Extensión de un fichero

5 Comentarios

1. He definido la función de dos maneras distintas : extension y extension2

   Haskell

   extension :: String -> String extension xs | notElem '.' xs = "" | otherwise = extensionAux xs extensionAux (x:xs) | x == '.' && notElem '.' xs = xs | otherwise = extension xs extension2 :: String -> String extension2 xs | notElem '.' xs = "" | otherwise = snd (splitAt (last (posicion '.' xs)) xs) posiciones xs = zip xs [1..length xs - 1] posicion x xs = [b | (a,b) <- posiciones xs, x == a]

   1 2 3 4 5 6 7 8 9 10 11 12 13 14

   extension :: String -> String extension xs | notElem '.' xs = ""              | otherwise      = extensionAux xs   extensionAux (x:xs) | x == '.' && notElem '.' xs = xs                     | otherwise                  = extension xs   extension2 :: String -> String extension2 xs | notElem '.' xs = ""               | otherwise      = snd (splitAt (last (posicion '.' xs)) xs)   posiciones xs = zip xs [1..length xs - 1]   posicion x xs = [b | (a,b) <- posiciones xs, x == a]

   Responder

2. Haskell

   extension :: String -> String extension cs | not (elem '.' cs) = "" | otherwise = [x| (x,y) <- zip cs [0..],y > ultPosicion '.' cs] ultPosicion x xs = last [y | (z,y) <- zip xs [0..], z == x ]

   1 2 3 4 5 6

   extension :: String -> String extension cs     | not (elem '.' cs) = ""     | otherwise         = [x| (x,y) <- zip cs [0..],y > ultPosicion '.' cs]   ultPosicion x xs = last [y | (z,y) <- zip xs [0..], z == x ]

   Responder

   1. Haskell

      extension :: String -> String extension cs | notElem '.' cs = "" | otherwise = [x| (x,y) <- zip cs [0..],y > ultPosicion '.' cs] ultPosicion x xs = last [y | (z,y) <- zip xs [0..], z == x ]

      1 2 3 4 5 6

      extension :: String -> String extension cs     | notElem '.' cs = ""     | otherwise         = [x| (x,y) <- zip cs [0..],y > ultPosicion '.' cs] ultPosicion x xs = last [y | (z,y) <- zip xs [0..], z == x ]

      He simplificado not (elem ‘.’ cs) por notElem ‘.’ cs

      Responder

   2. Haskell

      extension :: String -> String extension cs | notElem '.' cs = "" | otherwise = [x| (x,y) <- zip cs [0..], y > u] where u = last [y | ('.',y) <- zip cs [0..]]

      1 2 3 4

      extension :: String -> String extension cs | notElem '.' cs = ""              | otherwise = [x| (x,y) <- zip cs [0..], y > u]              where u = last [y | ('.',y) <- zip cs [0..]]

      Usando una variable local aumenta considerablemente la eficiencia de la definición.

      Responder

      1. Haskell

         extension :: String -> String extension cs | notElem '.' cs = "" | otherwise = drop u cs where u = last [y | ('.',y) <- zip cs [0..]]

         1 2 3 4

         extension :: String -> String extension cs | notElem '.' cs = ""              | otherwise = drop u cs              where u = last [y | ('.',y) <- zip cs [0..]]

         Más simplificado

         Responder