{"id":2038,"date":"2016-01-29T06:00:55","date_gmt":"2016-01-29T04:00:55","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=2038"},"modified":"2016-02-05T07:23:47","modified_gmt":"2016-02-05T05:23:47","slug":"agrupamiento-por-propiedad","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/agrupamiento-por-propiedad\/","title":{"rendered":"Agrupamiento por propiedad"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   agrupa :: (a -> Bool) -> [a] -> [[a]]\n<\/pre>\n<p>tal que (agrupa p xs) es la lista obtenida separando los elementos consecutivos de xs que verifican la propiedad p de los que no la verifican. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   agrupa odd   [1,2,0,4,9,6,4,5,7,2]  ==  [[1],[2,0,4],[9],[6,4],[5,7],[2]]\n   agrupa even  [1,2,0,4,9,6,4,5,7,2]  ==  [[],[1],[2,0,4],[9],[6,4],[5,7],[2]]\n   agrupa (> 4) [1,2,0,4,9,6,4,5,7,2]  ==  [[],[1,2,0,4],[9,6],[4],[5,7],[2]]\n   agrupa (< 4) [1,2,0,4,9,6,4,5,7,2]  ==  [[1,2,0],[4,9,6,4,5,7],[2]]\n<\/pre>\n<p>Comprobar con QuickCheck que para cualquier propiedad p y cualquier lista xs, la concatenaci\u00f3n de (agrupa p xs) es xs; es decir,<\/p>\n<pre lang=\"text\">\n   prop_agrupa :: Blind (Int -> Bool) -> [Int] -> Bool\n   prop_agrupa (Blind p) xs =\n       concat (agrupa1 p xs) == xs\n<\/pre>\n<p><strong>Nota<\/strong>. Usar la librer\u00eda <a href=\"http:\/\/bit.ly\/1PDu2zO\">Test.QuickCheck.Modifiers<\/a>.<\/p>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Test.QuickCheck\nimport Test.QuickCheck.Modifiers\n\n-- 1\u00aa soluci\u00f3n\n-- ===========\n\nagrupa1 :: (a -> Bool) -> [a] -> [[a]]\nagrupa1 p [] = []\nagrupa1 p xs = takeWhile p xs : agrupa1 (not . p) (dropWhile p xs)\n\n-- 2\u00aa soluci\u00f3n\n-- ===========\n\nagrupa2 :: (a -> Bool) -> [a] -> [[a]]\nagrupa2 p [] = []\nagrupa2 p xs = ys : agrupa2 (not . p) zs\n    where (ys,zs) = span p xs\n\n-- Propiedad\n-- =========\n\n-- La propiedad es\nprop_agrupa :: Blind (Int -> Bool) -> [Int] -> Bool\nprop_agrupa (Blind p) xs =\n    concat (agrupa1 p xs) == xs\n\n-- La comprobaci\u00f3n es\n--    \u03bb> quickCheck prop_agrupa\n--    +++ OK, passed 100 tests.\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n agrupa :: (a -> Bool) -> [a] -> [[a]] tal que (agrupa p xs) es la lista obtenida separando los elementos consecutivos de xs que verifican la propiedad p de los que no la verifican. Por ejemplo, agrupa odd [1,2,0,4,9,6,4,5,7,2] == [[1],[2,0,4],[9],[6,4],[5,7],[2]] agrupa even [1,2,0,4,9,6,4,5,7,2] == [[],[1],[2,0,4],[9],[6,4],[5,7],[2]] agrupa (> 4) [1,2,0,4,9,6,4,5,7,2] ==&#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":[11,6],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2038"}],"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=2038"}],"version-history":[{"count":6,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2038\/revisions"}],"predecessor-version":[{"id":2083,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/2038\/revisions\/2083"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=2038"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=2038"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=2038"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}