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58 lines
1.2 KiB
58 lines
1.2 KiB
7 years ago
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module ReaderPractice where
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import Control.Applicative
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import Data.Maybe
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x :: [Integer]
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x = [1, 2, 3]
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y :: [Integer]
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y = [4, 5, 6]
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z :: [Integer]
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z = [7, 8, 9]
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xs :: Maybe Integer
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xs = lookup 3 $ zip x y
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ys :: Maybe Integer
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ys = lookup 6 $ zip y z
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zs :: Maybe Integer
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zs = lookup 4 $ zip x y
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z' :: Integer -> Maybe Integer
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z' n = lookup n $ zip x z
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x1 :: Maybe (Integer, Integer)
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x1 = liftA2 (,) xs ys
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x2 :: Maybe (Integer, Integer)
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x2 = liftA2 (,) ys zs
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x3 :: Integer -> (Maybe Integer, Maybe Integer)
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x3 = liftA2 (,) z' z'
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summed :: Num c => (c, c) -> c
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summed = uncurry (+)
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bolt :: Integer -> Bool
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bolt = liftA2 (&&) (>3) (<8)
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sequA :: Integral a => a -> [Bool]
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sequA m = sequenceA [(>3), (<8), even] m
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s' :: Maybe Integer
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s' = summed <$> ((,) <$> xs <*> ys)
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main :: IO ()
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main = do
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-- print $ sequenceA [Just (3 :: Integer), Just 2, Just 1]
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-- print $ sequenceA [x, y]
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-- print $ sequenceA [xs, ys]
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-- print $ summed <$> ((,) <$> xs <*> ys)
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-- print $ fmap summed ((,) <$> xs <*> zs)
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-- print $ bolt 7
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-- print $ fmap bolt z
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print $ and $ sequA (7 :: Integer)
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print $ sequA $ fromMaybe 0 s'
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print $ bolt $ fromMaybe 0 ys
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