Am Sonntag, den 10.07.2011, 07:59 -0500 schrieb Barton Willis:
> When I wrote conjugate.lisp, there was a rudimentary csign (not
> $csign) function. Given the limitations of $sign and the (extreme)
> difficultly in working with code in compar.lisp, your work on $csign
> improved Maxima a great deal--I didn't mean to imply anything negative
> about the function $csign.
Thank you very much for your comment.
> The other day when I gave the sign function object-oriented dispatch,
> I thought (not long) about appending code that would do a better job
> of determining the sign of a single variable polynomial. For a
> polynomial defined on the entire reals, a few lines of code with
> nroots might work, but for a polynomial defined on a subset of the
> reals, it's not easy to determine from the fact database lower and
> upper bounds for a variable (suppose x+y<2 and x-y>5, deduce y <-3/2).
> It would be great if the fact database would maintain bunch of
> derived facts--re-deriving them each time sign is called is too spendy, I
> think.
I like the object-oriented dispatch very much, which gives the
possibility to extend the functionality for functions very easy. At the
moment I am working almost exclusively on the the German translation and
the Maxima manual. But this way, I have collected a lot of ideas to
improve the implemented functions .
Dieter Kaiser