#14989: Conversion failure from `ZZ[i]` to `CC`
----------------------------------------------+----------------------------
Reporter: mmezzarobba | Owner:
Type: defect | Status:
Priority: major | needs_review
Component: misc | Milestone: sage-5.12
Keywords: | Resolution:
Authors: | Merged in:
Report Upstream: N/A | Reviewers:
Branch: u/mmezzarobba/ticket/14989 | Work issues:
Stopgaps: | Dependencies:
----------------------------------------------+----------------------------
Changes (by mmezzarobba):
* status: new => needs_review
* branch: => u/mmezzarobba/ticket/14989
Old description:
> `ComplexField_class._element_constructor_` calls
> `x.parent().polynomial()` when `isinstance(x,
> NumberFieldElement_quadratic)`, but not all objects of class
> `NumberFieldElement_quadratic` have a number field as a parent. As a
> consequence, the following conversion (that I guess really should work,
> since it is suggested by `pushout()`) fails.
>
> {{{
> sage: QQi.<i> = NumberField(x^2+1, embedding=1.*I)
> sage: O = QQi.order(i)
> sage: from sage.categories.pushout import pushout
> sage: pushout(O, CC)
> Complex Field with 53 bits of precision
> sage: CC(O.gen(1))
> ---------------------------------------------------------------------------
> AttributeError Traceback (most recent call
> last)
> <ipython-input-23-dbf70e6b573a> in <module>()
> ----> 1 CC(O.gen(Integer(1)))
>
> /home/marc/co/sage/local/lib/python2.7/site-
> packages/sage/rings/complex_field.pyc in __call__(self, x, im)
> 345 if im is not None:
> 346 x = x, im
> --> 347 return Parent.__call__(self, x)
> 348
> 349 def _element_constructor_(self, x):
>
> /home/marc/co/sage/local/lib/python2.7/site-
> packages/sage/structure/parent.so in
> sage.structure.parent.Parent.__call__ (sage/structure/parent.c:8134)()
>
> /home/marc/co/sage/local/lib/python2.7/site-
> packages/sage/structure/coerce_maps.so in
> sage.structure.coerce_maps.DefaultConvertMap_unique._call_
> (sage/structure/coerce_maps.c:3856)()
>
> /home/marc/co/sage/local/lib/python2.7/site-
> packages/sage/structure/coerce_maps.so in
> sage.structure.coerce_maps.DefaultConvertMap_unique._call_
> (sage/structure/coerce_maps.c:3757)()
>
> /home/marc/co/sage/local/lib/python2.7/site-
> packages/sage/rings/complex_field.pyc in _element_constructor_(self, x)
> 366
> 367 late_import()
> --> 368 if isinstance(x, NumberFieldElement_quadratic) and
> list(x.parent().polynomial()) == [1, 0, 1]:
> 369 (re, im) = list(x)
> 370 return complex_number.ComplexNumber(self, re, im)
>
> /home/marc/co/sage/local/lib/python2.7/site-
> packages/sage/structure/parent.so in
> sage.structure.parent.Parent.__getattr__ (sage/structure/parent.c:6662)()
>
> /home/marc/co/sage/local/lib/python2.7/site-
> packages/sage/structure/misc.so in
> sage.structure.misc.getattr_from_other_class
> (sage/structure/misc.c:1606)()
>
> AttributeError: 'AbsoluteOrder_with_category' object has no attribute
> 'polynomial'
> }}}
New description:
`ComplexField_class._element_constructor_` calls `x.parent().polynomial()`
when `isinstance(x, NumberFieldElement_quadratic)`, but not all objects of
class `NumberFieldElement_quadratic` have a number field as a parent. As a
consequence, the following conversion (that I guess really should work,
since it is suggested by `pushout()`) fails.
{{{
sage: QQi.<i> = NumberField(x^2+1, embedding=CC(0,1))
sage: O = QQi.order(i)
sage: from sage.categories.pushout import pushout
sage: pushout(O, CC)
Complex Field with 53 bits of precision
sage: CC(O.gen(1))
---------------------------------------------------------------------------
AttributeError Traceback (most recent call
last)
<ipython-input-10-dbf70e6b573a> in <module>()
----> 1 CC(O.gen(Integer(1)))
/home/marc/co/sage/local/lib/python2.7/site-
packages/sage/rings/complex_field.pyc in __call__(self, x, im)
345 if im is not None:
346 x = x, im
--> 347 return Parent.__call__(self, x)
348
349 def _element_constructor_(self, x):
/home/marc/co/sage/local/lib/python2.7/site-
packages/sage/structure/parent.so in sage.structure.parent.Parent.__call__
(sage/structure/parent.c:8134)()
/home/marc/co/sage/local/lib/python2.7/site-
packages/sage/structure/coerce_maps.so in
sage.structure.coerce_maps.DefaultConvertMap_unique._call_
(sage/structure/coerce_maps.c:3856)()
/home/marc/co/sage/local/lib/python2.7/site-
packages/sage/structure/coerce_maps.so in
sage.structure.coerce_maps.DefaultConvertMap_unique._call_
(sage/structure/coerce_maps.c:3757)()
/home/marc/co/sage/local/lib/python2.7/site-
packages/sage/rings/complex_field.pyc in _element_constructor_(self, x)
366
367 late_import()
--> 368 if isinstance(x, NumberFieldElement_quadratic) and
list(x.parent().polynomial()) == [1, 0, 1]:
369 (re, im) = list(x)
370 return complex_number.ComplexNumber(self, re, im)
/home/marc/co/sage/local/lib/python2.7/site-
packages/sage/structure/parent.so in
sage.structure.parent.Parent.__getattr__ (sage/structure/parent.c:6662)()
/home/marc/co/sage/local/lib/python2.7/site-
packages/sage/structure/misc.so in
sage.structure.misc.getattr_from_other_class
(sage/structure/misc.c:1606)()
AttributeError: 'AbsoluteOrder_with_category' object has no attribute
'polynomial'
}}}
--
Comment:
Hmm, the example I gave in the original ticket is not correct, since it
sets up an embedding into `SR`. But the same issue occurs with an
embedding into `CC`. I updated the description to reflect that.
I ''think'' the linked patches solve the problem, but I have no idea if
the "spirit" of the fix is right. So it would be great if someone who
understands the coercion system could have a look!
--
Ticket URL: <http://trac.sagemath.org/ticket/14989#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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