https://wiki.haskell.org/Random_shuffle says:

Here's a variation using the MonadRandom package:

import Control.Monad

import Control.Monad.ST

import Control.Monad.Random

import System.Random

import Data.Array.ST

import GHC.Arr

 

shuffle :: RandomGen g => [a] -> Rand g [a]

shuffle xs = do

    let l = length xs

    rands <- take l `fmap` getRandomRs (0, l-1)

    let ar = runSTArray $ do

        ar <- thawSTArray $ listArray (0, l-1) xs

        forM_ (zip [0..(l-1)] rands) $ \(i, j) -> do

            vi <- readSTArray ar i

            vj <- readSTArray ar j

            writeSTArray ar j vi

            writeSTArray ar i vj

        return ar

    return (elems ar)

 

But this doesn't yield a uniformly-chosen random permutation of its input, because at the i'th step the first `i` elements are not fixed as they are in the other algorithms on that page.

Cheers,

David