[plt-scheme] When would you use units rather than classes?

On Fri, Apr 4, 2008 at 10:29 PM, Grant Rettke <grettke at acm.org> wrote:
>  From what I can gather, a module defines its dependencies, and how
>  they are fulfilled, only once. Every time that modules is utilized,
>  its internal bindings are the same.
>
>  Units define their dependencies, but not how they are fulfilled. Every
>  time you utilize a unit, you must satisfy its requirements.

By the way, "from what I can gather" means that I am trying to figure
it out myself :)