{"id":6110,"date":"2021-02-26T06:00:16","date_gmt":"2021-02-26T04:00:16","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=6110"},"modified":"2021-03-05T11:26:55","modified_gmt":"2021-03-05T09:26:55","slug":"eliminaciones-anotadas","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/eliminaciones-anotadas\/","title":{"rendered":"Eliminaciones anotadas"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   eliminaciones :: [a] -> [(a,Int,[a])]\n<\/pre>\n<p>tal que (eliminaciones xs) es la lista de ternas (x,i,zs) tales que x es un elemento de xs, i es la posici\u00f3n de x en xs y zs es la lista de los restantes elementos de xs. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   \u03bb> eliminaciones [5,7,6,5]\n   [(5,0,[7,6,5]),(7,1,[5,6,5]),(6,2,[5,7,5]),(5,3,[5,7,6])]\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Test.QuickCheck (quickCheck)\n\n-- 1\u00aa soluci\u00f3n\neliminaciones :: [a] -> [(a,Int,[a])]\neliminaciones xs = [(z,i,zs) | ((z,zs),i) <- zip (aux xs) [0..]]\n  where aux []       = []\n        aux [x]      = [(x,[])]\n        aux (x:y:zs) = (x,y:zs) : [(v,x:vs) | (v,vs) <- aux (y:zs)]\n\n-- 2\u00aa soluci\u00f3n\neliminaciones2 :: [a] -> [(a,Int,[a])]\neliminaciones2 xs =\n  [(v,i,us++vs) | i <- [0..length xs - 1],\n                  let (us,v:vs) = splitAt i xs]\n\n-- Comprobaci\u00f3n de equivalencia\n-- ============================\n\n-- La propiedad es\nprop_equivalencia :: [Int] -> Bool\nprop_equivalencia xs =\n  eliminaciones xs == eliminaciones2 xs\n\n-- La comprobaci\u00f3n es\n--    \u03bb> quickCheck prop_equivalencia\n--    +++ OK, passed 100 tests.\n<\/pre>\n<h4>Nuevas soluciones<\/h4>\n<ul>\n<li>En los comentarios se pueden escribir nuevas soluciones.\n<li>El c\u00f3digo se debe escribir entre una l\u00ednea con &#60;pre lang=&quot;haskell&quot;&#62; y otra con &#60;\/pre&#62;\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n eliminaciones :: [a] -> [(a,Int,[a])] tal que (eliminaciones xs) es la lista de ternas (x,i,zs) tales que x es un elemento de xs, i es la posici\u00f3n de x en xs y zs es la lista de los restantes elementos de xs. Por ejemplo, \u03bb> eliminaciones [5,7,6,5] [(5,0,[7,6,5]),(7,1,[5,6,5]),(6,2,[5,7,5]),(5,3,[5,7,6])] Soluciones import Test.QuickCheck (quickCheck)&#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":[2,5],"tags":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/6110"}],"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=6110"}],"version-history":[{"count":2,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/6110\/revisions"}],"predecessor-version":[{"id":6160,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/6110\/revisions\/6160"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=6110"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=6110"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=6110"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}