#9621: Fix GAP interface problem in sylow_subgroup method
---------------------------------------------+------------------------------
Reporter: SimonKing | Owner: joyner
Type: defect | Status: closed
Priority: major | Milestone:
sage-duplicate/invalid/wontfix
Component: group theory | Resolution: duplicate
Keywords: GAP string representation | Work issues:
Report Upstream: N/A | Reviewers: Simon King,
Johan Sebastian Rosenkilde Nielsen, Mike Hansen
Authors: | Merged in:
Dependencies: | Stopgaps:
---------------------------------------------+------------------------------
Changes (by jdemeyer):
* status: positive_review => closed
* author: Simon King, Johan Sebastian Rosenkilde Nielsen =>
* reviewer: Mike Hansen => Simon King, Johan Sebastian Rosenkilde
Nielsen, Mike Hansen
* resolution: => duplicate
* work_issues: rebase =>
Old description:
> The following was reported by [http://groups.google.com/group/sage-
> support/browse_thread/thread/9fbca4e4dbadbe37 Kenny Brown]:
> {{{
> sage: n = 3^2 * 7^2
> sage: G = CyclicPermutationGroup(n)
> sage: G.sylow_subgroup(3)
> Traceback (most recent call last):
> ...
> }}}
>
> The problem is that in the sylow_subgroup method, it is attempted to get
> the string presentation of a permutation in GAP by calling gap.eval(...).
> However, GAP truncates the output. So, better use gap.eval('Print(...)')
> instead.
>
> Moreover, the method uses quite generic variable names in the GAP
> interface. This is dangerous, as the use of variable names that any
> average user might choose as well can have nasty side effects.
>
> The attached patch fixes both problems.
New description:
The following was reported by [http://groups.google.com/group/sage-
support/browse_thread/thread/9fbca4e4dbadbe37 Kenny Brown]:
{{{
sage: n = 3^2 * 7^2
sage: G = CyclicPermutationGroup(n)
sage: G.sylow_subgroup(3)
Traceback (most recent call last):
...
}}}
The problem is that in the sylow_subgroup method, it is attempted to get
the string presentation of a permutation in GAP by calling gap.eval(...).
However, GAP truncates the output. So, better use gap.eval('Print(...)')
instead.
Moreover, the method uses quite generic variable names in the GAP
interface. This is dangerous, as the use of variable names that any
average user might choose as well can have nasty side effects.
Fixed by #10334.
--
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9621#comment:9>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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