fern

lab2/fern.hs

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+import System.Random (randomRIO)
+
+type Point = (Float, Float)
+
+transformation1 :: Point -> Point
+transformation1 (_, y) = (0, 0.16 * y)
+
+transformation2 :: Point -> Point
+transformation2 (x, y) = (0.85 * x + 0.04 * y, -0.04 * x + 0.85 * y + 1.6)
+
+transformation3 :: Point -> Point
+transformation3 (x, y) = (0.2 * x - 0.26 * y, 0.23 * x + 0.22 * y + 1.6)
+
+transformation4 :: Point -> Point
+transformation4 (x, y) = (-0.15 * x + 0.28 * y, 0.26 * x + 0.24 * y + 0.44)
+
+applyTransformation :: (Ord a, Fractional a) => Point -> a -> Point
+applyTransformation point random
+  | random < 0.01 = transformation1 point
+  | random < 0.86 = transformation2 point
+  | random < 0.93 = transformation3 point
+  | otherwise = transformation4 point
+
+genNextPoint :: Point -> IO Point
+genNextPoint point = do
+  random <- randomRIO (0.0, 1.0 :: Float)
+  return $ applyTransformation point random
+
+barnsleyFern :: Point -> Int -> IO [Point]
+barnsleyFern _ 0 = return []
+barnsleyFern start n = do
+  x' <- genNextPoint start
+  xs <- barnsleyFern x' (n - 1)
+  return (start : xs)
+
+main :: IO ()
+main = do
+  fractal <- barnsleyFern (0, 0) 1000
+  print fractal