I had suggestions from Stavros & Dan Gildea for improvements to
sign-log--thanks.
This change is checked in--I had some drama getting everything working
on a new computer and new operating system (and new office).
The sign and csign functions are spendy. And the old sign-log was very
slow.
Anytime sign or csign are used in simplifying functions, beware that
sign changes the fact database as it works through an expression. The
clearsign function removes these facts (I think), but clearsign is
mostly only called at the bottom of the read-eval-print loop.
I noticed that sign sometimes calls factor. For something like
signum(x^2-1), it's sad that sign calls factor (not $factor), but
simp-signum doesn't use the factorization: signum(x^2-1) doesn't
simplify to signum(x-1) signum(x+1).
Maybe somebody would like to speed up sign-mplus & sign-mtimes and
improve them algorithmically...
Again, thanks to all that contributed improvements.
--Barton