{"id":2709,"date":"2016-12-19T06:00:03","date_gmt":"2016-12-19T04:00:03","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=2709"},"modified":"2016-12-27T08:59:17","modified_gmt":"2016-12-27T06:59:17","slug":"seleccion-por-posicion","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/seleccion-por-posicion\/","title":{"rendered":"Selecci\u00f3n por posici\u00f3n"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   seleccion :: Ord a => [a] -> [Int] -> [a]\n<\/pre>\n<p>tal que (seleccion xs ps) es la lista ordenada de los elementos que ocupan las posiciones indicadas en la lista ps. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   seleccion [6,2,4,7] [2,0]      ==  [4,6]\n   seleccion ['a'..'z'] [0,2..10] ==  \"acegik\"\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Data.List (sort)\n\n-- 1\u00aa definici\u00f3n\nseleccion :: Ord a => [a] -> [Int] -> [a]\nseleccion xs ps =\n  sort [x | (x,n) <- zip xs [0..]\n          , n `elem` ps]\n\n-- 2\u00aa definici\u00f3n\nseleccion2 :: Ord a => [a] -> [Int] -> [a]\nseleccion2 xs = sort . map (xs!!) \n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n seleccion :: Ord a => [a] -> [Int] -> [a] tal que (seleccion xs ps) es la lista ordenada de los elementos que ocupan las posiciones indicadas en la lista ps. Por ejemplo, seleccion [6,2,4,7] [2,0] == [4,6] seleccion [&#8216;a&#8217;..&#8217;z&#8217;] [0,2..10] == \u00abacegik\u00bb Soluciones import Data.List (sort) &#8212; 1\u00aa definici\u00f3n seleccion ::&#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":[8,26,10,11,14,9],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2709"}],"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=2709"}],"version-history":[{"count":3,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2709\/revisions"}],"predecessor-version":[{"id":2754,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2709\/revisions\/2754"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=2709"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=2709"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=2709"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}