On Jan 15, 2007, at 1:57 PM, Jason Mayer wrote:

> Set implements a collection of unordered values with no duplicates.

Yes, that implements sets as defined in math. What you wanted is  
called "multiset"[*], though in my degree I never saw any of those  
even mentioned.

-- fxn

[*] http://mathworld.wolfram.com/Multiset.html