#13041: Conversion of number field elements to algebraic numbers
-------------------------------------+-------------------------------------
Reporter: rbeezer | Owner: AlexGhitza
Type: defect | Status: needs_work
Priority: minor | Milestone: sage-7.2
Component: algebra | Resolution:
Keywords: sd40.5 | Merged in:
Authors: Marc Mezzarobba | Reviewers: Vincent Delecroix
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/mmezzarobba/NFtoQQbar | 526e66c778c58e34086efd6ad5871ea84186520d
Dependencies: | Stopgaps:
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Comment (by mmezzarobba):
Replying to [comment:8 vdelecroix]:
> Why you can not go directly `NumberField -> IntervalField`? (i.e. the
FIXME in comment).
For example:
{{{
sage: C.<z> = CyclotomicField(7)
sage: a = 2*z^2 + 5*z^4
sage: CIF(a)
...
TypeError: unable to coerce to a ComplexIntervalFieldElement
sage: CIF(CLF(a))
-4.9498862074248? - 0.2195628712242?*I
}}}
> Is there a related ticket?
I don't know. I needed to convert number field elements to algebraic
numbers in experimental code of mine, so I wrote a small patch to make
that work in the cases I was interested in, but I didn't try to go to the
source of the problem...
> Indeed, the code will not work in some cases because of the following
> {{{
> sage: K = NumberField(x^3 - 2, 'cbrt2', embedding=RIF(1.25,1.26))
> sage: RLF(K.gen())
> Traceback (most recent call last):
> ...
> RuntimeError: maximum recursion depth exceeded while calling a Python
object
> }}}
Yes, the patch is far from perfect. Even so, I think it is an improvement
(and I don't have much time to work on a cleaner fix right now), but if
you disagree, I'll just keep my local patch for now!
--
Ticket URL: <http://trac.sagemath.org/ticket/13041#comment:9>
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