On Sun, Jun 29, 2008 at 9:12 PM, William Stein <[EMAIL PROTECTED]> wrote:
>
> On Sat, Jun 28, 2008 at 11:47 AM, David Joyner <[EMAIL PROTECTED]> wrote:
>>
>> If you attach a file containing
>>
>> ##################################################################
>>
>> def PermutationGroupRing(R,G):
>> return PermutationGroupRing_generic(R,G)
>>
>> class PermutationGroupRing_generic(CombinatorialAlgebra):
>> def __init__(self, R, G):
>> self.group = G
>> self._combinatorial_class = G
>> self._one = G.identity()
>> self._name = 'Group ring of %s'%str(G)
>> self._prefix = ''
>> CombinatorialAlgebra.__init__(self, R)
>> def _multiply_basis(self, a, b):
>> c = a*b
>> return c
>> def group(self):
>> return self.group
>>
>>
>> ##################################################################
>>
>> then you get the following error:
>>
>> sage: F = GF(11)
>> sage: G = PermutationGroup([(1,2,3),(3,4,5)])
>> sage: attach "/home/wdj/sagefiles/codes/group_rings.sage"
>> sage: R = PermutationGroupRing(F,G)
>> sage: R.basis()
>> ---------------------------------------------------------------------------
>> TypeError Traceback (most recent call last)
>>
>> /home/wdj/sagefiles/sage-3.0.3.rc0/<ipython console> in <module>()
>>
>> /home/wdj/sagefiles/sage-3.0.3.rc0/local/lib/python2.5/site-packages/sage/combinat/combinatorial_algebra.py
>> in basis(self)
>> 701
>> 702 """
>> --> 703 return [self(x) for x in self._combinatorial_class]
>> 704
>> 705 def __call__(self, x):
>>
>> /home/wdj/sagefiles/sage-3.0.3.rc0/local/lib/python2.5/site-packages/sage/combinat/combinatorial_algebra.py
>> in __call__(self, x)
>> 738 return eclass(self, dict([ (e1,R(e2)) for
>> e1,e2 in x._monomial_coefficients.items()]))
>> 739 #x is an element of the basis combinatorial class
>> --> 740 elif isinstance(x, self._combinatorial_class.object_class):
>> 741 return eclass(self, {x:R(1)})
>> 742 elif x in self._combinatorial_class:
>>
>> TypeError: isinstance() arg 2 must be a class, type, or tuple of
>> classes and types
>> sage:
>>
>> I added the method
>>
>> def object_class(self):
>> return PermutationGroup_generic
>>
>> to PermutationGroup_generic so now,
>>
>> sage: R._combinatorial_class.object_class
>> <bound method PermutationGroup_generic.object_class of Permutation
>> Group with generators [(1,2,3), (3,4,5)]>
>> sage: R._combinatorial_class.object_class()
>> <class 'sage.groups.perm_gps.permgroup.PermutationGroup_generic'>
>> sage: isinstance(G,R._combinatorial_class.object_class())
>> True
>>
>> It seems to me the traceback error indicates I've defined object_class
>> incorrectly.
>> Does anyone have a hint as to the right way to go here?
>
> Maybe you should change
>
> elif isinstance(x, self._combinatorial_class.object_class):
>
> to
>
> elif isinstance(x, self._combinatorial_class.object_class()):
>
> William
Thanks but although that eliminated one traceback error, it created another.
Also, I'm worried that hacking Mike Hansen's combinatorial_algebra module
will create much more serious problems in other parts of SAGE.
I'm starting to think that either GroupRing should be written from scratch
(based closely on CombinatorialAlgebra) or else a GAP wrapper should be written.
I'm mostly interested in order to implement David Kohel's split group codes,
which generalize the duadic codes which have recently been implemented in
SAGE. Unfortunately, they rely heavily on abelian groups and their dual,
which is currently in a state of flux (I think David Roe is rewriting
it). So maybe
this should wait?
>
>>
>>
>>
>> On Sat, Jun 28, 2008 at 12:59 PM, David Joyner <[EMAIL PROTECTED]> wrote:
>>> On Sat, Jun 28, 2008 at 12:48 PM, Robert Bradshaw
>>> <[EMAIL PROTECTED]> wrote:
>>>>
>>>> On Jun 28, 2008, at 9:33 AM, David Joyner wrote:
>>>>
>>>>> On Sat, Jun 28, 2008 at 11:00 AM, John Cremona
>>>>> <[EMAIL PROTECTED]> wrote:
>>>>>>
>>>>>> It seems that what Dan Bump's instructions did not specify is what
>>>>>> properties the class assigned to ._combinatorial_class must have.
>>>>>> And it needs something which PermutationGroupElement does not have.
>>>>>>
>>>>>> Does that help?
>>>>>
>>>>> Okay. Maybe the best thing is to write a wrapper to GAP's GroupRing
>>>>> function.
>>>>
>>>> I disagree, using CombinatorialAlgebra will be a much better option.
>>>>
>>>>>>> Can anyone explain "AttributeError: type object
>>>>>>> 'sage.groups.perm_gps.permgroup_element.Permutation' has no
>>>>>>> attribute
>>>>>>> 'count'"
>>>>>>> (in words of two syllables or less, if possible:-)?
>>>>
>>>> Sure. It means that it's trying to use a method called "count" but
>>>> the class "Permutation" found in sage/groups/perm_gps/
>>>> permgroup_element doesn't define one. What you need to do is make a
>>>> method called count.
>>>>
>>>> Actually, looking at the code (and someone more familiar with sage-
>>>> combinat should correct me) it looks like _combinatorial_class should
>>>> be the Parent (i.e. the group) rather than the element. It would
>>>> probably make sense to do something like
>>>>
>>>>> class PermutationGroupRing(CombinatorialAlgebra):
>>>>> def __init__(self, R, G):
>>>>> self.group = G
>>>>> self._combinatorial_class = G # NOTE the change
>>>>> self._one = G.identity()
>>>>> self._name = 'Group ring of %s'%str(G)
>>>>> self._prefix = ''
>>>>> CombinatorialAlgebra.__init__(self, R)
>>>>> def _multiply_basis(self, a, b):
>>>>> c = a*b
>>>>> return c
>>>>
>>>> and add a count method to the group class.
>>>
>>> That worked! Thank you!
>>>
>>>>
>>>> - Robert
>>>>
>>>>
>>>> >>
>>>>
>>>
>>
>> >
>>
>
>
>
> --
> William Stein
> Associate Professor of Mathematics
> University of Washington
> http://wstein.org
>
> >
>
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