There was recently a proposal to add indexing operators to Data.Set.
Until it is accepted, you can simulate Set with Map like this
import Data.Map
type Set a = Map a ()
Data.Map already has indexing operations (e.g. elemAt, deleteAt).
* 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.
_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
-- Roman I. Cheplyaka :: http://ro-che.info/