{"id":7885,"date":"2023-02-09T06:00:57","date_gmt":"2023-02-09T04:00:57","guid":{"rendered":"http:\/\/www.glc.us.es\/~jalonso\/exercitium\/?p=7885"},"modified":"2023-01-24T11:10:41","modified_gmt":"2023-01-24T09:10:41","slug":"09-feb-23","status":"publish","type":"post","link":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/09-feb-23\/","title":{"rendered":"TAD de las colas: \u00daltimo elemento"},"content":{"rendered":"<p>Utilizando el <a href=\"https:\/\/bit.ly\/3QWTsRL\">tipo abstracto de datos de las colas<\/a>, definir la funci\u00f3n<\/p>\n<pre lang=\"text\">\n   ultimoCola :: Cola a -> a\n<\/pre>\n<p>tal que <code>ultimoCola c<\/code> es el \u00faltimo elemento de la cola <code>c<\/code>. Por ejemplo,<\/p>\n<pre lang=\"text\">\n   ultimoCola (inserta 3 (inserta 5 (inserta 2 vacia))) == 3\n   ultimoCola (inserta 2 vacia)                         == 2\n<\/pre>\n<p><b>Soluciones<\/b><\/p>\n<p>A continuaci\u00f3n se muestran las <a href=\"#haskell\">soluciones en Haskell<\/a> y las <a href=\"#python\">soluciones en Python<\/a>.<\/p>\n<p><a name=\"haskell\"><\/a><br \/>\n<b>Soluciones en Haskell<\/b><\/p>\n<pre lang=\"haskell\">\nimport TAD.Cola (Cola, vacia, inserta, primero, resto, esVacia)\nimport Transformaciones_colas_listas (colaAlista)\nimport Test.QuickCheck\n\n-- 1\u00aa soluci\u00f3n\n-- ===========\n\nultimoCola :: Cola a -> a\nultimoCola c\n  | esVacia c  = error \"cola vacia\"\n  | esVacia rc = pc\n  | otherwise  = ultimoCola rc\n  where pc = primero c\n        rc = resto c\n\n-- 2\u00aa soluci\u00f3n\n-- ===========\n\n-- Se usar\u00e1n la funci\u00f3n colaAlista del ejercicio\n-- \"Transformaciones entre colas y listas\" que se encuentra en\n-- https:\/\/bit.ly\/3Xv0oIt\n\nultimoCola2 :: Cola a -> a\nultimoCola2 c\n  | esVacia c  = error \"cola vacia\"\n  | otherwise  = last (colaAlista c)\n\n-- Comprobaci\u00f3n de equivalencia\n-- ============================\n\n-- La propiedad es\nprop_ultimoCola :: Cola Int -> Property\nprop_ultimoCola c =\n  not (esVacia c) ==> ultimoCola c == ultimoCola2 c\n\n-- La comprobaci\u00f3n es\n--    \u03bb> quickCheck prop_ultimoCola\n--    +++ OK, passed 100 tests; 16 discarded.\n<\/pre>\n<p><a name=\"python\"><\/a><br \/>\n<b>Soluciones en Python<\/b><\/p>\n<pre lang=\"python\">\nfrom copy import deepcopy\nfrom typing import TypeVar\n\nfrom hypothesis import assume, given\n\nfrom src.TAD.cola import (Cola, colaAleatoria, esVacia, inserta, primero,\n                          resto, vacia)\nfrom src.transformaciones_colas_listas import colaAlista\n\nA = TypeVar('A')\n\n# 1\u00aa soluci\u00f3n\n# ===========\n\ndef ultimoCola(c: Cola[A]) -> A:\n    if esVacia(c):\n        raise ValueError(\"cola vacia\")\n    pc = primero(c)\n    rc = resto(c)\n    if esVacia(rc):\n        return pc\n    return ultimoCola(rc)\n\n# 2\u00aa soluci\u00f3n\n# ===========\n\ndef ultimoCola2Aux(c: Cola[A]) -> A:\n    if c.esVacia():\n        raise ValueError(\"cola vacia\")\n    pc = primero(c)\n    c.resto()\n    if c.esVacia():\n        return pc\n    return ultimoCola2(c)\n\ndef ultimoCola2(c: Cola[A]) -> A:\n    _c = deepcopy(c)\n    return ultimoCola2Aux(_c)\n\n# 3\u00aa soluci\u00f3n\n# ===========\n\ndef ultimoCola3(c: Cola[A]) -> A:\n    if esVacia(c):\n        raise ValueError(\"cola vacia\")\n    while not esVacia(resto(c)):\n        c = resto(c)\n    return primero(c)\n\n# 4\u00aa soluci\u00f3n\n# ===========\n\ndef ultimoCola4Aux(c: Cola[A]) -> A:\n    if c.esVacia():\n        raise ValueError(\"cola vacia\")\n    r = primero(c)\n    while not c.esVacia():\n        c.resto()\n        if not c.esVacia():\n            r = primero(c)\n    return r\n\ndef ultimoCola4(c: Cola[A]) -> A:\n    _c = deepcopy(c)\n    return ultimoCola4Aux(_c)\n\n# 5\u00aa soluci\u00f3n\n# ===========\n\n# Se usar\u00e1n la funci\u00f3n colaAlista del ejercicio\n# \"Transformaciones entre colas y listas\" que se encuentra en\n# https:\/\/bit.ly\/3Xv0oIt\n\ndef ultimoCola5(c: Cola[A]) -> A:\n    if esVacia(c):\n        raise ValueError(\"cola vacia\")\n    return colaAlista(c)[-1]\n\n# Comprobaci\u00f3n de equivalencia\n# ============================\n\n# La propiedad es\n@given(c=colaAleatoria())\ndef test_ultimoCola(c: Cola[int]) -> None:\n    assume(not esVacia(c))\n    r = ultimoCola(c)\n    assert ultimoCola2(c) == r\n    assert ultimoCola3(c) == r\n    assert ultimoCola4(c) == r\n    assert ultimoCola5(c) == r\n\n# La comprobaci\u00f3n es\n#      src> poetry run pytest -q ultimoCola.py\n#      1 passed in 0.25s\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Utilizando el tipo abstracto de datos de las colas, definir la funci\u00f3n ultimoCola :: Cola a -> a tal que ultimoCola c es el \u00faltimo elemento de la cola c. Por ejemplo, ultimoCola (inserta 3 (inserta 5 (inserta 2 vacia))) == 3 ultimoCola (inserta 2 vacia) == 2 Soluciones A continuaci\u00f3n se muestran las soluciones&#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":[581],"tags":[515,585],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7885"}],"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=7885"}],"version-history":[{"count":2,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7885\/revisions"}],"predecessor-version":[{"id":7890,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/posts\/7885\/revisions\/7890"}],"wp:attachment":[{"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/media?parent=7885"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/categories?post=7885"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.glc.us.es\/~jalonso\/exercitium\/wp-json\/wp\/v2\/tags?post=7885"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}