#13776: fix Element Constructor in CombinatorialFreeModule
------------------------------+---------------------------------------------
Reporter: chrisjamesberg | Owner: chrisjamesberg
Type: defect | Status: new
Priority: major | Milestone: sage-5.6
Component: combinatorics | Keywords: CombinatorialFreeModule
Work issues: | Report Upstream: N/A
Reviewers: | Authors: Chris Berg
Merged in: | Dependencies:
Stopgaps: |
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The method "_element_constructor_" within the class
"CombinatorialFreeModule" has a bug. The following code:
{{{
elif ((hasattr(self._basis_keys, 'element_class') and
isinstance(self._basis_keys.element_class, type) and isinstance(x,
self._basis_keys.element_class))
or (sage.structure.element.parent(x) == self._basis_keys)):
return self.monomial(x)
elif x in self._basis_keys:
return self.monomial(self._basis_keys(x))
}}}
will return a monomial indexed by that object before checking that x is an
element of the basis. For instance, in the current implementation of
kSchur functions, one can try:
{{{
sage: ks = SymmetricFunctions(QQ).kBoundedSubspace(3,1).kschur()
sage: ks(DyckWord([1,0,1,0]))
ks3()()
}}}
This should clearly be returning an error. For k-Schur functions, I have
fixed this in Track #13762, but was afraid to fix in general because I
didn't want to mess up functionality for others.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/13776>
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