Thanks for the support. I made pw.mac in the hope that it would be useful.
Rich
----- Original Message -----
From: "Doug Stewart" <dastew at sympatico.ca>
To: "Richard Hennessy" <rvh2007 at comcast.net>
Cc: "Richard Fateman" <fateman at cs.berkeley.edu>; "Maxima List" <maxima at math.utexas.edu>; "Barton Willis" <willisb at unk.edu>
Sent: Saturday, December 20, 2008 12:09 PM
Subject: Re: [Maxima] pw.mac version 2.3.1
Hi R. Hennessy:
I realy do appreciate all the work that you have done on this!!! Great job.
I will use it in my classes.
Doug Stewart
PS I know that you see some scope creep but this means that what you
have done has got more people interested and they can see that it will
be useful in other areas.
Richard Hennessy wrote:
> Richard,
>
> I was not interested in any case other than linear arguments in the signum() or unit_step() functions when I started work on
> pw.mac.
> The other posibilities are not really in scope for this project. Also my aim was to provide a way to express any piecewise
> function
> in terms of signum() and/or unit_step(). This can be done even with the restriction to linear only arguments. I think if someone
> is concerned with nonlinear arguments then I don't guarantee correct results. That was an enhancement that I knew was unnecessary
> and risky and now I am being criticised for it not working in all cases. That is not my problem as it is out of scope for this
> project. I think I may have allowed some scope creep to occur here. I now have to figure out how to get this back under control.
>
> Rich
>
>
>
> ----- Original Message -----
> From: "Richard Fateman" <fateman at cs.berkeley.edu>
> To: "Richard Hennessy" <rvh2007 at comcast.net>
> Cc: "Barton Willis" <willisb at unk.edu>; "Maxima List" <maxima at math.utexas.edu>
> Sent: Saturday, December 20, 2008 10:29 AM
> Subject: Re: [Maxima] pw.mac version 2.3.1
>
>
> If you want to know how many real roots there are in a polynomial, you
> noticed that there are exact methods in Maxima based on Sturm sequences.
> You also suggested that you are concerned about floating-point numbers
> in the given polynomial. Assume that they are exact, even if presented
> as floats. Again, as you suggest, you can convert them to exact-looking
> rational numbers and then use the exact methods. This is consistent
> with the usual approach in Maxima, which is to say that if you are using
> exact methods and there is a number that appears like
> 0.5, then it is exactly 1/2. Every floating point number can be
> represented exactly as a rational, and if the user does not mean that
> number, then it is the user's problem to find the right way to convey
> the problem exactly to an exact method. It is not Maxima's problem to
> guess how many digits of the user's input should be believed. It should
> believe all of them.
>
>
> If you want to keep the floating-point or bigfloat numbers around, then
> I suggest you just offer to do the whole job numerically and be done
> with it. Use conventional quadrature and sampling. And let someone
> else's program do it.
> RJF
>
>
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