[Haskell-cafe] Acquiring a random set of a specific size (w/o dups) from a range of Ints

[Alexander Solla]

On Mon, Jun 13, 2011 at 4:56 PM, michael rice <nowgate at yahoo.com> wrote:

> Is there an (existing) way to select 5 Ints randomly (no duplicates) from a
> population, say 1-20 (inclusive)?
>
> Michael
>

This is as close as I have gotten, but it is only probabilistically true.

take_n_unique_randoms_in_range :: ( Ord random
                                  , Random random
                                  , MonadIO io
                                  ) => Int -> (random, random) -> io
[random]
take_n_unique_randoms_in_range n (a,b) = liftM ((take n) . nub) .
(replicateM (3*n)) . liftIO $ randomRIO (a,b)

I'm going to put making an iteratee-based solution on my agenda.
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