#7916: change conjugate(X) to try X.conjugate() [[this is easy!!]]
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Reporter: was | Owner: burcin
Type: defect | Status: new
Priority: minor | Milestone: sage-4.3.1
Component: calculus | Keywords:
Work_issues: | Author:
Upstream: N/A | Reviewer:
Merged: |
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{{{
On Tue, Jan 12, 2010 at 8:36 PM, jtyard <> wrote:
> Hi,
>
> I don't know if this counts as a bug, so sorry if I'm posting this to
> the wrong list. Say I define a cyclotomic field in Sage as follows:
>
> sage: Q3 = CyclotomicField(3)
> sage: z3 = Q3.0
>
> Then Sage can compute the complex conjugate independent of an
> embedding into the complexes:
>
> sage: z3.conjugate()
> -zeta3 - 1
>
> But I get a different answer by typing:
>
> sage: conjugate(z3)
> conjugate(e^(2/3*I*pi))
>
> Wouldn't it make sense for these to do the same thing? Another
> difference comes up as follows:
>
> sage: Q2.<s> = QuadraticField(-2)
> sage: s.conjugate()
> -s
> sage: conjugate(s)
> -I*sqrt(2)
>
> Yet, the problem doesn't exist with this slightly different
> definition:
>
> sage: QQ2.<ss> = QQ[sqrt(-2)]
> sage: ss.conjugate()
> -a
> sage: conjugate(ss)
> -a
Yes, I agree that this is a bug.
What is happening is that the *symbolic* conjugate function is coercing
its input X to the symbolic ring SR before applying itself. It would be
much better to test if X has a .conjugate method, and if so return that;
if not, then return SR(X).conjugate().
Here's the beginning of the course code for conjugate(X):
sage: conjugate.__call__??
# we want to convert the result to the original parent if the
input
# is not exact, so we store the parent here
org_parent = parent(args[0])
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/7916>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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