#4276: [with patch, needs review] move number fields to new coercion, implement
embeddings
----------------------+-----------------------------------------------------
Reporter: robertwb | Owner: robertwb
Type: defect | Status: new
Priority: major | Milestone: sage-3.2.2
Component: coercion | Resolution:
Keywords: |
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Comment (by ncalexan):
I just discovered _populate_coercion_lists_(embedding=), and I am now a
lot happier. (Still not thrilled, because it caches aggressively and if
you do any arithmetic before changing the embedding it might not take.)
This is what I want to be able to do: (The composite fields call needs
new code of mine, to be posted shortly.)
{{{
sage: Q1 = NumberField(x^3 + 2, 'a')
sage: Q2 = NumberField(x^3 + 3, 'a')
sage: Q3 = Q1.composite_fields(Q2)[0]
sage: Q3, Q1_into_Q3, Q2_into_Q3, _ = Q1.composite_fields(Q2,
both_maps=True)[0]
sage: Q1._populate_coercion_lists_(embedding=Q1_into_Q3)
sage: Q2._populate_coercion_lists_(embedding=Q2_into_Q3)
sage: Q3(Q1.gen())
2/45*a0^7 + 7/45*a0^4 + 311/45*a0
sage: Q3(Q2.gen())
2/45*a0^7 + 7/45*a0^4 + 356/45*a0
sage: Q1.gen() + Q2.gen()
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
/Users/ncalexan/Documents/School/cmvar/cm_field.py in <module>()
----> 1
2
3
4
5
/Users/ncalexan/sage-3.2.1.alpha1/local/lib/python2.5/site-
packages/sage/structure/element.so in
sage.structure.element.ModuleElement.__add__
(sage/structure/element.c:5721)()
647
648
--> 649
650
651
/Users/ncalexan/sage-3.2.1.alpha1/local/lib/python2.5/site-
packages/sage/structure/coerce.so in
sage.structure.coerce.CoercionModel_cache_maps.bin_op
(sage/structure/coerce.c:5808)()
695
696
--> 697
698
699
TypeError: unsupported operand parent(s) for '+': 'Number Field in a with
defining polynomial x^3 + 2' and 'Number Field in a with defining
polynomial x^3 + 3'
}}}
I also want to assert an embedding of L into CLF and have the coercion
model discover that I can convert Q1 -> L -> CLF and Q2 -> L -> CLF. Then
we'll be getting somewhere.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/4276#comment:29>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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