minesweeper kata in haskell, no output

minesweeper.hs

import qualified Data.Map as Map
import Control.Monad


main :: IO ()
main = processOneField


processOneField :: IO ()
processOneField = do
  [n, m] <- (map read . words) <$> getLine :: IO [Int]
  when ((n, m) /= (0, 0)) $ doProcessOneField n m


doProcessOneField :: Int -> Int -> IO ()
doProcessOneField n m = do
  arena <- replicateM n getLine
  let coords = [ (i, j) | i <- [0..n-1], j <- [0..m-1] ]
  let mines = filter ( \ c -> (arena !! fst c) !! snd c == '*' ) coords
  let zeromap = Map.fromList $ map ( \ c -> (c, 0::Int) ) coords
  print $ foldr (f coords) zeromap mines
  processOneField


f :: [(Int, Int)] -> (Int, Int) -> Map.Map (Int, Int) Int -> Map.Map (Int, Int) Int 
f coords (i, j) r = foldr (Map.adjust (+1)) r neighs
  where
    neighs = do
        ii <- [i-1..i+1]
        jj <- [j-1..j+1]
        guard $ (ii, jj) `elem` coords
        return (ii, jj)