Teachpack setup

[emka@cso.com]

I trying to build what would seem to be a relatively simple teachpack.  I'm
struggling to put all of the pieces together from the examples distributed
with DrScheme and the HelpDesk documentation.  I wondered if someone might
help me get my first one set up?

What I would like to do is add the contents of the trace.ss and compat.ss
libraries to the students standard environment.  In addition to this I
would like to add the following definition:

(define (atom? a) (or (symbol? a) (number? a) (string? a)))

I was able to add only definition of atom? using the following simple
teachpack:

(unit/sig (atom?)
  (import plt:userspace^)
  (define (atom? a) (or (symbol? a)
                        (number? a)
                        (string? a))))

I assume that to pull in and export both the trace and compat libraries I
need to use  a compound signed unit but I'm not sure how to set it up.  I'd
appreciate it if someone could give me a hand.

Thanks,

Eric