Актуальный код в fern.hs

lab2/fern/fern.hs

@@ -1,4 +1,4 @@
-import System.Random (randomRIO)
+import System.Random (StdGen, mkStdGen, randomR)
 
 type Point = (Float, Float)
 
@@ -21,22 +21,20 @@ applyTransformation point random
   | 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
+genNextPoint :: StdGen -> Point -> (Point, StdGen)
+genNextPoint gen point =
+  let (random, newGen) = randomR (0.0, 1.0 :: Float) gen
+  in (applyTransformation point random, newGen)
 
-barnsleyFern :: Point -> Int -> IO [Point]
-barnsleyFern _ 0 = return []
-barnsleyFern startPoint n = do
-  x' <- genNextPoint startPoint
-  xs <- barnsleyFern x' (n - 1)
-  return (startPoint : xs)
+barnsleyFern :: StdGen -> Point -> Int -> [Point]
+barnsleyFern _ _ 0 = []
+barnsleyFern gen startPoint n =
+  let (nextPoint, newGen) = genNextPoint gen startPoint
+  in startPoint : barnsleyFern newGen nextPoint (n - 1)
+
+
+n = 1000
+randomSeed = 17
 
 main :: IO ()
-main = do
-  putStrLn "Укажите количество шагов рекурсии:"
-  input <- getLine
-  let n = read input :: Int
-  fractal <- barnsleyFern (0, 0) n
-  print fractal
+main = print $ barnsleyFern (mkStdGen randomSeed) (0, 0) n

lab2/fern/fern_with_monads.hs

@@ -1,4 +1,6 @@
-import System.Random (StdGen, mkStdGen, randomR)
+-- Не стоит в первой же лабе использовать монады, можно и без них
+
+import System.Random (randomRIO)
 
 type Point = (Float, Float)
 
@@ -21,20 +23,22 @@ applyTransformation point random
   | random < 0.93 = transformation3 point
   | otherwise = transformation4 point
 
-genNextPoint :: StdGen -> Point -> (Point, StdGen)
-genNextPoint gen point =
-  let (random, newGen) = randomR (0.0, 1.0 :: Float) gen
-  in (applyTransformation point random, newGen)
+genNextPoint :: Point -> IO Point
+genNextPoint point = do
+  random <- randomRIO (0.0, 1.0 :: Float)
+  return $ applyTransformation point random
 
-barnsleyFern :: StdGen -> Point -> Int -> [Point]
-barnsleyFern _ _ 0 = []
-barnsleyFern gen startPoint n =
-  let (nextPoint, newGen) = genNextPoint gen startPoint
-  in startPoint : barnsleyFern newGen nextPoint (n - 1)
-
-
-n = 1000
-randomSeed = 17
+barnsleyFern :: Point -> Int -> IO [Point]
+barnsleyFern _ 0 = return []
+barnsleyFern startPoint n = do
+  x' <- genNextPoint startPoint
+  xs <- barnsleyFern x' (n - 1)
+  return (startPoint : xs)
 
 main :: IO ()
-main = print $ barnsleyFern (mkStdGen randomSeed) (0, 0) n
+main = do
+  putStrLn "Укажите количество шагов рекурсии:"
+  input <- getLine
+  let n = read input :: Int
+  fractal <- barnsleyFern (0, 0) n
+  print fractal