untested: inform clients about remote presences

1 files changed, 6 insertions, 0 deletions

diff --git a/TraversableT.hs b/TraversableT.hs
index cd04731c..98a97bf6 100644
--- a/TraversableT.hs
+++ b/TraversableT.hs
@@ -5,6 +5,7 @@ import Control.Monad (join,MonadPlus(..))
 import Control.Monad.Trans.Class
 import Control.Applicative
 import Data.Foldable (Foldable(foldMap))
+import Data.Maybe (maybeToList)
 
 -- | 
 --
@@ -75,4 +76,9 @@ liftCatch :: (m (t a) -> (e -> m (t a)) -> m (t a)) ->
 liftCatch catchError m h = TraversableT $ runTraversableT m
     `catchError` \e -> runTraversableT (h e)
 
+liftMaybe :: Monad m => Maybe a -> TraversableT [] m a
+liftMaybe = liftT . maybeToList
+
+liftIOMaybe :: IO (Maybe a) -> TraversableT [] IO a
+liftIOMaybe = liftMT . fmap maybeToList