#17428: wrong limit in derivative
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Reporter: wonder | Owner:
Type: PLEASE CHANGE | Status: new
Priority: major | Milestone: sage-6.5
Component: PLEASE CHANGE | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by wonder:
Old description:
> I'm seeing this behavior in sage 6.4, just built from git:
>
> {{{
> $ ./sage
> ┌────────────────────────────────────────────────────────────────────┐
> │ Sage Version 6.4, Release Date: 2014-11-14 │
> │ Type "notebook()" for the browser-based notebook interface. │
> │ Type "help()" for help. │
> └────────────────────────────────────────────────────────────────────┘
> sage: e = SR('a*f(x)+g(x)')
> sage: e
> a*f(x) + g(x)
> sage: e.limit(x=0)
> limit(a*f(x) + g(x), x, 0)
> sage: e.limit(x=0).limit(a=0)
> limit(g(x), x, 0)
> sage: de = diff(e,SR('x'))
> sage: de
> a*D[0](f)(x) + D[0](g)(x)
> sage: de.limit(x=0)
> limit(a*D[0](f)(x) + D[0](g)(x), x, 0)
> sage: de.limit(x=0).limit(a=0)
> D[0](g)(x)
> }}}
> The last result should be `limit(D[0](g)(x), x, 0)`.
>
> For reference, this report was also
> [https://groups.google.com/forum/#!topic/sage-devel/9NcuLzIUNXY posted to
> sage-devel].
New description:
I'm seeing this behavior in sage 6.4, just built from git:
{{{
$ ./sage
┌────────────────────────────────────────────────────────────────────┐
│ Sage Version 6.4, Release Date: 2014-11-14 │
│ Type "notebook()" for the browser-based notebook interface. │
│ Type "help()" for help. │
└────────────────────────────────────────────────────────────────────┘
sage: e = SR('a*f(x)+g(x)')
sage: e
a*f(x) + g(x)
sage: e.limit(x=0)
limit(a*f(x) + g(x), x, 0)
sage: e.limit(x=0).limit(a=0)
limit(g(x), x, 0)
sage: de = diff(e,SR('x'))
sage: de
a*D[0](f)(x) + D[0](g)(x)
sage: de.limit(x=0)
limit(a*D[0](f)(x) + D[0](g)(x), x, 0)
sage: de.limit(x=0).limit(a=0)
D[0](g)(x)
}}}
The last result should be `limit(D[0](g)(x), x, 0)`.
For reference, this report was also
[https://groups.google.com/forum/#!topic/sage-devel/9NcuLzIUNXY posted to
sage-devel].
--
--
Ticket URL: <http://trac.sagemath.org/ticket/17428#comment:1>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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