#15303: Coercion discovery fails to be transitive
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Reporter: nbruin | Owner:
Type: defect | Status: needs_work
Priority: major | Milestone: sage-5.13
Component: coercion | Resolution:
Keywords: | Merged in:
Authors: Simon King | Reviewers:
Report Upstream: N/A | Work issues: Implement
Branch: | backtracking properly
u/SimonKing/ticket/15303 | Commit:
Dependencies: #14711 | 74821fe5409c3104b5d6eb7407a8287d54170df9
| Stopgaps:
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Comment (by SimonKing):
Oops, I spoke too soon. #12969 was in fact about backtracking for coerce
maps (not for actions), and forbidden paths are in fact declared
(`_register_pair(self, S,"coerce")`) if `discover_coerce_map_from()` is
called by `coerce_map_from()`.
That said, I wonder if the whole registration business couldn't be done
more efficiently. For example, the construction of coercions are
thoroughly based on the comparison of parents by identity (this even holds
for non-unique parents). Hence, `_register_pair` should be rewritten as
well, so that only identity and not equality counts. That's for a
different ticket.
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Ticket URL: <http://trac.sagemath.org/ticket/15303#comment:50>
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