Need help -- redefining existing functions (reloading modified source)

Hello,

I'm attempting to figure out a bug fix (#834729).
Toward this end I want to hack on a source file
(plot.lisp) and then reload it and see if the 
modified functions work correctly. I am running 
Maxima 5.9.0 on Clisp 2.29, on RedHat 7.1 (kernel 2.4.2).

However, I find that just reloading the unmodified
file is problematic: with Maxima 5.9.0 (-r1.18 plot.lisp)
if I do load("plot.lisp") then plot(x^3,[x,-1,1]) yields

  *** - THE: (- XEND X) evaluated to the values (2.0), not of type 
LONG-FLOAT

and if I load the most recent CVS version (-r1.32 plot.lisp)
then plot(x^3,[x,-1,1]) yields

  *** - argument to MINUSP should be a real number: NIL

The problem with rev 1.18 is especially puzzling, since
it is the same version that is executed when I just do
plot(x^3,[x,-1,1]) by itself (which does work correctly).

I'm guessing that some functions or macros are getting
redefined in a different namespace or something. 
Can someone comment on this?

How do other people go about testing possible fixes?

I'd rather not rebuild the binary, since it seems
unnecessary, and besides I spent some time trying to
do that and couldn't get it working.

Thanks so much for your help,
Robert Dodier

__________________________________
Do you Yahoo!?
Free Pop-Up Blocker - Get it now
http://companion.yahoo.com/