44 lines
1.1 KiB
Haskell
44 lines
1.1 KiB
Haskell
module Util where
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elemSnd :: a -> [(a,b)] -> Bool
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elemSnd a l = any (\(x,_) -> x == a) l
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matchSnd :: a -> (a,b) -> Bool
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matchSnd t (a,_) = a == t
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getFirstMatchNS :: [a] -> (a -> Bool) -> [a]
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getFirstMatchNS l f = unwrapMaybe . (getFirstMatch l f)
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unwrapMaybe :: Maybe a -> a
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unwrapMaybe (Just a) = a
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unwrapMaybe _ = error "Brutal Present: Unwrapped Nothing"
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rmFirstMatch :: [a] -> (a -> Bool) -> [a]
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rmFirstMatch [] _ = []
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rmFirstMatch (l:ls) f
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| f l = ls
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| otherwise = (l : rmFirstMatch ls f)
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unwrapLeft :: Either a b -> a
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unwrapLeft (Left x) = x
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unwrapLeft (Right _) = error "Not a Left value"
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unwrapRight :: Either a b -> b
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unwrapRight (Right x) = x
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unwrapRight (Left _) = error "Not a Right value"
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-- Remove duplicates, stabily
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uniq :: (Eq a) => [a] -> [a]
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uniq x = reverse $ go x []
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where
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go [] al = al
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go (c:cs) al = if (c `elem` al) then (go cs al) else (go cs (c:al))
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-- Return the first item that f returns true for
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getFirstMatch :: [a] -> (a -> Bool) -> Maybe a
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getFirstMatch [] _ = Nothing
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getFirstMatch (l:ls) f
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| f l = Just l
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| otherwise = getFirstMatch ls f
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