#18940: Polynomials ignore the step argument in __getitem__
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Reporter: pbruin | Owner:
Type: defect | Status: needs_info
Priority: major | Milestone: sage-6.10
Component: algebra | Resolution:
Keywords: | Merged in:
Authors: Peter Bruin | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/pbruin/18940-getitem_step | 1c56779b3140d12fbe5d0973cdcad0ac9dbb8054
Dependencies: #19409 | Stopgaps:
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Comment (by jdemeyer):
One more thought. Let's call this '''degree-keeping slicing''':
{{{
sage: pol = PolynomialRing(QQ, 'x')(range(10))
sage: pol[3::2]
9*x^9 + 7*x^7 + 5*x^5 + 3*x^3
}}}
and let's call this '''degree-reducing slicing''':
{{{
sage: pol = PolynomialRing(QQ, 'x')(range(10))
sage: pol[3::2]
9*x^3 + 7*x^2 + 5*x + 3
}}}
The implementation of certain divide-and-conquer algorithms (e.g.
Karatsuba multiplication and FFT) can be expressed very easily using
degree-reducing slicing.
I'm not saying that this is a particularly strong argument for degree-
reducing slicing, since most likely you'd implement those algorithms using
lists instead of polynomials anyway.
--
Ticket URL: <http://trac.sagemath.org/ticket/18940#comment:39>
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