Printing generations using life function

life.hs

@@ -1,5 +1,5 @@
 import Data.List
-data Point = Point Integer Integer deriving (Show, Eq)
+data Point = Point Int Int deriving (Show, Eq)
 
 tick :: [Point] -> [Point]
 tick world = [ cell | cell <- cells_involved_in_this_tick, will_live cell world]
@@ -14,7 +14,7 @@ is_neighbour (Point x1 y1) (Point x2 y2)
             dy = abs (y1-y2)
             is_same_point = x1 == x2 && y1 == y2
 
-count_neighbours :: Point -> [Point] -> Integer
+count_neighbours :: Point -> [Point] -> Int
 count_neighbours _ [] = 0
 count_neighbours pt (x:xs) = 
     let single_neighbour = if is_neighbour pt x then 1 else 0
@@ -35,15 +35,50 @@ neighbours (Point x y) = [(Point (x-1) (y-1)), (Point x (y-1)), (Point (x+1) (y-
                           (Point (x-1) y),                  (Point (x+1) y),
                           (Point (x-1) (y+1)), (Point x (y+1)), (Point (x+1) (y+1))]
 
+life :: Int -> [Point] -> IO()
+life 0 _ = return ()
+life gens world = do
+    putStrLn $ show_world world dimensions
+    life (gens-1) (tick world)
+    where dimensions = world_dimensions world
+
+show_world :: [Point] -> (Point, Point) -> [Char]
+show_world world ((Point startX startY), (Point endX endY)) =
+    lineBreakAt cells_per_row [ show_point p (p `elem` world) | p<-all_points ]
+    where
+        all_points = [(Point x y) | x<-[startX..endX], y<-[startY..endY]]
+        cells_per_row = endX - startX + 1
+
+show_point :: Point -> Bool -> Char
+show_point pt True = 'X'
+show_point pt False = '_'
+
+get_row :: Int -> [Point] -> [Point]
+get_row rowCoord world = [(Point x y) | (Point x y)<-world, y == rowCoord]
+
+world_dimensions :: [Point] -> (Point, Point)
+world_dimensions [] = ((Point 0 0), (Point 0 0))
+world_dimensions cells = ((Point min_x min_y), (Point max_x max_y))
+    where max_x = maximum [ x | (Point x y) <- cells ]
+          min_x = minimum [ x | (Point x y) <- cells ]
+          max_y = maximum [ y | (Point x y) <- cells ]
+          min_y = minimum [ y | (Point x y) <- cells ]
+
 flatten :: [[a]] -> [a]
 flatten [] = []
 flatten (x:xs) = x ++ (flatten xs) 
 
+lineBreakAt :: Int -> [Char] -> [Char]
+lineBreakAt n [] = []
+lineBreakAt n s = take n s ++ "\n" ++ (lineBreakAt n $ drop n s)
+
+
 assert_equal :: Eq a => Show a => a -> a -> IO()
 assert_equal x y
     | x == y = putStrLn "."
     | otherwise = putStrLn ("Expected " ++ show x ++ ", got " ++ show y)
 
+
 main :: IO ()
 main = do  
         assert_equal True (is_neighbour (Point 1 1) (Point 1 2))