{"id":817,"date":"2014-12-17T06:00:06","date_gmt":"2014-12-17T04:00:06","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=817"},"modified":"2014-12-27T21:04:53","modified_gmt":"2014-12-27T19:04:53","slug":"elementos-adicionales","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/elementos-adicionales\/","title":{"rendered":"Elementos adicionales"},"content":{"rendered":"<h4>Enunciado<\/h4>\n<pre lang=\"text\">\n-- Definir la funci\u00f3n\n--    adicionales :: Ord a => Int -> [a] -> [a] -> [a]\n-- tal que (adicionales n xs ys) es la lista de los n elementos de xs\n-- que no pertenecen a ys (se supone que las listas xs e ys est\u00e1n\n-- ordenadas y que pueden ser infinitas). Por ejemplo, \n--    adicionales 0 [1,3]   [1,3]                  ==  []\n--    adicionales 1 [1,3]   [1]                    ==  [3]\n--    adicionales 2 [1,3,5] [1]                    ==  [3,5]\n--    adicionales 2 [1,3,5,7,9] [1,5,7]            ==  [3,9]\n--    adicionales 2 ([1,3,5]++[7..]) ([1]++[7..])  ==  [3,5]\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\n-- 1\u00aa definici\u00f3n (por recursi\u00f3n)\nadicionales1 :: Ord a => Int -> [a] -> [a] -> [a]\nadicionales1 0 _  _  = []\nadicionales1 _ xs [] = xs\nadicionales1 n (x:xs) (y:ys) \n    | x <  y    = x : adicionales1 (n-1) xs (y:ys)\n    | x == y    = adicionales1 n xs ys\n    | otherwise = adicionales1 n (x:xs) ys\n\n-- 2\u00aa definici\u00f3n (por comprensi\u00f3n):\nadicionales2 :: Ord a => Int -> [a] -> [a] -> [a]\nadicionales2 n xs ys =\n    take n [x | x <- xs, x `noPertenece` ys]\n\n-- (noPertenece x ys) se verifica si x no pertenece a la lista ordenada \n-- (posiblemente infinita ys). Por ejemplo.\n--    noPertenece 2 [3,5]    ==  True\n--    noPertenece 4 [3,5]    ==  True\n--    noPertenece 7 [3,5]    ==  True\n--    noPertenece 4 [3,5..]  ==  True\nnoPertenece :: Ord a => a -> [a] -> Bool\nnoPertenece x ys = null zs || head zs \/= x\n    where zs = dropWhile (<x) ys\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Enunciado &#8212; Definir la funci\u00f3n &#8212; adicionales :: Ord a => Int -> [a] -> [a] -> [a] &#8212; tal que (adicionales n xs ys) es la lista de los n elementos de xs &#8212; que no pertenecen a ys (se supone que las listas xs e ys est\u00e1n &#8212; ordenadas y que pueden ser&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"footnotes":"","_jetpack_memberships_contains_paid_content":false},"categories":[4],"tags":[8,59,71,141,11,6,47],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/817"}],"collection":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/comments?post=817"}],"version-history":[{"count":3,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/817\/revisions"}],"predecessor-version":[{"id":881,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/817\/revisions\/881"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=817"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=817"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=817"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}