51 lines
1.6 KiB
Haskell
51 lines
1.6 KiB
Haskell
module Stream (
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Stream(..)
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) where
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import Data.List (intercalate)
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data Stream a = Stream [(a, Stream a)] deriving Show
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instance Monoid (Stream a) where
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mempty = fromList []
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mappend (Stream []) b = b
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mappend (Stream pairs) b = Stream $ (\(a, stream) -> (a, stream `mappend` b)) <$> pairs
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fromList :: [a] -> Stream a
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fromList [] = Stream []
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fromList (pair:pairs) = Stream [(pair, fromList pairs)]
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infinite :: a -> Stream a
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infinite a = Stream [(a, infinite a)]
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merge :: Eq a => Stream a -> Stream a -> Stream a
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merge (Stream aPairs) (Stream bPairs) = Stream $ foldl mergeOrAdd aPairs bPairs
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where
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openAt _ l [] = (l, [])
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openAt p up l@(x:xs) = if p x then (up, l) else openAt p (x:up) xs
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zipUp ([], l) = l
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zipUp (x:xs, l) = zipUp (xs, x:l)
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mergeOrAdd accumulator (b, bStream) = zipUp $
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case openAt ((== b) . fst) [] accumulator of
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(up, []) -> (up, [(b, bStream)])
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(up, (x, xStream):down) -> (up, (x, merge xStream bStream):down)
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showTree :: Show a => Stream a -> String
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showTree = intercalate "\n" . getLines
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where
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getLines (Stream []) = ["●"]
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getLines (Stream pairs) =
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concat $ (\(a, stream) -> showElem a $ getLines stream) <$> pairs
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showElem :: Show a => a -> [String] -> [String]
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showElem _ [] = []
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showElem a [l] = ["— " ++ show a ++ " —" ++ l]
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showElem a (l:ls) =
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let prefix = "─ " ++ show a ++ " ─┬" in
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let padding = take (length prefix - 1) $ repeat ' ' in
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(prefix ++ l) : (pad padding ls)
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where
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pad _ [] = []
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pad padding [x] = [padding ++ '╰' : x]
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pad padding (x:xs) = (padding ++ '├' : x) : (pad padding xs)
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