[Haskell-cafe] how to select random elements of a Data.Set?

[jwaldmann]

Dear all,

how would I quickly select an element of a Set (as in Data.Set)
uniformly at random? 

Via the API, this can only be done in linear time? (via toList)
If I could access the tree structure, 
then of course it could be logarithmic.

But probably I'd need a weighted selection sooner or later,
and this would require some specific code anyway. Or does it not?

Actually I need a sequence of such selections
(each selected element is deleted immediately).
I don't need all elements 
(so, computing a random permuation might be too much).

J.W.