#12322: invalid simplification of complex logarithm
-------------------------------------+-------------------------------------
Reporter: mjo | Owner: burcin
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.0
Component: symbolics | Resolution:
Keywords: | Merged in:
Authors: Michael Orlitzky | Reviewers:
Report Upstream: Reported | Work issues:
upstream. No feedback yet. | Commit:
Branch: | 36eff6f7a9a1f2da5dfafaa4a41ec4cc4ba068bf
u/mjo/ticket/12322 | Stopgaps:
Dependencies: #12737 |
-------------------------------------+-------------------------------------
Description changed by jdemeyer:
Old description:
> As pointed out by J.H. Davenport in this sage-support thread,
>
> http://groups.google.com/group/sage-
> support/browse_thread/thread/f9d2209041775c3e
>
> the following (invalid) log simplification is made:
>
> {{{
> sage: t = var('t')
> sage: assume(t, 'complex')
> sage: assumptions()
> [t is complex]
> sage: f = (1/2)*log(2*t) + (1/2)*log(1/t)
> sage: f.full_simplify()
> 1/2*log(2)
> }}}
>
> When, for example, t=-1,
>
> {{{
> sage: f(t = -1)
> I*pi + 1/2*log(2)
> }}}
>
> The assumption that `t` is complex is not necessary here, but simplify
> should ''definitely'' not ignore the imaginary part when dealing with
> complex functions.
>
> '''Apply''' [attachment:sage-trac_12322.patch]
New description:
As pointed out by J.H. Davenport in this sage-support thread,
http://groups.google.com/group/sage-
support/browse_thread/thread/f9d2209041775c3e
the following (invalid) log simplification is made:
{{{
sage: t = var('t')
sage: assume(t, 'complex')
sage: assumptions()
[t is complex]
sage: f = (1/2)*log(2*t) + (1/2)*log(1/t)
sage: f.full_simplify()
1/2*log(2)
}}}
When, for example, t=-1,
{{{
sage: f(t = -1)
I*pi + 1/2*log(2)
}}}
The assumption that `t` is complex is not necessary here, but simplify
should ''definitely'' not ignore the imaginary part when dealing with
complex functions.
--
--
Ticket URL: <http://trac.sagemath.org/ticket/12322#comment:18>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
--
You received this message because you are subscribed to the Google Groups
"sage-trac" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sage-trac.
For more options, visit https://groups.google.com/groups/opt_out.
