Definir la funci\u00f3n<\/p>\n
\n duplicaElementos :: [a] -> [a]\n<\/pre>\ntal que (duplicaElementos xs) es la lista obtenida duplicando cada elemento de xs. Por ejemplo,<\/p>\n
\n duplicaElementos1 [3,2,5] == [3,3,2,2,5,5]\n duplicaElementos1 \"Haskell\" == \"HHaasskkeellll\"\n<\/pre>\nSoluciones<\/h4>\n\nimport Test.QuickCheck\n\n-- 1\u00aa soluci\u00f3n\nduplicaElementos1 :: [a] -> [a]\nduplicaElementos1 [] = []\nduplicaElementos1 (x:xs) = x : x : duplicaElementos1 xs\n\n-- 2 soluci\u00f3n\nduplicaElementos2 :: [a] -> [a]\nduplicaElementos2 = foldr (\\x ys -> x:x:ys) []\n\n-- 3\u00aa soluci\u00f3n\nduplicaElementos3 :: [a] -> [a]\nduplicaElementos3 xs = concat [[x,x] | x <- xs]\n\n-- 4\u00aa soluci\u00f3n\nduplicaElementos4 :: [a] -> [a]\nduplicaElementos4 xs = concat (map (replicate 2) xs)\n\n-- 5\u00aa soluci\u00f3n\nduplicaElementos5 :: [a] -> [a]\nduplicaElementos5 = concatMap (replicate 2)\n\n-- 6\u00aa soluci\u00f3n\nduplicaElementos6 :: [a] -> [a]\nduplicaElementos6 = (>>= replicate 2)\n\n-- Equivalencia de las definiciones\n-- ================================\n\n-- La propiedad es\nprop_duplicaElementos :: [Int] -> Bool\nprop_duplicaElementos xs =\n all (== (duplicaElementos1 xs))\n [f xs | f <- [duplicaElementos2,\n duplicaElementos3,\n duplicaElementos4,\n duplicaElementos5,\n duplicaElementos6]]\n\n-- La comprobaci\u00f3n es\n-- \u03bb> quickCheck prop_duplicaElementos\n-- +++ OK, passed 100 tests.\n<\/pre>\n