Add MonadPlus

Author: garyb

docs/Module.md

@@ -31,6 +31,8 @@
 
     instance monadParserT :: (Monad m) => Monad (ParserT s m)
 
+    instance monadPlusParserT :: (Monad m) => MonadPlus (ParserT s m)
+
     instance monadStateParserT :: (Monad m) => MonadState s (ParserT s m)
 
     instance monadTransParserT :: MonadTrans (ParserT s)

src/Text/Parsing/Parser.purs

@@ -16,6 +16,7 @@ import Control.Monad.State.Trans
 import Control.Monad.Error
 import Control.Monad.Error.Class
 import Control.Monad.Error.Trans
+import Control.MonadPlus
 
 data ParseError = ParseError
   { message :: String
@@ -72,6 +73,8 @@ instance bindParserT :: (Monad m) => Bind (ParserT s m) where
 
 instance monadParserT :: (Monad m) => Monad (ParserT s m)
 
+instance monadPlusParserT :: (Monad m) => MonadPlus (ParserT s m)
+
 instance monadTransParserT :: MonadTrans (ParserT s) where
   lift m = ParserT $ \s -> (\a -> { input: s, consumed: false, result: Right a }) <$> m