Re: Is it a bug in arithmetic operation, in printf ???

[Matthias Felleisen <matthias@ccs.neu.edu>]

  > Still another question: Is there eventually some possibility to
  > undefine all symbols? If there was, I would not have to kill and
  > restart MzScheme to try out if my program really works. 

You can undefine variables (identifiers), but you can't undefine symbols. 
(Unless Matthew did something behind my back.) 

  > Sometimes it works only because of old definitions that remain in
  > MzScheme but are not part of the editing-buffer anymore. How does
  > DrScheme handle this?

DrScheme was designed to deal with this pitfall (and others). 
It uses a new namespace for every Execute but it keeps the history
of interactions. I have fallen into this pit many times before
DrScheme, and I know people with 30 years of Lisp/Scheme experience who
still do. 

I switched to DrScheme from Emacs, as a die-hard Emacs user (still running
RMAIL under Emacs), many years back. Rarely ever regretted it. But now that
v200 is out, I would never switch back to Emacs for Scheme. Use modules and
be happy. 

-- Matthias, who does everything in Emacs, except for Scheme and laundry