module System.Console.GetOpt.Generics.Result where
import Control.Applicative
data Result a
= Success a
| Errors [String]
| OutputAndExit String
deriving (Show, Eq, Ord, Functor)
instance Applicative Result where
pure = Success
OutputAndExit message <*> _ = OutputAndExit message
_ <*> OutputAndExit message = OutputAndExit message
Success f <*> Success x = Success (f x)
Errors a <*> Errors b = Errors (a ++ b)
Errors errs <*> Success _ = Errors errs
Success _ <*> Errors errs = Errors errs
instance Monad Result where
return = pure
Success a >>= b = b a
Errors errs >>= _ = Errors errs
OutputAndExit message >>= _ = OutputAndExit message
(>>) = (*>)