#18863: Subgroup doesn't work with number field unit group
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Reporter: katestange | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.8
Component: group theory | Resolution:
Keywords: unit group, number field, | Merged in:
subgroup | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: |
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Description changed by katestange:
Old description:
> I think we would like the following code to work:
>
> {{{
> N.<a> = NumberField(x^3+2)
> G = N.unit_group()
> g = G.random_element()
> G.subgroup([g])
> }}}
>
> But at the moment the last line produces a runtime error
> {{{
> RuntimeError: Gap produced error output
> Error, Variable: 'u1' must have a value
> }}}
>
> This is currently reproducible on the single cell sage server and sage
> cloud. It does not seem to depend on the number field in question.
>
> As far as I can tell, subgroup() is unable to recognise the input as
> elements of the group. I think the problem is that one cannot pass the
> argument 'names' when creating the unit group. For example, the
> following works:
>
> {{{
> H = AbelianGroup(1,[2],names=list("pqrst"))
> H.subgroup([H.random_element()])
> }}}
>
> but the following fails in exactly the same was as the unit group example
> {{{
> H = AbelianGroup(1,[2])
> H.subgroup([H.random_element()])
> }}}
New description:
I think we would like the following code to work:
{{{
N.<a> = NumberField(x^3+2)
G = N.unit_group()
g = G.random_element()
G.subgroup([g])
}}}
But at the moment the last line produces a runtime error
{{{
RuntimeError: Gap produced error output
Error, Variable: 'u1' must have a value
}}}
This is currently reproducible on the single cell sage server and sage
cloud. It does not seem to depend on the number field in question.
As far as I can tell, subgroup() is unable to recognise the input as
elements of the group. I think the problem is that one cannot pass the
argument 'names' when creating the unit group. For example, the following
works:
{{{
H = AbelianGroup(1,[2],names=list("pqrst"))
H.subgroup([H.random_element()])
}}}
but the following fails in exactly the same way as the unit group example
{{{
H = AbelianGroup(1,[2])
H.subgroup([H.random_element()])
}}}
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Ticket URL: <http://trac.sagemath.org/ticket/18863#comment:3>
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