FailureT (empty) → 15321.1

raw patch · 6 files changed

+247/−0 lines, 6 filesdep +basedep +mmtlsetup-changed

Dependencies added: base, mmtl

Files

• Control/Monad/Failure.hs +44/−0
• Control/Monad/Failure/Class.hs +9/−0
• Control/Monad/Failure/Instances.hs +10/−0
• FailureT.cabal +17/−0
• Setup.hs +2/−0
• license.txt +165/−0

@@ -0,0 +1,44 @@+module Control.Monad.Failure (module Control.Monad.Failure.Class, FailureT (..)) where++import Prelude hiding (fail);++import Control.Monad hiding (fail);+import Control.Monad.Fix;+import Control.Monad.Trans;+import Control.Monad.Failure.Class;+import Data.Traversable;++newtype FailureT f m a = FailureT { runFailureT :: m (Either f a) };++mapFailureT :: (m (Either f a) -> n (Either f b)) -> FailureT f m a -> FailureT f n b;+mapFailureT f = FailureT . f . runFailureT;++instance MonadTrans (FailureT f) where {+  lift = FailureT . liftM Right;+  tmap f _ = mapFailureT f;+};++instance Functor m => Functor (FailureT f m) where {+  fmap = mapFailureT . fmap . fmap;+};++instance Monad m => Monad (FailureT f m) where {+  return = lift . return;+  FailureT x >>= f = FailureT $ x >>= liftM join . either (liftM Left . return) (liftM Right . runFailureT . f);+};++instance MonadFix m => MonadFix (FailureT f m) where {+  mfix f = FailureT $ mfix (either (return . Left) (runFailureT . f));+};++instance (Monad m, MonadTrans xT, Monad (xT (FailureT f m))) => MonadFailure f (xT (FailureT f m)) where {+  fail = lift . fail;+};++instance Monad m => MonadFailure f (FailureT f m) where {+  fail = FailureT . return . Left;+};++instance Monad m => MonadSalvage f (FailureT f m) where {+  save f = mapFailureT (>>= runFailureT . either f return);+};

@@ -0,0 +1,9 @@+module Control.Monad.Failure.Class where++class Monad m => MonadFailure f m where {+  fail :: f -> m a;+};++class MonadFailure f m => MonadSalvage f m where {+  save :: (f -> m a) -> m a -> m a;+};

@@ -0,0 +1,10 @@+module Control.Monad.Failure.Instances where++import Control.Exception;+import Control.Monad.Failure.Class;++instance (Exception e) => MonadFailure e IO where fail = throwIO;++instance (Exception e) => MonadSalvage e IO where save = handle;++instance MonadFailure f Maybe where fail = const Nothing;

@@ -0,0 +1,17 @@+Name:FailureT+Version:15321.1+Description:Failure Monad Transformer+License:LGPL+License-File:license.txt+Author:Matthew Farkas-Dyck+Maintainer:strake888@gmail.com+Category:Control, Failure+Synopsis:Failure Monad Transformer+Build-Type:Simple+Cabal-Version: >= 1.2++Library {+  Build-Depends: base >= 4 && < 5, mmtl+  Extensions: MultiParamTypeClasses, FlexibleContexts, FlexibleInstances+  Exposed-Modules: Control.Monad.Failure, Control.Monad.Failure.Class, Control.Monad.Failure.Instances+}

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

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