On Sat, Nov 29, 2008 at 2:36 PM, Dieter Kaiser <drdieterkaiser at web.de>wrote:
> ...When we look at the expression we get a wrong result too:
>
> (%i54) (-1)^(1/3);
> (%o54) -1
>
> We also get the wrong result with a rectform:
>
> (%i59) rectform((-1)^(1/3));
> (%o59) -1
> ...
> Maxima does the wrong simplification for all rational exponents which have
> an
> odd integer in the denominator e.g 1/5, 2/5, 3/5, ... 1/7, 2/7, 3/7, ...
> For an
> even integer in the denominator an unsimplified result is returned.
>
> I think this is a serious error and I am wondering if we have further bugs
> related to this wrong simplification.
>
This is not a bug or a "serious error". It is a design decision to give the
real root in these cases when domain = real (the default). Mirabile dictu,
this is even documented pretty clearly -- see domain and m1pbranch in
http://maxima.sourceforge.net/docs/manual/en/maxima_35.html.
You may disagree with this design decision, but that doesn't make it a
"bug".
-s