This is a real problem, and only occurs in new versions of maxima like
5.13.0. Radcan works well in versions 5.10, and 5.9.
Yes. My problem is not exactly the one I gave. I just tried to find the real
reason for my problem, and then, found "radcan(x^0.000000001/x^0.00000001
);".
YC
On Nov 28, 2007 8:10 AM, Richard Fateman <fateman at cs.berkeley.edu> wrote:
> This problem doesn't show up on wxmaxima (GCL).
>
>
> Radcan works in EXACT algebraic extensions (roots of integer polynomials).
> a floating point number as a power is certainly peculiar. and radcan
> (really
> ratsimp and the CRE package)
> tries to make sense of this by changing the input to 1/(x)^(1/111111111).
>
> Did this come up in a real problem,
> or are you just trying to see how far the envelope goes for trying to make
> sense from marginal cases?
> RJF
>
>
>
>
> > -----Original Message-----
> > From: maxima-bounces at math.utexas.edu
> > [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Robert Dodier
> > Sent: Tuesday, November 27, 2007 9:32 PM
> > To: Zou Yuan-Chuan; Andreas Eder
> > Cc: maxima at math.utexas.edu
> > Subject: Re: [Maxima] radcan error
> >
> > On 11/27/07, Zou Yuan-Chuan <yuanchuan at gmail.com> wrote:
> >
> > > I don't know whether it is a real bug, but...
> >
> > Yep, it's a real bug, all right.
> >
> > > (%i301) radcan(x^0.000000001/x^0.00000001);
> > >
> > > `rat' replaced -9.0E-9 by -1/111111111 = -9.000000008999999E-9
> > > Exponent out of range
> >
> > A lot of the stuff to work on integers was originally coded to
> > exploit faster operations for fixed-size integers, which means the
> > code could fail if some integers turn out to be too large (and the
> > definition of "too large" depends on the Lisp implementation).
> > I believe most of that code has been cut out, and that error message
> > is a left-over: there is a test to detemine if 111111111 is a
> > "big number" (via a function named BIGNUMP), and for at least
> > one Lisp implementation, it is. I suspect that test (in PCOEFADD)
> > can be cut out, without harm.
> >
> > If the above error message is causing trouble for you, you might
> > redefine PCOEFADD (from src/rat3a.lisp) as follows.
> >
> > (defmfun pcoefadd (e c x)
> > (cond ((pzerop c) x)
> > (t (cons e (cons c x)))))
> >
> > There are still some other calls to BIGNUMP. Maybe some or all
> > of those calls could be cut out. Maybe Andreas Eder can weigh
> > in on this since he spent some time revising the fixnum code.
> >
> > Hope this helps,
> >
> > Robert
> > _______________________________________________
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> >
>
>