{"id":7515,"date":"2022-11-15T06:00:59","date_gmt":"2022-11-15T04:00:59","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=7515"},"modified":"2022-12-14T11:43:27","modified_gmt":"2022-12-14T09:43:27","slug":"15-nov-22","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/15-nov-22\/","title":{"rendered":"Segmentos cuyos elementos cumplen una propiedad"},"content":{"rendered":"

Definir la funci\u00f3n<\/p>\n

\n   segmentos :: (a -> Bool) -> [a] -> [[a]]\n<\/pre>\n
tal que segmentos p xs<\/code> es la lista de los segmentos de xs<\/code> cuyos elementos verifican la propiedad p<\/code>. Por ejemplo,<\/p>\n
\n   segmentos even [1,2,0,4,9,6,4,5,7,2]  ==  [[2,0,4],[6,4],[2]]\n   segmentos odd  [1,2,0,4,9,6,4,5,7,2]  ==  [[1],[9],[5,7]]\n<\/pre>\n
Soluciones<\/b><\/p>\n
A continuaci\u00f3n se muestran las soluciones en Haskell<\/a> y las soluciones en Python<\/a>.<\/p>\n
<\/a>
\nSoluciones en Haskell<\/b><\/p>\n
\nimport Data.List.Split (splitWhen)\nimport Test.QuickCheck.HigherOrder (quickCheck')\n\n-- 1\u00aa soluci\u00f3n\n-- ===========\n\nsegmentos1 :: (a -> Bool) -> [a] -> [[a]]\nsegmentos1 _ [] = []\nsegmentos1 p (x:xs)\n  | p x       = takeWhile p (x:xs) : segmentos1 p (dropWhile p xs)\n  | otherwise = segmentos1 p xs\n\n-- 2\u00aa soluci\u00f3n\n-- ===========\n\nsegmentos2 :: (a -> Bool) -> [a] -> [[a]]\nsegmentos2 p xs = filter (not .null) (splitWhen (not . p) xs)\n\n-- 3\u00aa soluci\u00f3n\n-- ===========\n\nsegmentos3 :: (a -> Bool) -> [a] -> [[a]]\nsegmentos3 = (filter (not . null) .) . splitWhen . (not .)\n\n-- Comprobaci\u00f3n de equivalencia\n-- ============================\n\n-- La propiedad es\nprop_segmentos :: (Int -> Bool) -> [Int] -> Bool\nprop_segmentos p xs =\n  all (== segmentos1 p xs)\n      [segmentos2 p xs,\n       segmentos3 p xs]\n\n-- La comprobaci\u00f3n es\n--    \u03bb> quickCheck' prop_segmentos\n--    +++ OK, passed 100 tests.\n\n-- Comparaci\u00f3n de eficiencia\n-- =========================\n\n-- La comparaci\u00f3n es\n--    \u03bb> length (segmentos1 even [1..5*10^6])\n--    2500000\n--    (2.52 secs, 2,080,591,088 bytes)\n--    \u03bb> length (segmentos2 even [1..5*10^6])\n--    2500000\n--    (0.78 secs, 2,860,591,688 bytes)\n--    \u03bb> length (segmentos3 even [1..5*10^6])\n--    2500000\n--    (0.82 secs, 2,860,592,000 bytes)\n<\/pre>\n
<\/a>
\nSoluciones en Python<\/b><\/p>\n
\nfrom itertools import dropwhile, takewhile\nfrom sys import setrecursionlimit\nfrom timeit import Timer, default_timer\nfrom typing import Callable, TypeVar\n\nfrom more_itertools import split_at\n\nsetrecursionlimit(10**6)\n\nA = TypeVar('A')\n\n# 1\u00aa soluci\u00f3n\n# ===========\n\ndef segmentos1(p: Callable[[A], bool], xs: list[A]) -> list[list[A]]:\n    if not xs:\n        return []\n    if p(xs[0]):\n        return [list(takewhile(p, xs))] + \\\n            segmentos1(p, list(dropwhile(p, xs[1:])))\n    return segmentos1(p, xs[1:])\n\n# 2\u00aa soluci\u00f3n\n# ===========\n\ndef segmentos2(p: Callable[[A], bool], xs: list[A]) -> list[list[A]]:\n    return list(filter((lambda x: x), split_at(xs, lambda x: not p(x))))\n\n# Comparaci\u00f3n de eficiencia\n# =========================\n\ndef tiempo(e: str) -> None:\n    \"\"\"Tiempo (en segundos) de evaluar la expresi\u00f3n e.\"\"\"\n    t = Timer(e, \"\", default_timer, globals()).timeit(1)\n    print(f\"{t:0.2f} segundos\")\n\n# La comparaci\u00f3n es\n#    >>> tiempo('segmentos1(lambda x: x % 2 == 0, range(10**4))')\n#    0.55 segundos\n#    >>> tiempo('segmentos2(lambda x: x % 2 == 0, range(10**4))')\n#    0.00 segundos\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
Definir la funci\u00f3n segmentos :: (a -> Bool) -> [a] -> [[a]] tal que segmentos p xs es la lista de los segmentos de xs cuyos elementos verifican la propiedad p. Por ejemplo, segmentos even [1,2,0,4,9,6,4,5,7,2] == [[2,0,4],[6,4],[2]] segmentos odd [1,2,0,4,9,6,4,5,7,2] == [[1],[9],[5,7]] Soluciones A continuaci\u00f3n se muestran las soluciones en Haskell y las soluciones…<\/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":[581],"tags":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7515"}],"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=7515"}],"version-history":[{"count":2,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7515\/revisions"}],"predecessor-version":[{"id":7648,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7515\/revisions\/7648"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=7515"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=7515"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=7515"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}