#13765: Cyclotomic embeddings should respect coercions.
-----------------------------------+----------------------------------------
Reporter: robertwb | Owner: davidloeffler
Type: defect | Status: needs_review
Priority: critical | Milestone: sage-5.7
Component: number fields | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Robert Bradshaw | Merged in:
Dependencies: | Stopgaps:
-----------------------------------+----------------------------------------
Old description:
> {{{
> sage: zC=(CC(-1)^(1/3))^2
> sage: Ka.<aa>=CyclotomicField(3,embedding=zC)
> sage: Kb.<bb>=CyclotomicField(3,embedding=zC^2)
> sage: Kc.<cc>=CyclotomicField(3,embedding=CC(17))
> sage: CC(aa)
> -0.500000000000000 + 0.866025403784439*I
> sage: CC(bb)
> -0.500000000000000 - 0.866025403784439*I
> sage: CC(Ka(bb))
> -0.500000000000000 + 0.866025403784439*I
> }}}
>
> It's better to disallow coercions between these then allow this nonsense
>
> {{{
> sage: CC(aa+bb)
> -1.00000000000000 + 1.73205080756888*I
>
> sage: CC(bb+aa)
> -1.00000000000000 - 1.73205080756888*I
> }}}
New description:
{{{
sage: zC=(CC(-1)^(1/3))^2
sage: Ka.<aa>=CyclotomicField(3,embedding=zC)
sage: Kb.<bb>=CyclotomicField(3,embedding=zC^2)
sage: Kc.<cc>=CyclotomicField(3,embedding=CC(17))
sage: CC(aa)
-0.500000000000000 + 0.866025403784439*I
sage: CC(bb)
-0.500000000000000 - 0.866025403784439*I
sage: CC(Ka(bb))
-0.500000000000000 + 0.866025403784439*I
}}}
It's better to disallow coercions between these then allow this nonsense
{{{
sage: CC(aa+bb)
-1.00000000000000 + 1.73205080756888*I
sage: CC(bb+aa)
-1.00000000000000 - 1.73205080756888*I
}}}
apply trac-13765-cyclo-embeddings.patch
--
Comment (by chapoton):
apply trac-13765-cyclo-embeddings.patch
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13765#comment:7>
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