Ordenación según una función

4 Comentarios

1. Haskell

   import Data.List (sort, sortBy) import Test.QuickCheck (quickCheck) ordenaSegun :: Ord b => (a -> b) -> [a] -> [a] ordenaSegun f = sortBy (\x y -> compare (f x) (f y)) -- Sin sortBy ordenaSegun2 :: Ord b => (a -> b) -> [a] -> [a] ordenaSegun2 f xs = map ((xs!!) . snd) (sort (zip (map f xs) [0..])) prop_ordenaSegun :: Ord a => [a] -> Bool prop_ordenaSegun xs = ordenaSegun id xs == sort xs

   1 2 3 4 5 6 7 8 9 10 11 12

   import Data.List (sort, sortBy) import Test.QuickCheck (quickCheck)   ordenaSegun :: Ord b => (a -> b) -> [a] -> [a] ordenaSegun f = sortBy (\x y -> compare (f x) (f y)) -- Sin sortBy ordenaSegun2 :: Ord b => (a -> b) -> [a] -> [a] ordenaSegun2 f xs = map ((xs!!) . snd) (sort (zip (map f xs) [0..])) prop_ordenaSegun :: Ord a => [a] -> Bool prop_ordenaSegun xs = ordenaSegun id xs == sort xs

   Responder

   1. Data.Ord.comparing es justo la funcion usada en el primero que quedaria simplemente

      Haskell

      ordenaSegun = sortBy . comparing

      1	ordenaSegun = sortBy . comparing

      Responder

2. Haskell

   -- Sin usar sort ordenaSegun f xs = [xs !! (x-1) | x <- segundoElemento f xs] segundoElemento f xs = [y | (x,y) <- ordenaFuncionAplicada f xs] ordenaFuncionAplicada f xs = ordena [(x,y) | (x,y) <- zip (aplicaFuncion f xs) [1..]] aplicaFuncion f xs = [f x| x <- xs] ordena [] = [] ordena (x:xs) = (ordena (menores x xs)) ++ [x] ++ (ordena (mayores x xs)) mayores x xs = [y |y <- xs, y > x] menores x xs = [y | y <- xs, y < x] prop_ordenaSegun xs = ordenaSegun id xs == sort xs

   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

   -- Sin usar sort ordenaSegun f xs = [xs !! (x-1) | x <- segundoElemento f xs]   segundoElemento f xs = [y | (x,y) <- ordenaFuncionAplicada f xs]   ordenaFuncionAplicada f xs =     ordena [(x,y) | (x,y) <- zip (aplicaFuncion f xs) [1..]]   aplicaFuncion f xs = [f x| x <- xs]   ordena [] = [] ordena (x:xs) = (ordena (menores x xs)) ++ [x] ++ (ordena (mayores x xs)) mayores x xs = [y |y <- xs, y > x]   menores x xs = [y | y <- xs, y < x] prop_ordenaSegun xs = ordenaSegun id xs == sort xs

   Responder

3. ordenaSegun :: Ord b => (a -> b) -> [a] -> [a] ordenaSegun f xs = [x | (x,y) <- ordenaPares (zip xs (map f xs))] ordenaPares [] = [] ordenaPares (x:xs) = (ordenaPares (menores x xs)) ++ [x] ++ (ordenaPares (mayores x xs)) mayores x xs = [y | y <- xs, snd y >= snd x] menores x xs = [y | y <- xs, snd y < snd x] prop_ordenaSegun :: Ord a => [a] -> Bool prop_ordenaSegun xs = sort xs == ordenaSegun id xs

   1 2 3 4 5 6 7 8 9 10 11 12 13

   ordenaSegun :: Ord b => (a -> b) -> [a] -> [a] ordenaSegun f xs = [x | (x,y) <- ordenaPares (zip xs (map f xs))]   ordenaPares []     = [] ordenaPares (x:xs) =     (ordenaPares (menores x xs)) ++ [x] ++ (ordenaPares (mayores x xs))   mayores x xs = [y | y <- xs, snd y >= snd x]   menores x xs = [y | y <- xs, snd y <  snd x]   prop_ordenaSegun :: Ord a => [a] -> Bool prop_ordenaSegun xs = sort xs == ordenaSegun id xs

   Responder