Added default functions, isEmpty does not typecheck...

[cc1516.git] / RWST.dcl

diff --git a/RWST.dcl b/RWST.dcl
index 70a07e1..582bb0d 100644 (file)
--- a/RWST.dcl
+++ b/RWST.dcl
@@ -2,6 +2,7 @@ definition module RWST
 
 from Control.Applicative import class Applicative
 from Control.Monad import class Monad
+from Control.Monad.Trans import class MonadTrans
 from Data.Functor import class Functor
 from Data.Functor.Identity import :: Identity
 from Data.Monoid import class Monoid, class Semigroup
@@ -22,6 +23,7 @@ withRWS :: (r` s -> (r, s)) (RWS r w s a) -> RWS r` w s a
 instance Functor (RWST r w s m) | Monad m & Monoid w
 instance Applicative (RWST r w s m) | Monad m & Monoid w
 instance Monad (RWST r w s m) | Monad m & Monoid w
+instance MonadTrans (RWST r w s) | Monoid w
 
 runRWST :: (RWST r w s m a) r s -> m (a, s, w)
 evalRWST :: (RWST r w s m a) r s -> m (a, w) | Monad m