Thanks Vincent! What version of Sage are you using? With sage-9.8 I get:
---
from sympy import sympify
exp = sympify("CRootOf(x**5 + x + 1, 0)")
sage_poly = QQ['x'](list(map(QQ, reversed(exp.poly.rep.rep))))
sage_approx = RIF(exp.n()) + RIF(-1e-30, 1e-30)
QQbar.polynomial_root(sage_poly, sage_approx)
Outputs:
ValueError: Refining interval that does not bound unique root!
----
On Sat, Apr 1, 2023 at 12:02 PM vdelecroix <20100.delecr...@gmail.com> wrote:
>
> Dear Marcel,
>
> It is a pity that this does not work more directly. Here is a work around to
> achieve what you want to do
>
> sage: exp = sympify("CRootOf(x**5 + x + 1, 0)")
> sage: sage_poly = QQ['x'](list(map(QQ, reversed(exp.poly.rep.rep))))
> sage: sage_approx = RIF(exp.n()) + RIF(-1e-30, 1e-30)
> sage: QQbar.polynomial_root(sage_poly, sage_approx)
> -0.7548776662466928?
>
> This will be fixed in https://github.com/sagemath/sage/pull/35414 and
> hopefully included in the next sage version.
>
> Vincent
> Le vendredi 31 mars 2023 à 15:00:34 UTC+2, Marcel Moosbrugger a écrit :
>>
>> I am trying to convert "complex_root_of" expressions to algebraic numbers
>> (elements in the field QQbar). However, I get a "ValueError" with the
>> message "to many values to unpack".
>>
>> A minimal example would be:
>>
>> from sage.all import *
>> from sympy import sympify
>>
>> exp1 = sympify("CRootOf(x**2 + 1, 0)")._sage_()
>> exp2 = sympify("CRootOf(x**2 + 1, 1)")._sage_()
>> print(exp1)
>> print(exp2)
>> exp1 = QQbar(exp1)
>> exp2 = QQbar(exp2)
>> print(exp1)
>> print(exp2)
>>
>> The context I am working in is: I have a tool that is currently written in
>> python and sympy. I am trying to use the output of that tool to do some
>> further computation using sage, and the output of the first tool may contain
>> CRootOf expressions.
>>
>>
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