Hi:
Since there are some interesting error-correcting codes based on group
algebras over a finite field,
I'm making a stab at implementing group rings for permutation groups.
Dan Bump (offlist) suggested
looking at the CombinatorialAlgebra class in
sage.combinat.combinatorial_algebra.py. The docstring there
says, in part,
The CombinatorialAlgebra base class makes it easy to define and work
with new combinatorial algebras in Sage.
...
The important things to define are ._combinatorial_class which specifies
the combinatorial class that indexes the basis elements, ._one which
specifies the identity element in the algebra, ._name which specifies
the name of the algebra, ._prefix which is the string put in front of
each basis element, and finally a _multiply or _multiply basis method
that defines the multiplication in the algebra.
Baed on that, I'd like to input
class PermutationGroupRing(CombinatorialAlgebra):
def __init__(self, R, G):
self.group = G
self._combinatorial_class = PermutationGroupElement
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 have a command like
sage: PermutationGroupRing(ZZ,G)
return a group ring. Instead, I get the traceback error
{{{
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
/home/wdj/sagefiles/sage-3.0.3.rc0/<ipython console> in <module>()
/home/wdj/.sage/temp/hera/7513/_home_wdj_sagefiles_codes_group_rings_sage_6.py
in __init__(self, R, G)
27 self._name = 'Group ring of %s'%str(G)
28 self._prefix = ''
---> 29 CombinatorialAlgebra.__init__(self, R)
30 def _multiply_basis(self, a, b):
31 c = a*b
/home/wdj/sagefiles/sage-3.0.3.rc0/local/lib/python2.5/site-packages/sage/combinat/combinatorial_algebra.py
in __init__(self, R, element_class)
679 #Set the dimension
680 try:
--> 681 self._dim = self._combinatorial_class.count()
682 except (ValueError, NotImplementedError):
683 self._dim = None
AttributeError: type object
'sage.groups.perm_gps.permgroup_element.Permutation' has no attribute
'count'
}}}
which I can't decipher.
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:-)?
- David Joyner
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