{"id":979,"date":"2015-01-19T06:00:33","date_gmt":"2015-01-19T04:00:33","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=979"},"modified":"2015-11-30T19:28:35","modified_gmt":"2015-11-30T17:28:35","slug":"suma-de-una-lista-de-vectores","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/suma-de-una-lista-de-vectores\/","title":{"rendered":"Suma de una lista de vectores"},"content":{"rendered":"<p>Definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   sumaVec :: Num a => [[a]] -> [a]\n<\/pre>\n<p>tal que (sumaVec xss) es la suma de los vectores de xss. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   sumaVec [[4,7,3],[3,1,4],[2,2,5]]  ==  [9,10,12]\n   sumaVec [[4,7],[3,3],[1,4],[2,5]]  ==  [10,19]\n<\/pre>\n<h4>Soluciones<\/h4>\n<pre lang=\"haskell\">\nimport Data.List (transpose)\nimport Data.Array (listArray,(!))\n\n-- 1\u00aa definici\u00f3n (por recursi\u00f3n):\nsumaVec1 :: Num a => [[a]] -> [a]\nsumaVec1 []          = []\nsumaVec1 [xs]        = xs\nsumaVec1 (xs:ys:zss) = suma xs (sumaVec1 (ys:zss))\n\n-- (suma xs ys) es la suma de los vectores xs e ys. Por ejemplo,\n--    suma [4,7,3] [1,2,5]  == [5,9,8]\nsuma :: Num a => [a] -> [a] -> [a]\nsuma [] []         = []\nsuma (x:xs) (y:ys) = x+y : suma xs ys\n\n-- 2\u00aa definici\u00f3n (por recursi\u00f3n con zipWith): \nsumaVec2 :: Num a => [[a]] -> [a]\nsumaVec2 []       = []\nsumaVec2 [xs]     = xs\nsumaVec2 (xs:xss) = zipWith (+) xs (sumaVec2 xss)\n\n-- 3\u00aa definici\u00f3n (por plegado)\nsumaVec3 :: Num a => [[a]] -> [a]\nsumaVec3 = foldr1 (zipWith (+))\n\n-- 4\u00aa definici\u00f3n (con map y transpose):\nsumaVec4 :: Num a => [[a]] -> [a]\nsumaVec4 = map sum . transpose \n\n-- 5\u00aa definici\u00f3n (con array)\n-- =========================\n\nsumaVec5 :: Num a => [[a]] -> [a]\nsumaVec5 xss = [sum [p!(i,j) | i <- [1..m]] | j <- [1..n]] \n    where m = length xss\n          n = length (head xss)\n          p = listArray ((1,1),(m,n)) (concat xss) \n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Definir la funci\u00f3n sumaVec :: Num a => [[a]] -> [a] tal que (sumaVec xss) es la suma de los vectores de xss. Por ejemplo, sumaVec [[4,7,3],[3,1,4],[2,2,5]] == [9,10,12] sumaVec [[4,7],[3,3],[1,4],[2,5]] == [10,19] Soluciones import Data.List (transpose) import Data.Array (listArray,(!)) &#8212; 1\u00aa definici\u00f3n (por recursi\u00f3n): sumaVec1 :: Num a => [[a]] -> [a] sumaVec1 []&#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":[12,243,71,28,72,10,42,11,90,6,40,68,76],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/979"}],"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=979"}],"version-history":[{"count":4,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/979\/revisions"}],"predecessor-version":[{"id":1802,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/979\/revisions\/1802"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=979"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=979"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=979"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}