#20400: Conversion NumberField -> QQbar should always work for rationals
-------------------------------------+------------------------
Reporter: vdelecroix | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.2
Component: number fields | Resolution:
Keywords: | Merged in:
Authors: Vincent Delecroix | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: #14485 | Stopgaps:
-------------------------------------+------------------------
Old description:
> After #14485 we have
> {{{
> sage: NF.<alpha> = NumberField(x^5 + 7*x + 3)
> sage: QQbar(alpha**5 + 7*alpha)
> Traceback (most recent call last):
> ...
> ValueError: need a real or complex embedding to convert number field
> element to algebraic number
> }}}
> but rationals are non ambiguous with respect to their embeddings.
New description:
After #14485 we have
{{{
sage: NF.<alpha> = NumberField(x^5 + 7*x + 3)
sage: QQbar(alpha**5 + 7*alpha)
Traceback (most recent call last):
...
ValueError: need a real or complex embedding to convert number field
element to algebraic number
}}}
but rationals are non ambiguous with respect to their embeddings.
See also the related #4621
--
Comment (by vdelecroix):
I propose
{{{
@@ -2373,8 +2374,7 @@ cdef class NumberFieldElement(FieldElement):
"""
emb = self._parent.coerce_embedding()
if emb is None:
- raise ValueError("need a real or complex embedding to convert
"
- "number field element to algebraic number")
+ return parent(self._rational_())
}}}
And also to wait for the next beta...
--
Ticket URL: <http://trac.sagemath.org/ticket/20400#comment:1>
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