#20889: truncated power for polynomials
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Reporter: vdelecroix | Owner:
Type: enhancement | Status: needs_work
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 | 7e24e7abb3c962d90f4c64ec14adae17fe3e1fd9
Dependencies: | Stopgaps:
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Comment (by vdelecroix):
Replying to [comment:5 bruno]:
> * How much does it gain to statically type the arguments of the method?
One drawback is that you cannot do the following (though the computation
would be fast):
>
> {{{#!python
> sage: p = 7
> sage: R.<x> = GF(p)[]
> sage: f = x^2 + x + 1
> sage: f.power_trunc(2^100, 1000)
> Traceback (most recent call last):
> ...
> OverflowError: long int too large to convert
> }}}
The reason is that I want to use library calls when available. Some of
them does not support arbitrary precision exponent. I used the type from
flint.
> * On a related note, do you think it may be useful to allow for a
negative power? The code could be as follows:
>
> {{{#!python
> if n < 0:
> return self.inverse_series_trunc(prec).power_trunc(-n, prec)
> }}}
I don't know. I do not think of `power_trunc` as a convenience function. I
want to use it in algorithms (like `nth_root`). We might propose
`_power_trunc_` (or `_power_trunc` or any other names) with restricted
types. And on the other hand `power_trunc` with arbitrary precision and
possibly negative input... Library calls would just override the
specialized function `_power_trunc_`. What do you think?
> * The first line of documentation is pretty terse...
I will change it.
--
Ticket URL: <https://trac.sagemath.org/ticket/20889#comment:6>
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