fixpoint + dynamic programming implementation of levenshtein distance

lev.hs

{-# LANGUAGE MultiWayIf #-}
{-# LANGUAGE TupleSections #-}

{-# HLINT ignore "Redundant multi-way if" #-}

import Control.Monad.Fix (fix)
import Data.Array (Array, array)
import qualified Data.Array as A

levCachedArray :: Eq a => [a] -> [a] -> Int
levCachedArray xs ys =
  let bs@(bx, by) = (length xs, length ys)
   in (A.! (0, 0)) $ fix $ \a ->
        Data.Array.array ((0, 0), bs) $
          [((x, by), bx - x) | x <- [0 .. bx]]
            <> [((bx, y), by - y) | y <- [0 .. by]]
            <> do
              (nx, x) <- zip [0 ..] xs
              (ny, y) <- zip [0 ..] ys
              pure $
                ((nx, ny),) $
                  if
                      | x == y -> a A.! (succ nx, succ ny)
                      | otherwise -> 1 + minimum ((a A.!) <$> [(succ nx, succ ny), (nx, succ ny), (succ nx, ny)])