#5283: problem with posets: iterating the subposet construction
---------------------------+------------------------------------------------
Reporter: jhpalmieri | Owner: somebody
Type: defect | Status: new
Priority: major | Milestone: sage-combinat
Component: combinatorics | Keywords:
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If I try to create a subposet of a subposet of something, I have problems:
{{{
sage: P = BooleanLattice(2)
sage: above = P.principal_order_filter(0)
sage: Q = P.subposet(above)
sage: above_new = Q.principal_order_filter(Q.list()[0])
sage: Q.subposet(above_new)
---------------------------------------------------------------------------
AttributeError Traceback (most recent call
last)
/Users/palmieri/.sage/temp/Macintosh.local/16679/_Users_palmieri__sage_init_sage_0.py
in <module>()
/Applications/sage/local/lib/python2.5/site-
packages/sage/combinat/posets/posets.pyc in subposet(self, elements)
1036 raise ValueError, "not a list."
1037 for element in elements:
-> 1038 if element not in self:
1039 raise ValueError, "element not in self"
1040 relations = []
/Applications/sage/local/lib/python2.5/site-
packages/sage/combinat/posets/posets.pyc in __contains__(self, x)
272 else:
273 y = x
--> 274 return y in self._elements
275
276 def __call__(self,element):
/Applications/sage/local/lib/python2.5/site-
packages/sage/combinat/posets/elements.pyc in __eq__(self, other)
50 False
51 """
---> 52 return self.parent() == other.parent() \
53 and self.element == other.element \
54 and self.vertex == other.vertex
AttributeError: 'int' object has no attribute 'parent'
}}}
I think that the problem is in the {{{__contains__}}} method for posets,
where the argument x is converted to x.element, which might be an int.
I'm not sure why I have to iterate the subposet construction twice to get
this to happen...
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5283>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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