{"id":2538,"date":"2016-11-07T06:00:46","date_gmt":"2016-11-07T04:00:46","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=2538"},"modified":"2016-11-14T08:18:10","modified_gmt":"2016-11-14T06:18:10","slug":"primo-anterior","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/primo-anterior\/","title":{"rendered":"Primo anterior"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   primoAnterior :: Integer -> Integer\n<\/pre>\n<p>tal que (primoAnterior n) es el mayor primo menor que n (donde n > 2). Por ejemplo,<\/p>\n<pre lang=\"text\">\n   primoAnterior 10     ==  7\n   primoAnterior 17     ==  13\n   primoAnterior 30     ==  29\n   primoAnterior 2016   ==  2011\n   primoAnterior 15726  ==  15683\n<\/pre>\n<p>Calcular el menor n\u00famero cuya distancia a su primo anterior es mayor que 40.<\/p>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Data.Numbers.Primes ( isPrime\n                           , primes\n                           )\n\n-- 1\u00aa definici\u00f3n\nprimoAnterior1 :: Integer -> Integer\nprimoAnterior1 n =\n  last (takeWhile (<n) primes)\n\n-- 2\u00aa definici\u00f3n\nprimoAnterior2 :: Integer -> Integer\nprimoAnterior2 3 = 2\nprimoAnterior2 n =\n  head [x | x <- [a,a-2..]\n          , isPrime x]\n  where a | even n    = n-1\n          | otherwise = n-2\n\n-- Comparaci\u00f3n de eficiencia  \n--    \u03bb> primoAnterior1 3000000\n--    2999999\n--    (1.80 secs, 1,148,572,848 bytes)\n--    \u03bb> primoAnterior2 3000000\n--    2999999\n--    (0.00 secs, 0 bytes)\n--    \n--    \u03bb> head [n | n <- [3..], n - primoAnterior1 n > 34]\n--    9586\n--    (28.08 secs, 14,396,008,560 bytes)\n--    \u03bb> head [n | n <- [3..], n - primoAnterior2 n > 34]\n--    9586\n--    (1.10 secs, 625,247,632 bytes)\n\n-- El c\u00e1lculo es\n--    \u03bb> head [n | n <- [3..], n - primoAnterior2 n > 40]\n--    15724\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n primoAnterior :: Integer -> Integer tal que (primoAnterior n) es el mayor primo menor que n (donde n > 2). Por ejemplo, primoAnterior 10 == 7 primoAnterior 17 == 13 primoAnterior 30 == 29 primoAnterior 2016 == 2011 primoAnterior 15726 == 15683 Calcular el menor n\u00famero cuya distancia a su primo anterior&#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":[8,91,71,174,134,11,173,34],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2538"}],"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=2538"}],"version-history":[{"count":3,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2538\/revisions"}],"predecessor-version":[{"id":2575,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2538\/revisions\/2575"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=2538"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=2538"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=2538"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}