Reported to trac and fixed (I think).
http://sagetrac.org/sage_trac/ticket/1155
The link to the hg patch is in the ticket.
++++++++++++++++++++++++++++++
On 11/5/07, Carlo Hämäläinen <[EMAIL PROTECTED]> wrote:
>
> Hi,
>
> I'm doing some work with groups. Using gap.Image() I can get a
> permutation like this:
>
> sage: x
> (1,2)(3,7)(4,6)(5,8)
>
> But to make a permutation group out of this element I have to enclose
> the x in two sets of brackets:
>
> sage: PermutationGroup([[x]])
> Permutation Group with generators [(1,2)(3,7)(4,6)(5,8)]
>
> On the other hand, the following command fails (see below for code and
> output):
>
> sage: PermutationGroup([x])
>
> In my mind the second version is clearer - x is a permutation so [x]
> is a list of permutations and I should be able to use that to get a
> group.
>
> Should SAGE do a coercion here, or am I doing something in a strange way?
>
> Code and output:
>
> ----------------------------------------------------------------------
> | SAGE Version 2.8.11, Release Date: 2007-11-02 |
> | Type notebook() for the GUI, and license() for information. |
> ----------------------------------------------------------------------
>
> sage: p = 2
> sage: assert is_prime(p)
> sage:
> sage: F = gap.new("FreeGroup(3)")
> sage:
> sage: a = F.gen(1)
> sage: b = F.gen(2)
> sage: c = F.gen(3)
> sage:
> sage: rels = []
> sage: rels.append( a**Integer(p) )
> sage: rels.append( b**Integer(p) )
> sage: rels.append( c**Integer(p) )
> sage: rels.append( a*b*((b*a*c)**Integer(-1)) )
> sage: rels.append( c*a*((a*c)**Integer(-1)) )
> sage: rels.append( c*b*((b*c)**Integer(-1)) )
> sage:
> sage: N = gap.NormalClosure(F, gap.Subgroup(F, rels))
> sage: niso = gap.NaturalHomomorphismByNormalSubgroupNC(F, N)
> sage:
> sage: x = gap.Image(niso, a)
> sage: x
> (1,2)(3,7)(4,6)(5,8)
> sage: PermutationGroup([[x]])
> Permutation Group with generators [(1,2)(3,7)(4,6)(5,8)]
> sage:
> sage: PermutationGroup([x])
> ---------------------------------------------------------------------------
> <type 'exceptions.TypeError'> Traceback (most recent call last)
>
> /home/carlo/<ipython console> in <module>()
>
> /home/carlo/sage-source-current/local/lib/python2.5/site-packages/sage/groups/perm_gps/permgroup.py
> in PermutationGroup(x, from_group, check)
> 167 if not is_ExpectElement(x) and hasattr(x, '_permgroup_'):
> 168 return x._permgroup_()
> --> 169 return PermutationGroup_generic(x, from_group, check)
> 170
> 171
>
> /home/carlo/sage-source-current/local/lib/python2.5/site-packages/sage/groups/perm_gps/permgroup.py
> in __init__(self, gens, from_group, check)
> 212 elif not isinstance(gens, list):
> 213 raise TypeError, "gens must be a tuple or list"
> --> 214 gens = [gap_format(x) for x in gens]
> 215
> 216 cmd = 'Group(%s)'%gens
>
> >
>
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