[plt-scheme] proof checking: a subproblem

Danny Yoo wrote:
> Here's a quick-and-dirty parser for variables, ANDs, and ORs, using the
> parser-tools collection:

Thanks, Danny. That helps, as does the fact that there's an examples 
directory in parser-tools, which I didn't think to look for. I was 
trying to read the documentation through Help Desk and I guess I gave up 
before reaching the end where it says so. --PR