Fedotova hw4

proj4/app/Main.hs

@@ -3,133 +3,28 @@ module Main where
 import Streaming as S
 import qualified Streaming.Prelude as S
 
-import TheLens ()
-
--- Вывести на экран список list
--- в cols столбцов (например,
--- после каждого числа вывести
--- знак табуляции) и вернуть
--- сумму элементов списка
---
--- > sumAndTabulate 3 [1..10]
--- >
--- >    1       2       3
--- >    4       5       6
--- >    7       8       9
--- >    10
--- >
--- > 55
 sumAndTabulate :: Int -> [Int] -> IO Int
-sumAndTabulate cols list = error "Write me!"
-
-
--- -- Свободная монада - на одном из следующих занятий
--- data S f m r
---   = Elem (f (S f m r)) -- "чистый" элемент e и данные дальше
---   | Act (m (S f m r))  -- данные из действия (в монаде m)
---   | Res r              -- результат r
-
-stS :: Int
-    -> Stream (Of Int) IO Int
-    -> IO Int
-stS cols = fmap S.fst' .
-  S.sum .
-  S.mapM_ (liftIO . putStrLn) .
-  tabS 3 .
-  S.copy
-
--- Получение стрима из нужных строк
-tabS :: Monad m
-     => Int
-     -> Stream (Of Int) m r
-     -> Stream (Of String) m r
-tabS cols ints = S.mapsM S.mconcat $
-                 S.chunksOf cols $
-                 S.map addTab ints
-  where addTab x = show x ++ "\t"
-
--- Вывод на экран
-outTabS :: Int
-        -> Stream (Of Int) IO ()
-        -> IO ()
-outTabS cols = S.mapM_ putStrLn .
-               tabS cols
-
---------------------------------------
 
-type Lens f s t a b
-  = (a -> f b) -- функция модификации поля
-  -> s         -- старый объект
-  -> f t       -- новый объект
-type Lens' f s a = Lens f s s a a
+sumAndTabulate cols list = do
+   sumAndTabulate' cols list 1
+   putStrLn "\n"
+   return $ sum list
 
-ix :: Functor f => Int -> Lens' f [a] a
-ix k = go k
-  where
-    go 0 f (x:xs) = (:xs) <$> f x
-    go k f (x:xs) = (x:) <$> go (k-1) f xs
+sumAndTabulate' cols (x : xs) cur
+ | null xs = printNum x
+ | cols == cur = do
+   printLnNum x
+   sumAndTabulate' cols xs 1
+ | otherwise = do
+   printNum x
+   sumAndTabulate' cols xs (cur + 1)
 
-_1 :: Functor f => Lens f (a,b) (c,b) a c
-_1 f (a,b) = (\x -> (x,b)) <$> f a
+printNum x = putStr $ "\t" ++ show x
 
-_2 :: Functor f => Lens f (a,b) (a,d) b d
-_2 f (a,b) = (\x -> (a,x)) <$> f b
-
-ex1 = (ix 4) Identity [1..10]
-ex2 = (ix 4) (const $ Identity 101) [1..10]
-ex3 = (ix 4) (\x -> [101..104]) [1..10]
-ex4 = (ix 4) (\x -> (x,x)) [1..10]
-ex5 = _1 (const $ Identity 789) (123,456)
-ex6 = _1 (const $ Identity "ads") (123,456)
-ex7 = _2 (Identity . show) (123,456)
-ex8 = _2 (\x -> [show x, show $ x+1]) (123,456)
-ex9 = (_1 . _2) (const $ Identity "x") ((1,2),3)
-
-
-
-
-{-------------------
-*Main> ((1,[3::Int,4,5]),(2,3))^._2._2
-3
-*Main> ((1,[3::Int,4,5]),(2,3)) & _2._2 .~ "asd"
-((1,[3,4,5]),(2,"asd"))
-*Main> ((1,[3::Int,4,5]),(2,3)) & _2._2 .~ (123,321)
-((1,[3,4,5]),(2,(123,321)))
-*Main> ((1,[3::Int,4,5]),(2,3)) ^. _2
-(2,3)
-*Main> ((1,[3::Int,4,5]),(2,3)) & _2 %~ (\(a,b) -> (a,b,123))
-((1,[3,4,5]),(2,3,123))
-*Main> ((1,[3::Int,4,5]),(2,3)) ^. _1 . _2
-[3,4,5]
-*Main> ((1,[3::Int,4,5]),(2,3)) ^? _1 . _2 . ix 5
-Nothing
-*Main> ((1,[3::Int,4,5]),(2,3)) ^? _1 . _2 . ix 1
-Just 4
-*Main> ((1,[3::Int,4,5]),(2,3)) ^.. _1 . _2 . ix 1
-[4]
-*Main> Right 123 :: Either String Int
-Right 123
-*Main> let ea = Right 123 :: Either String Int
-*Main> ea ^? _Left
-Nothing
-*Main> ea ^? _Right
-Just 123
-*Main> ea & _Right .~ 124
-Right 124
-*Main> ea & _Left .~ 124
-Right 123
-*Main> ea & _Left .~ "123"
-Right 123
-*Main> ea & _Left %~ ("f" ++)
-Right 123
-*Main> let eb = Left "asdasd"
-*Main> eb & _Left %~ ("f" ++)
-Left "fasdasd"
-*Main> ea & _Left %~ ("f" ++)
-Right 123
-*Main> ea & _Left %~ ("f" ++)
-Right 123
-------------------}
+printLnNum x = putStrLn $ "\t" ++ show x
 
 main :: IO ()
-main = putStrLn "Hello, Haskell!"
+
+main = do
+  sum <- sumAndTabulate 3 [1..10]
+  putStrLn $ "sum: " ++ show sum