0].
The series test_series should also have order zero, and its coefficients
should be [1, 1, 1].
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/10084>
Sage <http://www.sagemath.org>
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