phoneBook.hs

import Data.Char
import qualified Data.Map as Map

phoneBook :: Map.Map String String
phoneBook = Map.fromList $
            [("betty", "555-2938")
            ,("bonnie", "452-2928")
            ,("patsy", "493-2928")
            ,("lucille", "205-2928")
            ,("wendy", "939-8282")
            ,("penny", "853-2492")
            ]

string2digits :: String -> [Int]
string2digits = map digitToInt . filter isDigit

main = do
    print $ Map.lookup "grace" phoneBook -- 該当しない場合はNothing
    let newBook = Map.insert "grace" "341-9021" phoneBook
    print $ Map.lookup "grace" newBook
    print $ Map.size phoneBook
    print $ Map.size newBook
    print $ string2digits "948-9282"
    let intBook = Map.map string2digits phoneBook
    print $ Map.lookup "betty" intBook