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module Main where | |
import Control.Monad | |
import Data.Char | |
import Data.Either | |
import Data.List.Split | |
type PhonebookError = String | |
data PhonebookEntry = PhonebookEntry | |
{ pe_name :: String | |
, pe_numbers :: [Int] | |
} deriving Show | |
parseName :: String -> Either PhonebookError String | |
parseName = | |
foldr | |
(\c result -> | |
result >>= \name -> | |
if (c < 'a' || c > 'z') && (c < 'A' || c > 'Z') && c /= ' ' then | |
Left $ "Invalid character " ++ [c] ++ "!" | |
else | |
Right $ c : name | |
) | |
(Right "") | |
parsePhoneNumber :: String -> Either PhonebookError Int | |
parsePhoneNumber ('0' : _) = Left "Phone number cannot begin with zero!" | |
parsePhoneNumber phoneNumber = | |
foldl | |
(\result c -> | |
let n = ord c - ord '0' | |
in result >>= \number -> | |
if n < 0 || n > 9 then | |
Left $ "Invalid Character " ++ [c] ++ "!" | |
else | |
Right $ 10 * number + n | |
) | |
(Right 0) | |
phoneNumber | |
parsePhoneNumbers :: String -> Either PhonebookError [Int] | |
parsePhoneNumbers = | |
mapM parsePhoneNumber . words | |
parseArguments :: [String] -> Either PhonebookError PhonebookEntry | |
parseArguments [name, phoneNumbers] = | |
liftM2 PhonebookEntry (parseName name) (parsePhoneNumbers phoneNumbers) | |
parseArguments xs = Left $ "Expected 2 arguments, got " ++ (show $ length xs) ++ "!" | |
parseLine :: String -> Either PhonebookError PhonebookEntry | |
parseLine = parseArguments . splitOn ": " | |
main :: IO () | |
main = do | |
let goodPhonebook = "John Doe: 1337 69 420" | |
malformedPhonebook = "This is a malformed phone book!" | |
mapM_ | |
(print . fromRight "Uh-oh, that doesn't work this way!" . (show <$>) . parseLine) | |
[goodPhonebook, malformedPhonebook] | |
pure () |
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