División según una propiedad

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1. Haskell

   divideSegun p xs = eliminaVacio p (agrupaPropiedad p xs) agrupaPropiedad p [] = [[]] agrupaPropiedad p xs | not (null (primeraLista p xs)) = [primeraLista p xs] ++ agrupaPropiedad p (xs \\ (primeraLista p xs)) | otherwise = [primeraLista p xs] ++ agrupaPropiedad p (tail (xs \\ (primeraLista p xs))) primeraLista p [] = [] primeraLista p (x:xs) | not (p x) = [x] ++ primeraLista p xs | otherwise = [] eliminaVacio p [] = [] eliminaVacio p (xs:xss) | null xs = eliminaVacio p xss | otherwise = [xs] ++ eliminaVacio p xss

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   divideSegun p xs = eliminaVacio p (agrupaPropiedad p xs)   agrupaPropiedad p [] = [[]] agrupaPropiedad p xs     | not (null (primeraLista p xs)) =         [primeraLista p xs] ++         agrupaPropiedad p (xs \\ (primeraLista p xs))     | otherwise =         [primeraLista p xs] ++         agrupaPropiedad p (tail (xs \\ (primeraLista p xs)))   primeraLista p [] = [] primeraLista p (x:xs) | not (p x) = [x] ++ primeraLista p xs                       | otherwise = []    eliminaVacio p [] = [] eliminaVacio p (xs:xss) | null xs   = eliminaVacio p xss                         | otherwise = [xs] ++ eliminaVacio p xss

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2. Con Data.List.Split y sus combinadores queda mas elegante

   Haskell

   divideSegun :: (a -> Bool) -> [a] -> [[a]] divideSegun _ [] = [] divideSegun p xs = yz : divideSegun p nxt where (yz,zs) = break p xs nxt = dropWhile p zs divideSegun2 :: (a -> Bool) -> [a] -> [[a]] divideSegun2 = split . dropBlanks . dropDelims . whenElt

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   divideSegun :: (a -> Bool) -> [a] -> [[a]] divideSegun _ [] = [] divideSegun p xs = yz : divideSegun p nxt    where (yz,zs) = break p xs          nxt = dropWhile p zs            divideSegun2 :: (a -> Bool) -> [a] -> [[a]] divideSegun2 = split . dropBlanks . dropDelims . whenElt

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3. Haskell

   import Test.QuickCheck divideSegun :: (a -> Bool) -> [a] -> [[a]] divideSegun _ [] = [] divideSegun p (x:xs) | p x = divideSegun p xs | otherwise = (x : takeWhile (not . p) xs) : divideSegun p (dropWhile (not . p) xs) prop_divideSegun :: [Int] -> Bool prop_divideSegun xs = filter odd xs == concat (divideSegun even xs) -- La comprobación es -- λ> quickCheck prop_divideSegun -- +++ OK, passed 100 tests

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   import Test.QuickCheck   divideSegun :: (a -> Bool) -> [a] -> [[a]] divideSegun  _ []     = [] divideSegun p (x:xs) | p x       = divideSegun p xs                      | otherwise = (x : takeWhile (not . p) xs) : divideSegun                        p (dropWhile (not . p) xs)   prop_divideSegun :: [Int] -> Bool prop_divideSegun xs = filter odd xs == concat (divideSegun even xs)   -- La comprobación es --    λ> quickCheck prop_divideSegun --    +++ OK, passed 100 tests

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