Opened 12 years ago
Last modified 10 years ago
#10272 closed defect
laurent series truncate behaviour different from power series truncate — at Version 1
Reported by: | tkluck | Owned by: | malb |
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Priority: | minor | Milestone: | sage-5.1 |
Component: | commutative algebra | Keywords: | laurent series, truncate sd40.5 |
Cc: | Merged in: | ||
Authors: | Timo Kluck | Reviewers: | |
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description (last modified by )
There is the following difference in behaviour between truncate() for power series and laurent series:
sage: P.<p> = PowerSeriesRing(QQ) sage: L.<l> = LaurentSeriesRing(QQ) sage: f = p^2 + p^3 + p^5 +p^6 + O(p^7) sage: g = l^2 + l^3 + l^5 +l^6 + O(l^7) sage: f.truncate(6) p^5 + p^3 + p^2 sage: g.truncate(6) l^2 + l^3 + l^5 + O(l^6) sage: f.truncate_powerseries(6) p^2 + p^3 + p^5 + O(p^6)
The problem is simply that g.truncate() calls truncate_powerseries() on its underlying power series.
The attached patch changes LaurentSeries?.truncate() such that is calls truncate() on the underlying powerseries. For the current behaviour, it also adds a method truncate_laurentseries() which calls truncate_powerseries() on the underlying powerseries.
In my opinion, the methods truncate_powerseries and truncate_laurentseries are superfluous since they are equivalent to add_bigoh().