{"id":1920,"date":"2015-12-29T06:00:54","date_gmt":"2015-12-29T04:00:54","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=1920"},"modified":"2016-05-01T20:08:43","modified_gmt":"2016-05-01T18:08:43","slug":"reconocimiento-de-anterior","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/reconocimiento-de-anterior\/","title":{"rendered":"Reconocimiento de anterior"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   esAnterior :: Eq a => [a] -> a -> a -> Bool\n<\/pre>\n<p>tal que (esAnterior xs y z) se verifica si y ocurre en xs antes que z (que puede no pertenecer a xs). Por ejemplo,<\/p>\n<pre lang=\"text\">\n   esAnterior [1,3,7,2] 3 2  ==  True\n   esAnterior [1,3,7,2] 3 1  ==  False\n   esAnterior [1,3,7,2] 3 5  ==  True\n   esAnterior [1,3,7,2] 5 3  ==  False\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\n-- 1\u00aa definici\u00f3n (por recursi\u00f3n)\nesAnterior1 :: Eq a => [a] -> a -> a -> Bool\nesAnterior1 [] _ _     = False\nesAnterior1 (x:xs) y z = x \/= z && (x == y || esAnterior1 xs y z) \n\n-- 2\u00aa definici\u00f3n\nesAnterior2 :: Eq a => [a] -> a -> a -> Bool\nesAnterior2 xs y z = z `notElem` (takeWhile (\/=y) xs)\n\n-- Comparaci\u00f3n de eficiencia\n--    \u03bb> let n = 1000000 in esAnterior1 [1..n] (n-1) n\n--    True\n--    (2.19 secs, 384,717,008 bytes)\n--    \u03bb> let n = 1000000 in esAnterior2 [1..n] (n-1) n\n--    True\n--    (0.34 secs, 135,479,936 bytes)\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n esAnterior :: Eq a => [a] -> a -> a -> Bool tal que (esAnterior xs y z) se verifica si y ocurre en xs antes que z (que puede no pertenecer a xs). Por ejemplo, esAnterior [1,3,7,2] 3 2 == True esAnterior [1,3,7,2] 3 1 == False esAnterior [1,3,7,2] 3 5&#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":[5],"tags":[27,11,6,34],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/1920"}],"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=1920"}],"version-history":[{"count":3,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/1920\/revisions"}],"predecessor-version":[{"id":1958,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/1920\/revisions\/1958"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=1920"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=1920"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=1920"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}