maybe_email.hs

-- just giving functors and the applicative operators a test drive

import Control.Applicative
import Data.Char

emails :: [String]
emails = ["Kenny@northpole.sg", "Wutever@Evalution.com", "somethingthatsmellslikeSPAM", "h@iamvalidemail.org", "NOTSPAM@SPAM.NET"]

hasAt :: [Char] -> Bool

hasAt [] = False
hasAt (x:xs) | x == '@' = True
             | otherwise = hasAt xs

main = print $ (++) <$> ["Maybe valid: "] <*> (filter hasAt $ [(map toLower) email | email <- emails])