Working on an implementation of free groups (ticket #12339), i have
found the following problem. I can loads-dumps free groups correctly,
but when i try to do the sme with free group elements, i get the
following error:
...
/home/mmarco/sage-5.0/local/lib/python2.7/site-packages/sage/
interfaces/expect.pyc in _check_valid(self)
1356 raise ValueError, "The %s session in which
this object was defined is no longer running."%P.name()
1357 except AttributeError:
-> 1358 raise ValueError, "The session in which this
object was defined is no longer running."
1359 return P
1360
My class has an attribute which is a gap object, and i guess that the
problem happens there. But the same is true for the free group class.
The init of FreeGroupElement is
def __init__(self,l=[],parent=None):
"""
TESTS:
::
sage: G=FreeGroup('a,b')
sage: x=G([1,2,-1,-1])
sage: x # indirect doctest
a*b*a^-2
sage: y=G([2,2,2,1,-2,-2,-1])
sage: y # indirect doctest
b^3*a*b^-2*a^-1
"""
if parent is None:
raise ValueError, "The parent must be provided"
if len(l)>0:
if (parent.rank()<max(l)) or (-parent.rank() > min(l)):
raise ValueError, "Generators not in the group"
self._gap_=gap(str(l)).AbstractWordTietzeWord(parent._gap_repr_.GeneratorsOfGroup())
self._TietzeList_=map(Integer,list(self._gap_.TietzeWordAbstractWord()))
Element.__init__(self,parent)
And the _init_ of FreeGroup is:
Element=FreeGroupElement
def __init__(self,arg1=None,arg2='x'):
"""
TESTS:
::
sage: G=FreeGroup('a,b') # indirect doctest
sage: G
Free Group on generators ('a', 'b')
"""
if isinstance(arg1,int) or arg1 in IntegerRing():
gens=normalize_names(arg1,arg2)
else:
gens=tuple(arg1.split(','))
self._gens_str_=tuple(gens)
if len(gens)==1:
strgen='("'+gens[0]+'")'
else:
strgen=str(self._gens_str_).replace("'",'"')
self._gap_repr_=gap('FreeGroup'+strgen)
self._gens_dict_=dict([(gens[i],self._gap_repr_.GeneratorsOfGroup()[i
+1]) for i in range(len(gens)-1)])
group.Group.__init__(self)
self._assign_names(gens)
Which would be the right way to implement this?
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