Running a haskell script without GHC using nix

running-haskell-scripts.md

#!/usr/bin/env nix-shell
#nix-shell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [ mwc-random ])" -i runghc

{-# LANGUAGE ScopedTypeVariables #-}

import System.Random.MWC
import Data.Vector.Unboxed
import Control.Monad.ST

main = do
  vs <- withSystemRandom $
        \(gen::GenST s) -> uniformVector gen 20 :: ST s (Vector Int)
  print vs