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module Pattern where
import Data.Char
import Data.Text.Lazy (Text)
import qualified Data.Text.Lazy as T
data Pattern = Pattern Text [Origin]
deriving (Show)
data Origin = OCopy
| ONew Text
deriving (Show)
parsePattern :: String -> Either String Pattern
parsePattern str = do
(constr, args) <- case words str of
[] -> Left "Empty match pattern"
constr : args -> return (constr, args)
args' <- traverse parseArg args
return (Pattern (T.pack constr) args')
where
parseArg :: String -> Either String Origin
parseArg ('*':name) | isValid name = Right (ONew (T.pack name))
| otherwise = Left ("Invalid type param name '" ++ name ++ "'")
parseArg name | isValid name = Right OCopy
| otherwise = Left ("Invalid type param name '" ++ name ++ "'")
isValid :: String -> Bool
isValid "" = False
isValid (hd:cs) = isLower hd && all (\c -> isAlpha c || c `elem` "'_") cs
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