#20889: truncated power for polynomials
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Reporter: vdelecroix | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-7.3
Component: algebra | Resolution:
Keywords: | Merged in:
Authors: Vincent Delecroix | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/vdelecroix/20889 | d7d124e53af86ddf8b29f404f5b1b92ef42e7f61
Dependencies: | Stopgaps:
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Comment (by vdelecroix):
Replying to [comment:13 bruno]:
> I am sorry if I am becoming painful...
I wish I had every review like this one!
> * I would allow more general integers in `generic_power_trunc` to allow
computations as follows:
>
> {{{#!python
> sage: R.<x> = PolynomialRing(ZZ, sparse=True)
> sage: p = x^2^100 + 1
> sage: p.power_trunc(100, 2^100+1)
> 100*x^1267650600228229401496703205376 + 1
> }}}
I see. You mean for `prec`. As in your example, this would only be
interesting for sparse polynomials. Note that it will not work at all for
dense polynomials because `truncate` is defined as `cpdef Polynomial
truncate(self, long prec)`. I don't mind changing the generic method to
handle this case.
> * A curiosity question: Why did you write `generic_power_trunc` outside
from any class?
I did not have any other option. As you said we could have checked whether
the method `_power_trunc` is implemented in subclasses but this is not as
simple as it seems with `cpdef` methods.
--
Ticket URL: <https://trac.sagemath.org/ticket/20889#comment:14>
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