failure 0.1.2 → 0.2.0.3

raw patch · 3 files changed

Files

• Control/Failure.hs +105/−95
• Setup.lhs +7/−7
• failure.cabal +25/−30

@@ -1,95 +1,105 @@-{-# LANGUAGE Rank2Types #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE UndecidableInstances #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE CPP #-}
--- | Type classes for returning failures.
-module Control.Failure
-    ( -- * Type class
-      Failure (..)
-      -- * Wrapping failures
-    , WrapFailure (..)
-      -- * Convenience 'String' failure
-    , StringException (..)
-    , failureString
-      -- * Convert 'Failure's into concrete types
-    , Try (..)
-    , NothingException (..)
-    , NullException (..)
-    ) where
-
-import Prelude hiding (catch)
-import Control.Exception (throw, catch, Exception, SomeException (..))
-import Data.Typeable (Typeable)
-#if !(MIN_VERSION_base(4,3,0))
-import Control.Monad.Trans.Error ()
-#else
-import Control.Monad.Instances ()
-#endif
-
-class Monad f => Failure e f where
-    failure :: e -> f v
-
-class Failure e f => WrapFailure e f where
-    -- | Wrap the failure value, if any, with the given function. This is
-    -- useful in particular when you want all the exceptions returned from a
-    -- certain library to be of a certain type, even if they were generated by
-    -- a different library.
-    wrapFailure :: (forall eIn. Exception eIn => eIn -> e) -> f a -> f a
-instance Exception e => WrapFailure e IO where
-    wrapFailure f m =
-        m `catch` \e@SomeException{} -> throw (f e)
-
-class Try f where
-  type Error f
-  -- Turn a concrete failure into an abstract failure
-  try :: Failure (Error f) f' => f a -> f' a
-
--- | Call 'failure' with a 'String'.
-failureString :: Failure StringException m => String -> m a
-failureString = failure . StringException
-
-newtype StringException = StringException String
-    deriving Typeable
-instance Show StringException where
-    show (StringException s) = "StringException: " ++ s
-instance Exception StringException
-
--- --------------
--- base instances
--- --------------
-
-instance Failure e Maybe where failure _ = Nothing
-instance Failure e []    where failure _ = []
-instance Failure e (Either e) where failure = Left
-
-instance Exception e => Failure e IO where
-  failure = Control.Exception.throw
-
--- not a monad or applicative instance Failure e (Either e) where failure = Left
-
-data NothingException = NothingException
-  deriving (Show, Typeable)
-instance Exception NothingException
-
-instance Try Maybe where
-  type Error Maybe = NothingException
-  try Nothing      = failure NothingException
-  try (Just x)     = return x
-
-instance Try (Either e) where
-  type Error (Either e) = e
-  try (Left  e)         = failure e
-  try (Right x)         = return x
-
-data NullException = NullException
-  deriving (Show, Typeable)
-instance Exception NullException
-
-instance Try [] where
-  type Error [] = NullException
-  try []        = failure NullException
-  try (x:_)     = return x
+{-# LANGUAGE MultiParamTypeClasses #-}+{-# LANGUAGE FlexibleInstances #-}+{-# LANGUAGE FlexibleContexts #-}+-- | Type classes for returning failures.+--+-- Note: This module used to contain a lot more functionality, but I believe it+-- was unused functionality. If you want any of it back, just email me.+module Control.Failure+    ( -- * Type class+      Failure (..)+      -- * General exceptions+    , exception+      {-+      -- * Wrapping failures+    , WrapFailure (..)+      -- * Convenience 'String' failure+    , StringException (..)+    , failureString+      -- * Convert 'Failure's into concrete types+    , Try (..)+    , NothingException (..)+    , NullException (..)+      -}+    ) where++import Control.Exception (throwIO, Exception (toException), SomeException (..))+import Control.Monad.Trans.Error ()+import Control.Monad.Trans.Class (MonadTrans (lift))++class Monad f => Failure e f where+    failure :: e -> f v++-- | Convert to a 'SomeException' via 'toException' before calling 'failure'.+exception :: (Exception e, Failure SomeException m) => e -> m a+exception = failure . toException++{-+class Failure e f => WrapFailure e f where+    -- | Wrap the failure value, if any, with the given function. This is+    -- useful in particular when you want all the exceptions returned from a+    -- certain library to be of a certain type, even if they were generated by+    -- a different library.+    wrapFailure :: (forall eIn. Exception eIn => eIn -> e) -> f a -> f a+instance Exception e => WrapFailure e IO where+    wrapFailure f m =+        m `catch` \e@SomeException{} -> throwIO (f e)++class Try f where+  type Error f+  -- Turn a concrete failure into an abstract failure+  try :: Failure (Error f) f' => f a -> f' a++-- | Call 'failure' with a 'String'.+failureString :: Failure StringException m => String -> m a+failureString = failure . StringException++newtype StringException = StringException String+    deriving Typeable+instance Show StringException where+    show (StringException s) = "StringException: " ++ s+instance Exception StringException+-}++-- --------------+-- base instances+-- --------------++instance Failure e Maybe where failure _ = Nothing+instance Failure e []    where failure _ = []+instance Failure e (Either e) where failure = Left++instance Exception e => Failure e IO where+  failure = throwIO++-- | Instance for all monad transformers, simply lift the @failure@ into the+-- base monad.+instance (MonadTrans t, Failure e m, Monad (t m)) => Failure e (t m) where+    failure = lift . failure++{-+-- not a monad or applicative instance Failure e (Either e) where failure = Left++data NothingException = NothingException+  deriving (Show, Typeable)+instance Exception NothingException++instance Try Maybe where+  type Error Maybe = NothingException+  try Nothing      = failure NothingException+  try (Just x)     = return x++instance Try (Either e) where+  type Error (Either e) = e+  try (Left  e)         = failure e+  try (Right x)         = return x++data NullException = NullException+  deriving (Show, Typeable)+instance Exception NullException++instance Try [] where+  type Error [] = NullException+  try []        = failure NullException+  try (x:_)     = return x+-}

@@ -1,7 +1,7 @@-#!/usr/bin/env runhaskell
-
-> module Main where
-> import Distribution.Simple
-
-> main :: IO ()
-> main = defaultMain
+#!/usr/bin/env runhaskell++> module Main where+> import Distribution.Simple++> main :: IO ()+> main = defaultMain

@@ -1,30 +1,25 @@-name: failure
-version: 0.1.2
-Cabal-Version:  >= 1.6
-build-type: Simple
-license: BSD3
-author: Pepe Iborra, Michael Snoyman, Nicolas Pouillard
-maintainer: pepeiborra@gmail.com
-homepage: http://www.haskell.org/haskellwiki/Failure
-description: A simple type class for success/failure computations.
-synopsis: A simple type class for success/failure computations.
-category: Control, Monads, Failure
-stability: stable
-
-flag base43
-
-Library
-  buildable: True
-  if flag(base43)
-    build-depends: base >= 4.3 && < 5
-  else
-    build-depends: base >= 4 && < 4.3
-                 , transformers >= 0.2 && < 0.3
-  ghc-options: -Wall
-
-  exposed-modules:
-     Control.Failure
-
-source-repository head
-  type:     git
-  location: git://github.com/snoyberg/failure.git
+name: failure+version: 0.2.0.3+Cabal-Version:  >= 1.6+build-type: Simple+license: BSD3+author: Pepe Iborra, Michael Snoyman, Nicolas Pouillard+maintainer: pepeiborra@gmail.com+homepage: http://www.haskell.org/haskellwiki/Failure+description: Please switch to the exceptions package+synopsis: A simple type class for success/failure computations. (deprecated)+category: Control, Monads, Failure+stability: stable++Library+  buildable: True+  build-depends: base         >= 4   && < 5+               , transformers >= 0.2+  ghc-options: -Wall++  exposed-modules:+     Control.Failure++source-repository head+  type:     git+  location: git://github.com/snoyberg/failure.git