Enumerate solutions to the n queens problem

queens.hs

import Control.Applicative (liftA2)
import Data.List (inits, permutations)

queens :: Int -> [[(Int, Int)]]
queens n = filter p $ liftA2 map zip permutations $ take n [0 ..]
    where p x = and $ zipWith f x $ inits x
          f (a, b) = all $ \(c, d) -> abs (a - c) /= abs (b - d)