#14239: symbolic radical expression for algebraic number
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Reporter: gagern | Owner: davidloeffler
Type: enhancement | Status: needs_work
Priority: major | Milestone: sage-6.4
Component: number fields | Resolution:
Keywords: | Merged in:
Authors: Martin von Gagern | Reviewers: Marc Mezzarobba,
Report Upstream: N/A | Jeroen Demeyer
Branch: | Work issues:
u/gagern/ticket/14239 | Commit:
Dependencies: #17495, #16964 | 09683145989c437b59e02c02409d1dac05ac379d
| Stopgaps:
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Comment (by gagern):
Replying to [comment:86 jdemeyer]:
> OK, here is a compromise: remove the `via_nf` argument (just pretend
that it's always `True`), add fallback code only to `qqbar.py` (i.e. undo
df036339e25fcac24a3497b0cd74f4bf34d5816c) and clearly comment the fallback
code as being a fallback in case that Maxima's `solve` doesn't work.
I'm not convinced. The regression is for the case where Maxima could solve
the defining polynomial for the generator but not the minimal polynomial
for the element. While it might be hoped that applying pol_reduce to the
minimal polynomial of the element will lead to something Maxima can handle
again, I don't have any guarantees for this. And even if it works, it will
depend on the generator of some field used internally by qqbar, not the
declared generator of the number field where we started. I consider that
inferior. In addition to this, implementing `via_nf=True` without the
ability to pass `via_nf=False` in the recursive call would make that code
uglier as well.
So instead I'd drop the `via_nf` argument, expect it's always false and
only do the fallback to the generator for number field elements. Or in
other words, keep
[http://git.sagemath.org/sage.git/commit/?id=df036339e25fcac24a3497b0cd74f4bf34d5816c
df03633] but drop
[http://git.sagemath.org/sage.git/commit/?id=a4fa89444e8f8d8da082c4b91849cade8aca5f79
a4fa894]. Which is why I suggested in comment:80 to review stuff up to
[http://git.sagemath.org/sage.git/commit/?id=a5983f73b2acdbdd197f25d07c1fcf14bf1109e5
a5983f7].
--
Ticket URL: <http://trac.sagemath.org/ticket/14239#comment:87>
Sage <http://www.sagemath.org>
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