Tuple definition and iteration of sets

Hi,

I wonder if someone would like to give a tip or two on these topics...so here goes. :)

1. I want to define a tuple of three sets where one set can possibly be empty. How can I describe this?

2. I wonder how to apply a function to all elements of a set.

3. How can I specify that the legal type of argument to the function 'iterate' is all kind of sets (or eventually a special kind of sets)? That is, how do I specify the type of argument of a function?

Please see the description here: Zippyshare.com

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