#14084: Wrong domain of the fraction field construction functor
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Reporter: SimonKing | Owner: nthiery
Type: defect | Status: new
Priority: major | Milestone: sage-5.7
Component: categories | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by nbruin):
... but
{{{
sage: k=Qp(7)
sage: k.category()
Category of commutative rings
sage: k in Fields()
True
sage: k.category()
Category of fields
}}}
which is a little uncomfortable in its own right. You'd think that a
category is part of the defining properties of the parent, so changing it
seems to fly into the face of immutability of parents.
If we have to keep it like this, we'd have to be very clear that one
should only test if a parent is IN a given category; never rely on the
category reported by "<parent>.category()". It certainly flies in the face
of what I thought sage did: I thought specifying a parent implied
specifying the category in which you want to consider it, and that if you
want to consider a number field as a `QQ`-vector space instead, one should
explicitly apply a functor and use a map (or perhaps conversion if you
want to be implicit about it) to go between the two.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14084#comment:3>
Sage <http://www.sagemath.org>
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