{"id":5447,"date":"2020-01-28T05:30:56","date_gmt":"2020-01-28T03:30:56","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=5447"},"modified":"2022-03-26T12:09:25","modified_gmt":"2022-03-26T10:09:25","slug":"primer-elemento-repetido","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/primer-elemento-repetido\/","title":{"rendered":"Primer elemento repetido"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   primerRepetido :: Eq a => [a] -> Maybe a\n<\/pre>\n<p>tal que (primerRepetido xs) es justo el primer elemento repetido de la lista xs o Nothing si no tiene elementos repetidos. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   primerRepetido [3,7,5,7,2]  ==  Just 7\n   primerRepetido [3,9,5,6,2]  ==  Nothing\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nprimerRepetido :: Eq a => [a] -> Maybe a\nprimerRepetido xs = aux xs []\n  where\n    aux [] _                     = Nothing\n    aux (x:xs') ys | x `elem` ys = Just x\n                   | otherwise   = aux xs' (x:ys) \n<\/pre>\n<h4>Otras soluciones<\/h4>\n<ul>\n<li>Se pueden escribir otras soluciones en los comentarios.\n<li>El c\u00f3digo se debe escribir entre una l\u00ednea con &#60;pre lang=\u00bbhaskell\u00bb&#62; y otra con &#60;\/pre&#62;\n<\/ul>\n<h4>Pensamiento<\/h4>\n<blockquote><p>\n\u00ab\u00bfCu\u00e1l es el n\u00facleo central de la ciencia de la computaci\u00f3n? \u00bfQu\u00e9 es lo que lo diferencia de los otros temas con los que se relaciona? \u00bfQu\u00e9 es lo que el hilo de uni\u00f3n que re\u00fane estas ramas dispares en una sola disciplina? Mi respuesta a estas preguntas es simple: es el arte de programar un ordenador. Es el arte de dise\u00f1ar m\u00e9todos eficientes y elegantes para conseguir que un ordenador resuelva problemas, te\u00f3ricos o pr\u00e1cticos,  peque\u00f1os o grandes, simples o complejos. Es el arte de traducir estos dise\u00f1os programas correctos y eficientes.\u00bb <\/p>\n<p><a href=\"https:\/\/en.wikipedia.org\/wiki\/Tony_Hoare\">Tony Hoare<\/a>.\n<\/p><\/blockquote>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n primerRepetido :: Eq a => [a] -> Maybe a tal que (primerRepetido xs) es justo el primer elemento repetido de la lista xs o Nothing si no tiene elementos repetidos. Por ejemplo, primerRepetido [3,7,5,7,2] == Just 7 primerRepetido [3,9,5,6,2] == Nothing Soluciones primerRepetido :: Eq a => [a] -> Maybe a primerRepetido&#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":[500,26,411,6],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/5447"}],"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=5447"}],"version-history":[{"count":6,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/5447\/revisions"}],"predecessor-version":[{"id":5529,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/5447\/revisions\/5529"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=5447"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=5447"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=5447"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}