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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