Sustitución de listas

José A. Alonso

22-01-2015

Definir la función

sustituye :: Eq a => [a] -> [a] -> [a] -> [a]

tal que (sustituye xs ys zs) es la lista obtenida sustituyendo las ocurrencias de xs en zs por ys. Por ejemplo,

sustituye "as" "_" "las casaderas"   ==  "l_ c_ader_"
sustituye "as" "es" "las casaderas"  ==  "les cesaderes"
sustituye "asa" "a" "las casaderas"  ==  "las caderas"
sustituye "asd" "a" "las casaderas"  ==  "las casaderas"

Soluciones

import Data.List (isPrefixOf)

sustituye :: Eq a => [a] -> [a] -> [a] -> [a]
sustituye xs ys [] = []
sustituye xs ys (z:zs)
    | isPrefixOf xs (z:zs) = ys ++ sustituye xs ys (drop n zs)
    | otherwise            = z : sustituye xs ys zs
    where n = length xs - 1