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Monthly Downloads: 6
Programming language: Haskell
License: BSD 3-clause "New" or "Revised" License
Tags: Data     Regex    
Latest version: v0.1.0.0
Add another 'regex' Package

README

Experimental

This library allows you to create types that are guaranteed to contain a string that matches a given regular expression which is expressed at the type level.

newtype User = User (Matched String "^[a-zA-Z0-9]{4,15}$")

parseUser :: String -> Either (RegexError String) User
parseUser = fmap User . parseMatchedEither

prettyUser :: User -> String
prettyUser (User m) = asString m

main :: IO ()
main = do
    l <- getLine
    case parseUser l of
        Right user -> putStrLn $ "Hello, " ++ prettyUser user ++ "!"
        Left error -> putStrLn $ "Could not parse username: " ++ prettyRegexError  error
./prog
bad
Could not parse username: The input "bad" did not match the pattern ^[a-zA-Z0-9]{4,15}$
./prog
good
Hello, good!