#20371: dispersion and dispersion sets of polynomials
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Reporter: mmezzarobba | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-7.2
Component: algebra | Resolution:
Keywords: | Merged in:
Authors: Marc Mezzarobba | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/mmezzarobba/20371-dispersion | 12dbbd7e433743d27324eb91bad13647abc5f255
Dependencies: | Stopgaps:
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Comment (by bruno):
A few remarks/questions:
* In the docstring of `dispersion_set` you have inconsistency between
`p,q` and `f,g`:
{{{
The dispersion set of `p` and `q` is the set of nonnegative integers
`n` such that `f(x + n)` and `g(x)` have a nonconstant common factor.
}}}
* It may be useful to mention that when the dispersion set is empty, the
dispersion you return is `-Infinity`. There is an example of the behavior,
but you may add it in the text.
* You use `assert` twice: Is there an example where the assertion does not
hold? If this is the case, it may be interesting to have a more meaningful
error message. If this is just to prevent an hypothetic future case where
some factorization algorithm does not respect this assertion, is it really
needed?
* In the first line of dispersion_set, you use a possibly useless
coercion. You may change this line to (I was not sure about the syntax but
it seems to work):
{{{#!python
other = self if other is None else other if other in self._parent else
self._parent.coerce(other)
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/20371#comment:2>
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