[plt-scheme] behaviour of void?

Matthias Felleisen wrote:

> Tell them not to use void?. Tell them not to cover chapters VII and 
> VIII. Instead have students work on large projects and spend lectures on 
> iterative refinement and re-doing projects. -- Matthias

I'll tell them not to use `void?'. But they're covering some chapter VII 
and VIII material (not in a lot of detail) for the imminent transition 
to Python. We're doing the same in the majors course for the transition 
to C, using a memory model to explain effects. I wasn't going to talk 
about mutable structures in Scheme at all, but other instructors 
suggested that it was better to get a little practice in the friendly 
environment of DrScheme before the cold harsh reality of gcc on the 
command line... --PR