99-haskell-problems/Problems 21-28/problem_23.hs

import Data.List (nub)
import System.Random (getStdGen, randomRs)

rndSelect :: [a] -> Int -> IO [a]
rndSelect ls n = do
  gen <- getStdGen
  return $ take n [ls !! m | m <- nub $ randomRs (0, length ls - 1) gen]