[plt-scheme] let vs parameterize?

Hi all -

I have a couple of questions on parameterize & parameter objects.  From docs
(
http://download.plt-scheme.org/doc/360/html/mzscheme/mzscheme-Z-H-7.html#node_sec_7.9)
and elsewhere I found that parameter objects differ from regular variables
in such that they have thread-local bindings and can have different values
in thread-specific contexts (similar to Lisp's special variables).  However,
what is unclear to me is when to use it, and when to use let or parameterize
to manipulate parameter objects, etc. specifically:

   - What is the difference between using let vs parameterize?
   - It seems that one can use let to manipulate parameter objects (at
   least scheme doesn't forbid it) - any issues with using it?
   - How do I know whether or not something is a parameter versus a
   variable?
   - Any links to a discussion on variables vs parameters?

Thanks for your help,
yinso

-- 
http://www.yinsochen.com
...continuous learning...
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