standard-definitions.hs

map :: (a -> b) -> [a] -> [b]
map f []     = []
map f (x:xs) = f x : map f xs
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zipWith          :: (a->b->c) -> [a]->[b]->[c]
zipWith z (a:as) (b:bs)
                 =  z a b : zipWith z as bs
zipWith _ _ _    =  []
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zip              :: [a] -> [b] -> [(a,b)]
zip              =  zipWith (,)
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unzip            :: [(a,b)] -> ([a],[b])
unzip            =  foldr (\(a,b) ~(as,bs) -> (a:as,b:bs)) ([],[])
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foldl            :: (a -> b -> a) -> a -> [b] -> a
foldl f z []     =  z
foldl f z (x:xs) =  foldl f (f z x) xs
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foldr            :: (a -> b -> b) -> b -> [a] -> b
foldr f z []     =  z
foldr f z (x:xs) =  f x (foldr f z xs)
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take                   :: Int -> [a] -> [a]
take n _      | n <= 0 =  []
take _ []              =  []
take n (x:xs)          =  x : take (n-1) xs
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splitAt                  :: Int -> [a] -> ([a],[a])
splitAt n xs             =  (take n xs, drop n xs)
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