The change occured somewhere in between 5.9.3 and 5.10.0
Maxima 5.9.3 http://maxima.sourceforge.net
Using Lisp GNU Common Lisp (GCL) GCL 2.6.7 (aka GCL)
(%i1) display2d:false$
(%i2) x: -sqrt(2)/2;
(%o2) -sqrt(2)/2
(%i3) y: sqrt(2)/-2;
(%o3) -sqrt(2)/2
(%i4) map(ratsimp,[x,y]);
(%o4) [-sqrt(2)/2,-sqrt(2)/2]
(%i5) :lisp $x
((MTIMES SIMP) ((RAT SIMP) -1 2) ((MEXPT SIMP) 2 ((RAT SIMP) 1 2)))
(%i5) :lisp $y
((MTIMES SIMP) ((RAT SIMP) -1 2) ((MEXPT SIMP) 2 ((RAT SIMP) 1 2)))
Maxima 5.10.0: http://maxima.sourceforge.net
Using Lisp GNU Common Lisp (GCL) GCL 2.6.8 (aka GCL)
(%i1) display2d:false$
(%i2) x: -sqrt(2)/2;
(%o2) -2^-(1/2)
(%i3) y: sqrt(2)/-2;
(%o3) -sqrt(2)/2
(%i4) map(ratsimp,[x,y]);
(%o4) [-1/sqrt(2),-sqrt(2)/2]
(%i5) :lisp $x
((MTIMES SIMP) -1 ((MEXPT) 2 ((RAT SIMP) -1 2)))
(%i5) :lisp $y
((MTIMES SIMP) ((RAT SIMP) -1 2) ((MEXPT SIMP) 2 ((RAT SIMP) 1 2)))
Richard,
you are right, sqrt(2)/-2 is bizarre. I just tried to figure out, why my rotation matrices (see my
previous posting) show different results.
Regards
Volker van Nek
Am 18 Aug 2008 um 22:58 hat Richard Fateman geschrieben:
> Macsyma provides the same answer, -sqrt(2)/2 for both x and y.
>
> the simplification to 1/sqrt(2) is, I think, not something that ratsimp
> should do.
> The occurrence of an expression without a simp flag is wrong. If someone
> can run
> a very old version of maxima, it might help narrow the change time.
>
> Also note that parsing sqrt(2)/-2 is kind of bizarre.
> ma
> RJF
>
> > -----Original Message-----
> > From: maxima-bounces at math.utexas.edu
> > [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Robert Dodier
> > Sent: Monday, August 18, 2008 8:28 PM
> > To: van Nek
> > Cc: Maxima at math.utexas.edu
> > Subject: Re: [Maxima] sqrt(2)/2
> >
> > On 8/18/08, van Nek <van.nek at arcor.de> wrote:
> >
> > > I think there shouldn't be a difference. The second mexpt
> > has a simp
> > > flag. If I understand right this prevents y from being simplified.
> >
> > I don't know what is the right answer here. However I hope that
> > the 2 or 3 people who do know will comment. Otherwise I might
> > get inspired to try to figure it out and change it myself.
> >
> > If I'm not mistaken the simplification of radicals was modified
> > in the recent past (not more than 2 years ago). I forget what
> > was at issue then, and what changes were made; but maybe
> > before making further changes it would be useful to review.
> >
> > best
> >
> > Robert Dodier
> > _______________________________________________
> > Maxima mailing list
> > Maxima at math.utexas.edu
> > http://www.math.utexas.edu/mailman/listinfo/maxima
> >
>
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