#12969: Coercion failures in symmetric functions
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Reporter: aschilling | Owner: sage-combinat
Type: defect | Status: new
Priority: major | Milestone: sage-5.3
Component: combinatorics | Resolution:
Keywords: symmetric functions, coercion | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by SimonKing):
In sage.structure.parent.Parent.coerce_map_from, I see the lines
{{{
#!python
mor = self.discover_coerce_map_from(S)
#if mor is not None:
# # Need to check that this morphism doesn't connect
previously unconnected parts of the coercion diagram
# if self._embedding is not None and not
self._embedding.codomain().has_coerce_map_from(S):
# # The following if statement may call this function
with self and S. If so, we want to return None,
# # so that it doesn't use this path for the existence
of a coercion path.
# # We disable this for now because it is too strict
# pass
# # print "embed problem: the following morphisms
connect unconnected portions of the coercion
graph\n%s\n%s"%(self._embedding, mor)
# # mor = None
if mor is not None:
# NOTE: this line is what makes the coercion detection
stateful
# self._coerce_from_list.append(mor)
pass
self._coerce_from_hash[S] = mor
}}}
Looks suspicious to me. A lost of commented-out code, and an empty special
case when the coercion is None.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12969#comment:5>
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