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src/GameOfLife.hs

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+module GameOfLife (tick) where
+
+type Grid = [[Int]]
+
+-- Maps a function over every element in a grid
+gridMap :: (a -> b) -> [[a]] -> [[b]]
+gridMap f = map (map f)
+
+-- Param 1: The current value of the cell
+-- Param 2: The number of living neighbors
+-- Return value: The next value of the cell
+nextIterHelper :: Int -> Int -> Int
+nextIterHelper 1 2 = 1
+nextIterHelper 1 3 = 1
+nextIterHelper 0 3 = 1
+nextIterHelper _ _ = 0
+
+-- Returns the value of a specific cell in a grid - out-of-bounds is always zero
+cellVal :: Grid -> (Int, Int) -> Int
+cellVal grid (x,y)
+	| x < 0 || y < 0 = 0
+	| y >= length (grid) || x >= length (grid!!0) = 0
+	| otherwise = (grid!!y)!!x
+
+-- Given a tuple (representing the location of a cell),
+-- it returns a list of tuples that are the locations of the neighbors
+neighbors :: (Int, Int) -> [(Int, Int)]
+neighbors (x, y) = [(a,b) | a <- dx, b <- dy, a /= x || b /= y]
+	where 	dx = [x-1..x+1]
+		dy = [y-1..y+1]
+
+-- Predicate - returns whether the cell is alive or not
+isAlive :: Grid -> (Int,Int) -> Bool
+isAlive grid tup = if (cellVal grid tup) == 1 then True else False
+
+-- Filter function that takes a list of indexes in a grid, and only returns the ones
+-- where the cell value is 1
+keepAliveCells :: Grid -> [(Int,Int)] -> [(Int,Int)]
+keepAliveCells grid tups = filter (isAlive grid) tups
+
+-- Returns the number of alive neighbors of the given cell
+numAliveNeighbors :: Grid -> (Int,Int) -> Int
+numAliveNeighbors grid tup = (length . keepAliveCells grid . neighbors) tup
+
+-- Given the grid and the location of a cell, returns the next value of the cell
+nextIter :: Grid -> (Int, Int) -> Int
+nextIter grid tup = nextIterHelper (cellVal grid tup) (numAliveNeighbors grid tup)
+
+-- Returns a grid of all cell indices in the grid
+cellIndices :: Grid -> [[(Int,Int)]]
+cellIndices [[]] = [[]]
+cellIndices grid = [[(x,y) | x <- [0..xdim-1]] | y <- [0..ydim-1]]	
+	where 	xdim = length (grid!!0)
+		ydim = length grid
+
+tick :: Grid -> Grid
+tick [] = []
+tick [[]] = [[]]
+tick grid = gridMap (nextIter grid) (cellIndices grid)