Unverified Commit 1a7d01fb authored by Fumiaki Kinoshita's avatar Fumiaki Kinoshita 💬 Committed by GitHub

Remove ListT/ErrorT-related stuff (#76)

* Remove ListT/ErrorT-related stuff
parent a9023c76
......@@ -4,6 +4,8 @@ Unreleased
* `Control.Monad.Cont` now re-exports `evalCont` and `evalContT`
* Add `tryError`, `withError`, `handleError`, and `mapError` to
`Control.Monad.Error.Class`, and re-export from `Control.Monad.Except`.
* Remove `Control.Monad.List` and `Control.Monad.Error`
* Remove instances of deprecated `ListT` and `ErrorT`
2.2.2
-----
......
......@@ -55,10 +55,8 @@ module Control.Monad.Cont.Class (
import Control.Monad.Trans.Cont (ContT)
import qualified Control.Monad.Trans.Cont as ContT
import Control.Monad.Trans.Error as Error
import Control.Monad.Trans.Except as Except
import Control.Monad.Trans.Identity as Identity
import Control.Monad.Trans.List as List
import Control.Monad.Trans.Maybe as Maybe
import Control.Monad.Trans.Reader as Reader
import Control.Monad.Trans.RWS.Lazy as LazyRWS
......@@ -82,9 +80,9 @@ class Monad m => MonadCont m where
Provides an escape continuation mechanism for use with Continuation monads.
Escape continuations allow to abort the current computation and return
a value immediately.
They achieve a similar effect to 'Control.Monad.Error.throwError'
and 'Control.Monad.Error.catchError'
within an 'Control.Monad.Error.Error' monad.
They achieve a similar effect to 'Control.Monad.Error.Class.throwError'
and 'Control.Monad.Error.Class.catchError'
within an 'Control.Monad.Except.Except' monad.
Advantage of this function over calling @return@ is that it makes
the continuation explicit,
allowing more flexibility and better control
......@@ -106,9 +104,6 @@ instance MonadCont (ContT r m) where
-- ---------------------------------------------------------------------------
-- Instances for other mtl transformers
instance (Error e, MonadCont m) => MonadCont (ErrorT e m) where
callCC = Error.liftCallCC callCC
{- | @since 2.2 -}
instance MonadCont m => MonadCont (ExceptT e m) where
callCC = Except.liftCallCC callCC
......@@ -116,9 +111,6 @@ instance MonadCont m => MonadCont (ExceptT e m) where
instance MonadCont m => MonadCont (IdentityT m) where
callCC = Identity.liftCallCC callCC
instance MonadCont m => MonadCont (ListT m) where
callCC = List.liftCallCC callCC
instance MonadCont m => MonadCont (MaybeT m) where
callCC = Maybe.liftCallCC callCC
......
{-# LANGUAGE CPP #-}
{- |
Module : Control.Monad.Error
Copyright : (c) Michael Weber <michael.weber@post.rwth-aachen.de> 2001,
(c) Jeff Newbern 2003-2006,
(c) Andriy Palamarchuk 2006
License : BSD-style (see the file LICENSE)
Maintainer : libraries@haskell.org
Stability : experimental
Portability : non-portable (multi-parameter type classes)
[Computation type:] Computations which may fail or throw exceptions.
[Binding strategy:] Failure records information about the cause\/location
of the failure. Failure values bypass the bound function,
other values are used as inputs to the bound function.
[Useful for:] Building computations from sequences of functions that may fail
or using exception handling to structure error handling.
[Zero and plus:] Zero is represented by an empty error and the plus operation
executes its second argument if the first fails.
[Example type:] @'Either' String a@
The Error monad (also called the Exception monad).
-}
{-
Rendered by Michael Weber <mailto:michael.weber@post.rwth-aachen.de>,
inspired by the Haskell Monad Template Library from
Andy Gill (<http://web.cecs.pdx.edu/~andy/>)
-}
module Control.Monad.Error
{-# DEPRECATED "Use \"Control.Monad.Except\" instead" #-} (
-- * Monads with error handling
MonadError(..),
Error(..),
-- * The ErrorT monad transformer
ErrorT(ErrorT),
runErrorT,
mapErrorT,
module Control.Monad,
module Control.Monad.Fix,
module Control.Monad.Trans,
-- * Example 1: Custom Error Data Type
-- $customErrorExample
-- * Example 2: Using ErrorT Monad Transformer
-- $ErrorTExample
) where
import Control.Monad.Error.Class
import Control.Monad.Trans
import Control.Monad.Trans.Error (ErrorT(ErrorT), runErrorT, mapErrorT)
import Control.Monad
import Control.Monad.Fix
#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ < 707
import Control.Monad.Instances ()
#endif
{- $customErrorExample
Here is an example that demonstrates the use of a custom 'Error' data type with
the 'throwError' and 'catchError' exception mechanism from 'MonadError'.
The example throws an exception if the user enters an empty string
or a string longer than 5 characters. Otherwise it prints length of the string.
>-- This is the type to represent length calculation error.
>data LengthError = EmptyString -- Entered string was empty.
> | StringTooLong Int -- A string is longer than 5 characters.
> -- Records a length of the string.
> | OtherError String -- Other error, stores the problem description.
>
>-- We make LengthError an instance of the Error class
>-- to be able to throw it as an exception.
>instance Error LengthError where
> noMsg = OtherError "A String Error!"
> strMsg s = OtherError s
>
>-- Converts LengthError to a readable message.
>instance Show LengthError where
> show EmptyString = "The string was empty!"
> show (StringTooLong len) =
> "The length of the string (" ++ (show len) ++ ") is bigger than 5!"
> show (OtherError msg) = msg
>
>-- For our monad type constructor, we use Either LengthError
>-- which represents failure using Left LengthError
>-- or a successful result of type a using Right a.
>type LengthMonad = Either LengthError
>
>main = do
> putStrLn "Please enter a string:"
> s <- getLine
> reportResult (calculateLength s)
>
>-- Wraps length calculation to catch the errors.
>-- Returns either length of the string or an error.
>calculateLength :: String -> LengthMonad Int
>calculateLength s = (calculateLengthOrFail s) `catchError` Left
>
>-- Attempts to calculate length and throws an error if the provided string is
>-- empty or longer than 5 characters.
>-- The processing is done in Either monad.
>calculateLengthOrFail :: String -> LengthMonad Int
>calculateLengthOrFail [] = throwError EmptyString
>calculateLengthOrFail s | len > 5 = throwError (StringTooLong len)
> | otherwise = return len
> where len = length s
>
>-- Prints result of the string length calculation.
>reportResult :: LengthMonad Int -> IO ()
>reportResult (Right len) = putStrLn ("The length of the string is " ++ (show len))
>reportResult (Left e) = putStrLn ("Length calculation failed with error: " ++ (show e))
-}
{- $ErrorTExample
@'ErrorT'@ monad transformer can be used to add error handling to another monad.
Here is an example how to combine it with an @IO@ monad:
>import Control.Monad.Error
>
>-- An IO monad which can return String failure.
>-- It is convenient to define the monad type of the combined monad,
>-- especially if we combine more monad transformers.
>type LengthMonad = ErrorT String IO
>
>main = do
> -- runErrorT removes the ErrorT wrapper
> r <- runErrorT calculateLength
> reportResult r
>
>-- Asks user for a non-empty string and returns its length.
>-- Throws an error if user enters an empty string.
>calculateLength :: LengthMonad Int
>calculateLength = do
> -- all the IO operations have to be lifted to the IO monad in the monad stack
> liftIO $ putStrLn "Please enter a non-empty string: "
> s <- liftIO getLine
> if null s
> then throwError "The string was empty!"
> else return $ length s
>
>-- Prints result of the string length calculation.
>reportResult :: Either String Int -> IO ()
>reportResult (Right len) = putStrLn ("The length of the string is " ++ (show len))
>reportResult (Left e) = putStrLn ("Length calculation failed with error: " ++ (show e))
-}
......@@ -39,7 +39,6 @@ The Error monad (also called the Exception monad).
Andy Gill (<http://web.cecs.pdx.edu/~andy/>)
-}
module Control.Monad.Error.Class (
Error(..),
MonadError(..),
liftEither,
tryError,
......@@ -50,11 +49,8 @@ module Control.Monad.Error.Class (
import qualified Control.Exception
import Control.Monad.Trans.Except (Except, ExceptT)
import Control.Monad.Trans.Error (Error(..), ErrorT)
import qualified Control.Monad.Trans.Except as ExceptT (throwE, catchE)
import qualified Control.Monad.Trans.Error as ErrorT (throwError, catchError)
import Control.Monad.Trans.Identity as Identity
import Control.Monad.Trans.List as List
import Control.Monad.Trans.Maybe as Maybe
import Control.Monad.Trans.Reader as Reader
import Control.Monad.Trans.RWS.Lazy as LazyRWS
......@@ -146,10 +142,6 @@ instance MonadError e (Either e) where
Left l `catchError` h = h l
Right r `catchError` _ = Right r
instance (Monad m, Error e) => MonadError e (ErrorT e m) where
throwError = ErrorT.throwError
catchError = ErrorT.catchError
{- | @since 2.2 -}
instance Monad m => MonadError e (ExceptT e m) where
throwError = ExceptT.throwE
......@@ -165,10 +157,6 @@ instance MonadError e m => MonadError e (IdentityT m) where
throwError = lift . throwError
catchError = Identity.liftCatch catchError
instance MonadError e m => MonadError e (ListT m) where
throwError = lift . throwError
catchError = List.liftCatch catchError
instance MonadError e m => MonadError e (MaybeT m) where
throwError = lift . throwError
catchError = Maybe.liftCatch catchError
......
-----------------------------------------------------------------------------
-- |
-- Module : Control.Monad.List
-- Copyright : (c) Andy Gill 2001,
-- (c) Oregon Graduate Institute of Science and Technology, 2001
-- License : BSD-style (see the file LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : experimental
-- Portability : portable
--
-- The List monad.
--
-----------------------------------------------------------------------------
module Control.Monad.List (
ListT(..),
mapListT,
module Control.Monad,
module Control.Monad.Trans,
) where
import Control.Monad
import Control.Monad.Trans
import Control.Monad.Trans.List
......@@ -36,7 +36,6 @@ import Control.Monad.State.Class
import Control.Monad.Writer.Class
import Control.Monad.Trans.Class
import Control.Monad.Trans.Error(Error, ErrorT)
import Control.Monad.Trans.Except(ExceptT)
import Control.Monad.Trans.Maybe(MaybeT)
import Control.Monad.Trans.Identity(IdentityT)
......@@ -68,6 +67,5 @@ instance (Monoid w, Monad m) => MonadRWS r w s (Strict.RWST r w s m)
-- | @since 2.2
instance MonadRWS r w s m => MonadRWS r w s (ExceptT e m)
instance (Error e, MonadRWS r w s m) => MonadRWS r w s (ErrorT e m)
instance MonadRWS r w s m => MonadRWS r w s (IdentityT m)
instance MonadRWS r w s m => MonadRWS r w s (MaybeT m)
......@@ -48,9 +48,7 @@ module Control.Monad.Reader.Class (
import Control.Monad.Trans.Cont as Cont
import Control.Monad.Trans.Except
import Control.Monad.Trans.Error
import Control.Monad.Trans.Identity
import Control.Monad.Trans.List
import Control.Monad.Trans.Maybe
import Control.Monad.Trans.Reader (ReaderT)
import qualified Control.Monad.Trans.Reader as ReaderT (ask, local, reader)
......@@ -145,11 +143,6 @@ instance MonadReader r' m => MonadReader r' (ContT r m) where
local = Cont.liftLocal ask local
reader = lift . reader
instance (Error e, MonadReader r m) => MonadReader r (ErrorT e m) where
ask = lift ask
local = mapErrorT . local
reader = lift . reader
{- | @since 2.2 -}
instance MonadReader r m => MonadReader r (ExceptT e m) where
ask = lift ask
......@@ -161,11 +154,6 @@ instance MonadReader r m => MonadReader r (IdentityT m) where
local = mapIdentityT . local
reader = lift . reader
instance MonadReader r m => MonadReader r (ListT m) where
ask = lift ask
local = mapListT . local
reader = lift . reader
instance MonadReader r m => MonadReader r (MaybeT m) where
ask = lift ask
local = mapMaybeT . local
......
......@@ -33,10 +33,8 @@ module Control.Monad.State.Class (
) where
import Control.Monad.Trans.Cont
import Control.Monad.Trans.Error
import Control.Monad.Trans.Except
import Control.Monad.Trans.Identity
import Control.Monad.Trans.List
import Control.Monad.Trans.Maybe
import Control.Monad.Trans.Reader
import qualified Control.Monad.Trans.RWS.Lazy as LazyRWS (RWST, get, put, state)
......@@ -147,11 +145,6 @@ instance MonadState s m => MonadState s (ContT r m) where
put = lift . put
state = lift . state
instance (Error e, MonadState s m) => MonadState s (ErrorT e m) where
get = lift get
put = lift . put
state = lift . state
-- | @since 2.2
instance MonadState s m => MonadState s (ExceptT e m) where
get = lift get
......@@ -163,11 +156,6 @@ instance MonadState s m => MonadState s (IdentityT m) where
put = lift . put
state = lift . state
instance MonadState s m => MonadState s (ListT m) where
get = lift get
put = lift . put
state = lift . state
instance MonadState s m => MonadState s (MaybeT m) where
get = lift get
put = lift . put
......
......@@ -30,7 +30,6 @@ module Control.Monad.Writer.Class (
censor,
) where
import Control.Monad.Trans.Error as Error
import Control.Monad.Trans.Except as Except
import Control.Monad.Trans.Identity as Identity
import Control.Monad.Trans.Maybe as Maybe
......@@ -169,12 +168,6 @@ instance (Monoid w, Monad m) => MonadWriter w (StrictRWS.RWST r w s m) where
-- All of these instances need UndecidableInstances,
-- because they do not satisfy the coverage condition.
instance (Error e, MonadWriter w m) => MonadWriter w (ErrorT e m) where
writer = lift . writer
tell = lift . tell
listen = Error.liftListen listen
pass = Error.liftPass pass
-- | @since 2.2
instance MonadWriter w m => MonadWriter w (ExceptT e m) where
writer = lift . writer
......
......@@ -37,11 +37,9 @@ Library
exposed-modules:
Control.Monad.Cont
Control.Monad.Cont.Class
Control.Monad.Error
Control.Monad.Error.Class
Control.Monad.Except
Control.Monad.Identity
Control.Monad.List
Control.Monad.RWS
Control.Monad.RWS.Class
Control.Monad.RWS.CPS
......
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