khibino/haskell-relational-record
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Switch to use wrapped either.

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This commit is contained in:
Kei Hibino 2015-11-05 20:03:10 +09:00
parent 17ba0e0ef5
commit 11614993db
1 changed files with 6 additions and 9 deletions
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15
postgresql-text/src/Text/Parser/List.hs
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@ -11,27 +11,24 @@ import Control.Monad.Trans.State.Strict (StateT (..), evalStateT, get, put)
import Data.Monoid (Last (..))
import Data.Maybe (fromMaybe)
import Control.Monad.Either.Instances ()
import Control.Monad.Either.Plus (EitherP (..), emap, leftP)
emap :: (e0 -> e1) -> Either e0 a -> Either e1 a
emap f = either (Left . f) Right
type Error = Last String
unError :: String -> Error -> String
unError s = fromMaybe s . getLast
type Parser t = StateT [t] (Either Error)
type Parser t = StateT [t] (EitherP Error)
runParser :: Parser t a -> [t] -> Either String (a, [t])
runParser p = emap (unError "runParser: parse error.") . runStateT p
runParser p = unEitherP . emap (unError "runParser: parse error.") . runStateT p
evalParser :: Parser t a -> [t] -> Either String a
evalParser p = emap (unError "evalParser: parse error.") . evalStateT p
evalParser p = unEitherP . emap (unError "evalParser: parse error.") . evalStateT p
errorE :: String -> Either Error a
errorE = Left . Last . Just
errorE :: String -> EitherP Error a
errorE = leftP . Last . Just
errorP :: String -> Parser t a
errorP = StateT . const . errorE