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Diffstat (limited to 'src/Language/GraphQL/Trans.hs')
| -rw-r--r-- | src/Language/GraphQL/Trans.hs | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/src/Language/GraphQL/Trans.hs b/src/Language/GraphQL/Trans.hs new file mode 100644 index 0000000..f0fcefb --- /dev/null +++ b/src/Language/GraphQL/Trans.hs @@ -0,0 +1,35 @@ +module Language.GraphQL.Trans where + +import Control.Applicative (Alternative(..)) +import Control.Monad (MonadPlus(..)) +import Control.Monad.IO.Class (MonadIO(..)) +import Control.Monad.Trans.Class (MonadTrans(..)) +import Control.Monad.Trans.Except (ExceptT) +import Data.Text (Text) + +newtype ActionT m a = ActionT { runActionT :: ExceptT Text m a } + +instance Functor m => Functor (ActionT m) where + fmap f = ActionT . fmap f . runActionT + +instance Monad m => Applicative (ActionT m) where + pure = ActionT . pure + (ActionT f) <*> (ActionT x) = ActionT $ f <*> x + +instance Monad m => Monad (ActionT m) where + return = pure + (ActionT action) >>= f = ActionT $ action >>= runActionT . f + +instance MonadTrans ActionT where + lift = ActionT . lift + +instance MonadIO m => MonadIO (ActionT m) where + liftIO = lift . liftIO + +instance Monad m => Alternative (ActionT m) where + empty = ActionT empty + (ActionT x) <|> (ActionT y) = ActionT $ x <|> y + +instance Monad m => MonadPlus (ActionT m) where + mzero = empty + mplus = (<|>) |
