Merge branch 'master' into topic/rwst-monad-rec

Author: ethul

docs/Control/Monad/RWS/Trans.md

@@ -37,6 +37,7 @@ instance monadReaderRWST :: (Monad m, Monoid w) => MonadReader r (RWST r w s m)
 instance monadStateRWST :: (Monad m, Monoid w) => MonadState s (RWST r w s m)
 instance monadWriterRWST :: (Monad m, Monoid w) => MonadWriter w (RWST r w s m)
 instance monadRWSRWST :: (Monad m, Monoid w) => MonadRWS r w s (RWST r w s m)
+instance monadErrorRWST :: (MonadError e m, Monoid w) => MonadError e (RWST r w s m)
 instance monadRecRWST :: (Monoid w, MonadRec m) => MonadRec (RWST r w s m)
 ```
 

docs/Control/Monad/Reader/Trans.md

@@ -35,6 +35,7 @@ instance monadReaderReaderT :: (Monad m) => MonadReader r (ReaderT r m)
 instance monadStateReaderT :: (MonadState s m) => MonadState s (ReaderT r m)
 instance monadWriterReaderT :: (Monad m, MonadWriter w m) => MonadWriter w (ReaderT r m)
 instance distributiveReaderT :: (Distributive g) => Distributive (ReaderT e g)
+instance monadRecReaderT :: (MonadRec m) => MonadRec (ReaderT r m)
 ```
 
 #### `runReaderT`

src/Control/Monad/RWS/Trans.purs

@@ -1,6 +1,6 @@
 -- | This module defines the reader-writer-state monad transformer, `RWST`.
 
-module Control.Monad.RWS.Trans 
+module Control.Monad.RWS.Trans
   ( See(), mkSee
   , RWST(..), runRWST, evalRWST, execRWST, mapRWST, withRWST
   , module Control.Monad.Trans
@@ -13,13 +13,14 @@ import Data.Either
 import Data.Monoid
 import Data.Tuple
 
-import Control.Monad.Trans
 import Control.Monad.Eff.Class
+import Control.Monad.Error.Class
+import Control.Monad.RWS.Class
 import Control.Monad.Rec.Class
 import Control.Monad.Reader.Class
-import Control.Monad.Writer.Class
 import Control.Monad.State.Class
-import Control.Monad.RWS.Class
+import Control.Monad.Trans
+import Control.Monad.Writer.Class
 
 type See s a w =
   { state  :: s
@@ -94,6 +95,10 @@ instance monadWriterRWST :: (Monad m, Monoid w) => MonadWriter w (RWST r w s m)
 
 instance monadRWSRWST :: (Monad m, Monoid w) => MonadRWS r w s (RWST r w s m)
 
+instance monadErrorRWST :: (MonadError e m, Monoid w) => MonadError e (RWST r w s m) where
+  throwError e = lift (throwError e)
+  catchError m h = RWST $ \r s -> catchError (runRWST m r s) (\e -> runRWST (h e) r s)
+
 instance monadRecRWST :: (Monoid w, MonadRec m) => MonadRec (RWST r w s m) where
   tailRecM k a = RWST \r s -> tailRecM (k' r) { writer: mempty, state: s, result: a }
     where

src/Control/Monad/Reader/Trans.purs

@@ -16,12 +16,15 @@ import Control.Monad.Eff.Class
 import Control.Monad.Cont.Class
 import Control.Monad.Error.Class
 import Control.Monad.Reader.Class
+import Control.Monad.Rec.Class
 import Control.Monad.State.Class
 import Control.Monad.Writer.Class
 import Control.Monad.Trans
 import Control.MonadPlus
 import Control.Plus
 
+import Data.Either
+
 -- | The reader monad transformer.
 -- |
 -- | This monad transformer extends the base monad transformer with a _global context_ of
@@ -96,3 +99,10 @@ instance monadWriterReaderT :: (Monad m, MonadWriter w m) => MonadWriter w (Read
 instance distributiveReaderT :: (Distributive g) => Distributive (ReaderT e g) where
   distribute a = ReaderT \e -> collect (flip runReaderT e) a
   collect f = distribute <<< map f
+
+instance monadRecReaderT :: (MonadRec m) => MonadRec (ReaderT r m) where
+  tailRecM k a = ReaderT \r -> tailRecM (k' r) a
+    where
+    k' r a = do
+      result <- runReaderT (k a) r
+      return $ either Left Right result