Use applicative style

life.hs

@@ -1,3 +1,5 @@
+import Control.Applicative
+import Data.List
 import Matrix
 
 type Cell = Int
@@ -20,9 +22,10 @@ gprint = putStrLn . map replace . show
 
 -- | List of neighbours cells
 near :: Grid -> Pos -> [Cell]
-near g (x, y) = [g ! (x+x', y+y') | x' <- [-1..1],
-                                    y' <- [-1..1],
-                                   (x',y') /= (0,0)]
+near g (x, y) = map state $ neighbours \\ [(0,0)]
+  where
+    neighbours = liftA2 (,) [-1..1] [-1..1]
+    state (x', y') = g ! (x+x', y+y')
 
 -- | Find if a cell will be alive in the next generation
 alive :: Grid -> Pos -> Cell
@@ -30,12 +33,11 @@ alive g p
   | v == 0 && n == 3             = 1
   | v == 1 && (n == 2 || n == 3) = 1
   | otherwise                    = 0
-  where
-    (n, v) = (sum (near g p), g ! p)
+  where (n, v) = (sum (near g p), g ! p)
 
 -- | Compute next generation
 next :: Grid -> Grid
-next g = fmap (alive g) (indeces g)
+next g = alive g <$> indeces g
 
 main :: IO ()
 main = mapM_ gprint (iterate next grid)