module Alea.Random where

import System.Random
import Alea.List

-- Get n random numbers from the list ys
randPick :: (Eq a, RandomGen g) => [a] -> Int -> g -> ([a], g)
randPick [] _ gen = ([], gen)
randPick _ 0  gen = ([], gen)
randPick ys n gen = (x : xs', gen'')
	where
		(randIndex, gen') = randomR (0, length ys - 1) gen
		(x, xs) = removeAt randIndex ys
		(xs', gen'') = randPick xs (n-1) gen'

-- Generate k random number in the range [0, n)
randWords :: Int -> Int -> IO [Int]
randWords n k = getStdRandom (randPick [0..n] k)