{"id":547,"date":"2014-11-05T07:00:42","date_gmt":"2014-11-05T05:00:42","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=547"},"modified":"2014-12-27T21:38:19","modified_gmt":"2014-12-27T19:38:19","slug":"suma-de-todos-los-anteriores","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/suma-de-todos-los-anteriores\/","title":{"rendered":"Suma de todos los anteriores."},"content":{"rendered":"<h4>Enunciado<\/h4>\n<pre lang=\"text\">\n-- Definir la funci\u00f3n\n--    sumaAnteriores :: [Integer] -> Bool\n-- tal que (sumaAnteriores xs) se verifica si cada elemento de la lista\n-- xs (excepto el primero) es la suma de sus anteriores elementos en la\n-- lista. Por ejemplo,  \n--    sumaAnteriores [3,3,6,12]  ==  True\n--    sumaAnteriores [3,3,7,10]  ==  False\n--    sumaAnteriores [3]         ==  True\n--    sumaAnteriores []          ==  True\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Test.QuickCheck\n\n-- 1\u00aa definici\u00f3n (por recursi\u00f3n):\nsumaAnteriores :: [Integer] -> Bool\nsumaAnteriores xs = aux (reverse xs)\n    where aux []     = True\n          aux [_]    = True\n          aux (x:xs) = x == sum xs && aux xs\n\n-- 2\u00aa definici\u00f3n (por comprensi\u00f3n):\nsumaAnteriores2 :: [Integer] -> Bool\nsumaAnteriores2 (x:y:zs) = \n    x == y && and [b == 2*a | (a,b) <- adyacentes (y:zs)]\n    where adyacentes xs = zip xs (tail xs)\nsumaAnteriores2 _ = True\n\n-- La propiedad de equivalencia es\nprop_equiv_sumaAnteriores :: [Integer] -> Bool\nprop_equiv_sumaAnteriores xs = \n    sumaAnteriores xs == sumaAnteriores2 xs\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Enunciado &#8212; Definir la funci\u00f3n &#8212; sumaAnteriores :: [Integer] -> Bool &#8212; tal que (sumaAnteriores xs) se verifica si cada elemento de la lista &#8212; xs (excepto el primero) es la suma de sus anteriores elementos en la &#8212; lista. Por ejemplo, &#8212; sumaAnteriores [3,3,6,12] == True &#8212; sumaAnteriores [3,3,7,10] == False &#8212; sumaAnteriores [3]&#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":[100,8,6,32,40,45,9],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/547"}],"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=547"}],"version-history":[{"count":6,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/547\/revisions"}],"predecessor-version":[{"id":746,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/547\/revisions\/746"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=547"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=547"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=547"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}