Under the standard definitions, I believe this integral is divergent, so the
new answer is better than the old. In some cases, Maxima reports the
'principal value' of such integrals, with a warning message, which is
problematic because it's not clear how to communicate the warning
programmatically to systems like Sage.
-s
On Tue, Dec 22, 2009 at 10:26 AM, Karl-Dieter Crisman <kcrisman at gmail.com>wrote:
> We are hoping to upgrade the version of Maxima in Sage to 5.20, to
> take advantage of a number of recent improvements (particularly in
> solving). I am finding the following possible regression from 5.19.1
> to 5.20.0 (also in 5.20.1):
>
> 5.19.1
> (%i1) integrate(x*cos(-y*x),x,minf,inf);
> (%o1) 0
>
> 5.20.0
> (%i1) integrate(x*cos(-y*x),x,minf,inf);
> (%o1) <ascii art indicating the integral is returned as a nounform>
>
> This is with SBCL and ECL; I've logged it at
>
> http://sourceforge.net/tracker/?func=detail&aid=2919396&group_id=4933&atid=104933
>
> If there is an obvious easy patch for this, we can apply it ourselves
> for now and still put 5.20.1 in soon, which we would like to. Thanks
> for any assistance you can provide so close to the holidays!
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