#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):
Good(?) news: I can track down the error to the following ''in vanilla
Sage''.
{{{
sage: L.<i> = NumberField(x^2 + 1)
sage: K = NumberField(L(i/2+3).minpoly(), names=('i0',),
embedding=L(i/2+3))
sage: from sage.rings.number_field import number_field_morphisms
sage: number_field_morphisms.EmbeddedNumberFieldMorphism(R, self)
Traceback (most recent call last):
...
RuntimeError: maximum recursion depth exceeded in __instancecheck__
}}}
The point is that the ''with my patch'', the above code is executed during
construction of K, in order to internally construct something. I'll ask on
sage-nt whether this code ''should'' give a map. I guess it should not,
but perhaps the number theorists disagree. And if it should not give a
map, then the should be a `TypeError` raised, without infinite recursion.
--
Ticket URL: <http://trac.sagemath.org/ticket/15303#comment:55>
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