Data commit

Task/Collections/Haskell/collections-1.hs

@@ -0,0 +1 @@
+[1, 2, 3, 4, 5]

Task/Collections/Haskell/collections-2.hs

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+1 : [2, 3, 4]

Task/Collections/Haskell/collections-3.hs

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+[1, 2] ++ [3, 4]

Task/Collections/Haskell/collections-4.hs

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+concat [[1, 2], [3, 4], [5, 6, 7]]

Task/Collections/Haskell/collections-5.hs

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+import Data.Array (Array, listArray, Ix, (!))
+
+triples :: Array Int (Char, String, String)
+triples =
+  listArray (0, 11) $
+  zip3
+    "鼠牛虎兔龍蛇馬羊猴鸡狗豬" -- 生肖 shengxiao – symbolic animals
+    (words "shǔ niú hǔ tù lóng shé mǎ yáng hóu jī gǒu zhū")
+    (words "rat ox tiger rabbit dragon snake horse goat monkey rooster dog pig")
+
+indexedItem
+  :: Ix i
+  => Array i (Char, String, String) -> i -> String
+indexedItem a n =
+  let (c, w, w1) = a ! n
+  in c : unwords ["\t", w, w1]
+
+main :: IO ()
+main = (putStrLn . unlines) $ indexedItem triples <$> [2, 4, 6]

Task/Collections/Haskell/collections-6.hs

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+import qualified Data.Map as M
+import Data.Maybe (isJust)
+
+mapSample :: M.Map String Int
+mapSample =
+  M.fromList
+    [ ("alpha", 1)
+    , ("beta", 2)
+    , ("gamma", 3)
+    , ("delta", 4)
+    , ("epsilon", 5)
+    , ("zeta", 6)
+    ]
+
+maybeValue :: String -> Maybe Int
+maybeValue = flip M.lookup mapSample
+
+main :: IO ()
+main =
+  print $ sequence $ filter isJust (maybeValue <$> ["beta", "delta", "zeta"])

Task/Collections/Haskell/collections-7.hs

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+import qualified Data.Set as S
+
+setA :: S.Set String
+setA = S.fromList ["alpha", "beta", "gamma", "delta", "epsilon"]
+
+setB :: S.Set String
+setB = S.fromList ["delta", "epsilon", "zeta", "eta", "theta"]
+
+main :: IO ()
+main = (print . S.toList) (S.intersection setA setB)