#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: analyse recursion
Branch: | error
u/SimonKing/ticket/15303 | Commit:
Dependencies: #14711 | f837cbee8f81c4946a92193c73e86449c53515d9
| Stopgaps:
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Comment (by SimonKing):
Replying to [comment:27 SimonKing]:
> 2. Let the user-provided morphism count for the number of morphisms
found in `.discover_coercion()`. Hence, if `num_paths=1` and the user
provides a morphism, then the maximal number of paths-to-be-considered is
attained and hence the user-provided morphism is returned without
backtracking.
>
> I think the second point is more important, and I will implement it now.
Note one remark in the code:
{{{
# If there is something better in the list, try to return
that instead
# This is so, for example, _coerce_map_from_ can return
True but still
# take advantage of the _populate_coercion_lists_ data.
}}}
The `_populate_coercion_lists_` data are also put into
`_coerce_from_cache`. Hence, these data will have priority over
`_coerce_map_from_` in `self.coerce_map_from(other)`. Therefore,
`self.discover_coerce_map_from(other)` will ''only'' be called if there
are no relevant `_populate_coercion_lists_` data.
Hence, I believe that the remark is not valid, and will remove it.
--
Ticket URL: <http://trac.sagemath.org/ticket/15303#comment:29>
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