transformers 0.6.1.0 → 0.6.3.0

raw patch · 26 files changed

Files

• Control/Applicative/Backwards.hs +1/−1
• Control/Applicative/Lift.hs +1/−1
• Control/Monad/Signatures.hs +8/−4
• Control/Monad/Trans/Accum.hs +44/−24
• Control/Monad/Trans/Class.hs +9/−6
• Control/Monad/Trans/Cont.hs +3/−1
• Control/Monad/Trans/Except.hs +23/−14
• Control/Monad/Trans/Identity.hs +1/−1
• Control/Monad/Trans/Maybe.hs +3/−3
• Control/Monad/Trans/RWS/CPS.hs +3/−0
• Control/Monad/Trans/RWS/Lazy.hs +3/−0
• Control/Monad/Trans/RWS/Strict.hs +3/−0
• Control/Monad/Trans/Reader.hs +13/−5
• Control/Monad/Trans/Select.hs +8/−10
• Control/Monad/Trans/State/Lazy.hs +17/−0
• Control/Monad/Trans/State/Strict.hs +3/−0
• Control/Monad/Trans/Writer/CPS.hs +18/−7
• Control/Monad/Trans/Writer/Lazy.hs +19/−5
• Control/Monad/Trans/Writer/Strict.hs +19/−5
• Data/Functor/Constant.hs +1/−1
• Data/Functor/Reverse.hs +1/−1
• changelog +16/−0
• images/bind-AccumT.svg +66/−0
• images/bind-ReaderT.svg +57/−0
• images/bind-WriterT.svg +60/−0
• transformers.cabal +9/−6

@@ -41,7 +41,7 @@ import Prelude hiding (foldr, foldr1, foldl, foldl1, null, length) import Control.Applicative import Data.Foldable-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Traversable (Traversable(traverse, sequenceA)) #endif 

@@ -39,7 +39,7 @@  import Control.Applicative import Data.Functor.Constant-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Foldable (Foldable(foldMap)) import Data.Monoid (Monoid(..)) import Data.Traversable (Traversable(traverse))

@@ -27,23 +27,27 @@ -- introduced in "Control.Monad.Trans.Cont". -- Any lifting function @liftCallCC@ should satisfy ----- * @'Control.Monad.Trans.Class.lift' (f k) = f' ('Control.Monad.Trans.Class.lift' . k) => 'Control.Monad.Trans.Class.lift' (cf f) = liftCallCC cf f'@+-- @'Control.Monad.Trans.Class.lift' (f k) = f' ('Control.Monad.Trans.Class.lift' . k) => 'Control.Monad.Trans.Class.lift' (cf f) = liftCallCC cf f'@ --+-- This implies that on entry to the continuation any outer monad+-- transformer effect inside @callCC@ will have been rolled back. type CallCC m a b = ((a -> m b) -> m a) -> m a  -- | Signature of the @catchE@ operation, -- introduced in "Control.Monad.Trans.Except". -- Any lifting function @liftCatch@ should satisfy ----- * @'Control.Monad.Trans.Class.lift' (cf m f) = liftCatch ('Control.Monad.Trans.Class.lift' . cf) ('Control.Monad.Trans.Class.lift' f)@+-- @'Control.Monad.Trans.Class.lift' (cf m h) = liftCatch cf ('Control.Monad.Trans.Class.lift' m) ('Control.Monad.Trans.Class.lift' . h)@ --+-- This implies that on entry to the handler function any outer monad+-- transformer effect inside @catchE@ will have been rolled back. type Catch e m a = m a -> (e -> m a) -> m a  -- | Signature of the @listen@ operation, -- introduced in "Control.Monad.Trans.Writer". -- Any lifting function @liftListen@ should satisfy ----- * @'Control.Monad.Trans.Class.lift' . liftListen = liftListen . 'Control.Monad.Trans.Class.lift'@+-- @'Control.Monad.Trans.Class.lift' . liftListen = liftListen . 'Control.Monad.Trans.Class.lift'@ -- type Listen w m a = m a -> m (a, w) @@ -51,6 +55,6 @@ -- introduced in "Control.Monad.Trans.Writer". -- Any lifting function @liftPass@ should satisfy ----- * @'Control.Monad.Trans.Class.lift' . liftPass = liftPass . 'Control.Monad.Trans.Class.lift'@+-- @'Control.Monad.Trans.Class.lift' . liftPass = liftPass . 'Control.Monad.Trans.Class.lift'@ -- type Pass w m a =  m (a, w -> w) -> m a

@@ -18,10 +18,12 @@ -- -- The lazy 'AccumT' monad transformer, which adds accumulation -- capabilities (such as declarations or document patches) to a given monad.+-- Each computation has access to the combination of the input environment+-- and outputs added so far, and returns the outputs added. ----- This monad transformer provides append-only accumulation--- during the computation. For more general access, use--- "Control.Monad.Trans.State" instead.+-- In applications requiring only the ability to accumulate an output and+-- to inspect the output so far, it would be considerably more efficient+-- to use "Control.Monad.Trans.State" instead. -----------------------------------------------------------------------------  module Control.Monad.Trans.Accum (@@ -33,8 +35,7 @@     evalAccum,     mapAccum,     -- * The AccumT monad transformer-    AccumT(AccumT),-    runAccumT,+    AccumT(..),     execAccumT,     evalAccumT,     mapAccumT,@@ -76,10 +77,19 @@ #endif  -- ------------------------------------------------------------------------------ | An accumulation monad parameterized by the type @w@ of output to accumulate.+-- | An accumulation monad (non-strict) parameterized by the type @w@+-- of output to accumulate. ----- The 'return' function produces the output 'mempty', while @>>=@--- combines the outputs of the subcomputations using 'mappend'.+-- This monad is a more complex extension of both the reader and writer+-- monads.  The 'return' function produces the output 'mempty', while @m+-- '>>=' k@ uses the output of @m@ both to extend the initial environment+-- of @k@ and to combine with the output of @k@:+--+-- <<images/bind-AccumT.svg>>+--+-- In applications requiring only the ability to accumulate an output and+-- to inspect the output so far, it would be considerably more efficient+-- to use a state monad. type Accum w = AccumT w Identity  -- | Construct an accumulation computation from a (result, output) pair.@@ -124,25 +134,32 @@ -- --   * @m@ - The inner monad. ----- The 'return' function produces the output 'mempty', while @>>=@--- combines the outputs of the subcomputations using 'mappend'.+-- This monad transformer is a more complex extension of both the reader+-- and writer monad transformers.  The 'return' function produces the+-- output 'mempty', while @m '>>=' k@ uses the output of @m@ both to+-- extend the initial environment of @k@ and to combine with the output+-- of @k@: ----- This monad transformer is similar to both state and writer monad transformers.--- Thus it can be seen as+-- <<images/bind-AccumT.svg>> -----  * a restricted append-only version of a state monad transformer or+-- In applications requiring only the ability to accumulate an output and+-- to inspect the output so far, it would be considerably more efficient+-- to use a state monad transformer. -----  * a writer monad transformer with the extra ability to read all previous output.-newtype AccumT w m a = AccumT (w -> m (a, w))+-- @AccumT w m@ is strict if and only if @m@ is.+newtype AccumT w m a = AccumT {+    -- | Unwrap an accumulation computation.  For example, in the call+    --+    -- @    (value, locals) <- runAccumT action globals@+    --+    -- the action is fed an initial environment @globals@, and @locals@ is+    -- the sum of all arguments to calls of 'add' executed by the action.+    runAccumT :: w -> m (a, w)+    } #if __GLASGOW_HASKELL__ >= 704     deriving (Generic) #endif --- | Unwrap an accumulation computation.-runAccumT :: AccumT w m a -> w -> m (a, w)-runAccumT (AccumT f) = f-{-# INLINE runAccumT #-}- -- | Extract the output from an accumulation computation. -- -- * @'execAccumT' m w = 'liftM' 'snd' ('runAccumT' m w)@@@ -152,8 +169,8 @@     return w' {-# INLINE execAccumT #-} --- | Evaluate an accumulation computation with the given initial output history--- and return the final value, discarding the final output.+-- | Evaluate an accumulation computation with the given initial output+-- history and return the final value, discarding the final output. -- -- * @'evalAccumT' m w = 'liftM' 'fst' ('runAccumT' m w)@ evalAccumT :: (Monad m, Monoid w) => AccumT w m a -> w -> m a@@ -162,8 +179,8 @@     return a {-# INLINE evalAccumT #-} --- | Map both the return value and output of a computation using--- the given function.+-- | Map both the return value and output of a computation using the+-- given function. -- -- * @'runAccumT' ('mapAccumT' f m) = f . 'runAccumT' m@ mapAccumT :: (m (a, w) -> n (b, w)) -> AccumT w m a -> AccumT w n b@@ -262,6 +279,9 @@ {-# INLINE liftCallCC' #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @catchE@ discards any output from the body on entering+-- the handler. liftCatch :: Catch e m (a, w) -> Catch e (AccumT w m) a liftCatch catchE m h =     AccumT $ \ w -> runAccumT m w `catchE` \ e -> runAccumT (h e) w

@@ -87,15 +87,18 @@     lift :: (Monad m) => m a -> t m a  {- $conventions-Most monad transformer modules include the special case of applying-the transformer to 'Data.Functor.Identity.Identity'.  For example,+All monad transformer modules except 'Control.Monad.Trans.Maybe'+include the special case of applying the transformer+to 'Data.Functor.Identity.Identity'.  For example, @'Control.Monad.Trans.State.Lazy.State' s@ is an abbreviation for @'Control.Monad.Trans.State.Lazy.StateT' s 'Data.Functor.Identity.Identity'@.+As a consequence, operations defined on the monad transformer can also+be used on this special case.  Each monad transformer also comes with an operation @run@/XXX/@T@ to unwrap the transformer, exposing a computation of the inner monad.-(Currently these functions are defined as field labels, but in the next-major release they will be separate functions.)+(Currently these functions are defined as field labels, but in a future+major release they may be separate functions.)  All of the monad transformers except 'Control.Monad.Trans.Cont.ContT' and 'Control.Monad.Trans.Cont.SelectT' are functors on the category@@ -134,7 +137,7 @@ >>> undefined >> print 2 *** Exception: Prelude.undefined -However the monads 'Data.Functor.Identity.Identity' and @(->) a@ are not:+However, the monads 'Data.Functor.Identity.Identity' and @(->) a@ are not:  >>> undefined >> Identity 2 Identity 2@@ -143,7 +146,7 @@  In a strict monad you know when each action is executed, but the monad is not necessarily strict in the return value, or in other components-of the monad, such as a state.  However you can use 'seq' to create+of the monad, such as a state.  However, you can use 'seq' to create an action that is strict in the component you want evaluated. -} 

@@ -64,7 +64,7 @@ #endif  {- |-Continuation monad.+The continuation monad, which is non-strict. @Cont r a@ is a CPS ("continuation-passing style") computation that produces an intermediate result of type @a@ within a CPS computation whose final result type is @r@.@@ -139,6 +139,8 @@ -- -- 'ContT' is not a functor on the category of monads, and many operations -- cannot be lifted through it.+--+-- @ContT r m@ is strict if and only if @m@ is. newtype ContT r m a = ContT { runContT :: (a -> m r) -> m r } #if __GLASGOW_HASKELL__ >= 704     deriving (Generic)

@@ -16,7 +16,8 @@ -- Stability   :  experimental -- Portability :  portable ----- This monad transformer extends a monad with the ability to throw exceptions.+-- This monad transformer extends a monad with the ability to throw+-- and catch exceptions. -- -- A sequence of actions terminates normally, producing a value, -- only if none of the actions in the sequence throws an exception.@@ -35,8 +36,7 @@     mapExcept,     withExcept,     -- * The ExceptT monad transformer-    ExceptT(ExceptT),-    runExceptT,+    ExceptT(..),     mapExceptT,     withExceptT,     -- * Exception operations@@ -45,6 +45,7 @@     handleE,     tryE,     finallyE,+    onE,     -- * Lifting other operations     liftCallCC,     liftListen,@@ -69,7 +70,7 @@ #if MIN_VERSION_base(4,4,0) import Control.Monad.Zip (MonadZip(mzipWith)) #endif-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Foldable (Foldable(foldMap)) import Data.Monoid (Monoid(mempty, mappend)) import Data.Traversable (Traversable(traverse))@@ -78,9 +79,11 @@ import GHC.Generics #endif --- | The parameterizable exception monad.+-- | The parameterizable exception monad, which is strict. ----- Computations are either exceptions or normal values.+-- Computations are either exceptions (of any type) or normal values.+-- These computations are plain values, and are unrelated to the+-- "Control.Exception" mechanism, which is tied to the 'IO' monad. -- -- The 'return' function returns a normal value, while @>>=@ exits on -- the first exception.  For a variant that continues after an error@@ -116,16 +119,19 @@  -- | A monad transformer that adds exceptions to other monads. ----- @ExceptT@ constructs a monad parameterized over two things:+-- @ExceptT@ constructs a strict monad parameterized over two things: ----- * e - The exception type.+-- * e - An arbitrary exception type. -- -- * m - The inner monad. --+-- The monadic computations are a plain values.  They are unrelated to+-- the "Control.Exception" mechanism, which is tied to the 'IO' monad.+-- -- The 'return' function yields a computation that produces the given -- value, while @>>=@ sequences two subcomputations, exiting on the -- first exception.-newtype ExceptT e m a = ExceptT (m (Either e a))+newtype ExceptT e m a = ExceptT { runExceptT :: m (Either e a) } #if __GLASGOW_HASKELL__ >= 710     deriving (Generic, Generic1) #elif __GLASGOW_HASKELL__ >= 704@@ -164,11 +170,6 @@ instance (Show e, Show1 m, Show a) => Show (ExceptT e m a) where     showsPrec = showsPrec1 --- | The inverse of 'ExceptT'.-runExceptT :: ExceptT e m a -> m (Either e a)-runExceptT (ExceptT m) = m-{-# INLINE runExceptT #-}- -- | Map the unwrapped computation using the given function. -- -- * @'runExceptT' ('mapExceptT' f m) = f ('runExceptT' m)@@@ -328,6 +329,14 @@     closer     either throwE return res {-# INLINE finallyE #-}++-- | If the first action succeeds, return its value, ignoring the+-- second action.  If the first action throws an exception, run the+-- second action and then throw an exception, either the one thrown by+-- the second action, if any, or the one thrown by the first action.+onE :: (Monad m) => ExceptT e m a -> ExceptT e m b -> ExceptT e m a+onE action1 action2 = action1 `catchE` \ e -> action2 >> throwE e+{-# INLINE onE #-}  -- | Lift a @callCC@ operation to the new monad. liftCallCC :: CallCC m (Either e a) (Either e b) -> CallCC (ExceptT e m) a b

@@ -54,7 +54,7 @@ import Control.Monad.Zip (MonadZip(mzipWith)) #endif import Data.Foldable-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Traversable (Traversable(traverse)) #endif import Prelude hiding (foldr, foldr1, foldl, foldl1, null, length)

@@ -61,7 +61,7 @@ import Control.Monad.Zip (MonadZip(mzipWith)) #endif import Data.Maybe (fromMaybe)-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Foldable (Foldable(foldMap)) import Data.Traversable (Traversable(traverse)) #endif@@ -69,8 +69,8 @@ import GHC.Generics #endif --- | The parameterizable maybe monad, obtained by composing an arbitrary--- monad with the 'Maybe' monad.+-- | The parameterizable maybe monad, a strict monad obtained by composing+-- an arbitrary monad with the 'Maybe' monad. -- -- Computations are actions that may produce a value or exit. --

@@ -409,6 +409,9 @@ {-# INLINE liftCallCC' #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @catchE@ discards any output or changes to the state from+-- the body on entering the handler. liftCatch :: Catch e m (a,s,w) -> Catch e (RWST r w s m) a liftCatch catchE m h =     RWST $ \ r s w -> unRWST m r s w `catchE` \ e -> unRWST (h e) r s w

@@ -393,6 +393,9 @@ {-# INLINE liftCallCC' #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @catchE@ discards any output or changes to the state from+-- the body on entering the handler. liftCatch :: Catch e m (a,s,w) -> Catch e (RWST r w s m) a liftCatch catchE m h =     RWST $ \ r s -> runRWST m r s `catchE` \ e -> runRWST (h e) r s

@@ -397,6 +397,9 @@ {-# INLINE liftCallCC' #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @catchE@ discards any output or changes to the state from+-- the body on entering the handler. liftCatch :: Catch e m (a,s,w) -> Catch e (RWST r w s m) a liftCatch catchE m h =     RWST $ \ r s -> runRWST m r s `catchE` \ e -> runRWST (h e) r s

@@ -71,12 +71,15 @@ import GHC.Generics #endif --- | The parameterizable reader monad.+-- | The parameterizable reader monad, which is non-strict. -- -- Computations are functions of a shared environment. ----- The 'return' function ignores the environment, while @>>=@ passes--- the inherited environment to both subcomputations.+-- The 'return' function ignores the environment, while @m '>>=' k@+-- passes the inherited environment to both subcomputations:+--+-- <<images/bind-ReaderT.svg>>+-- type Reader r = ReaderT r Identity  -- | Constructor for computations in the reader monad (equivalent to 'asks').@@ -114,8 +117,13 @@ -- | The reader monad transformer, -- which adds a read-only environment to the given monad. ----- The 'return' function ignores the environment, while @>>=@ passes--- the inherited environment to both subcomputations.+-- The 'return' function ignores the environment, while @m '>>=' k@+-- passes the inherited environment to both subcomputations:+--+-- <<images/bind-ReaderT.svg>>+--+--+-- @ReaderT r m@ is strict if and only if @m@ is. newtype ReaderT r m a = ReaderT { runReaderT :: r -> m a } #if __GLASGOW_HASKELL__ >= 710     deriving (Generic, Generic1)

@@ -37,8 +37,7 @@     runSelect,     mapSelect,     -- * The SelectT monad transformer-    SelectT(SelectT),-    runSelectT,+    SelectT(..),     mapSelectT,     -- * Monad transformation     selectToContT,@@ -58,7 +57,7 @@ import GHC.Generics #endif --- | Selection monad.+-- | The selection monad, which is non-strict. type Select r = SelectT r Identity  -- | Constructor for computations in the selection monad.@@ -83,16 +82,15 @@ -- -- 'SelectT' is not a functor on the category of monads, and many operations -- cannot be lifted through it.-newtype SelectT r m a = SelectT ((a -> m r) -> m a)+--+-- @SelectT r m@ is strict if and only if @m@ is.+newtype SelectT r m a = SelectT {+    -- | Runs a @SelectT@ computation with a function for evaluating+    -- answers to select a particular answer.+    runSelectT :: (a -> m r) -> m a } #if __GLASGOW_HASKELL__ >= 704     deriving (Generic) #endif---- | Runs a @SelectT@ computation with a function for evaluating answers--- to select a particular answer.  (The inverse of 'select'.)-runSelectT :: SelectT r m a -> (a -> m r) -> m a-runSelectT (SelectT g) = g-{-# INLINE runSelectT #-}  -- | Apply a function to transform the result of a selection computation. -- This has a more restricted type than the @map@ operations for other

@@ -64,6 +64,9 @@     liftCatch,     liftListen,     liftPass,+    -- * Conversion to and from the strict version+    strictToLazyStateT,+    lazyToStrictStateT,     -- * Examples     -- ** State monads     -- $examples@@ -78,6 +81,7 @@ import Control.Monad.IO.Class import Control.Monad.Signatures import Control.Monad.Trans.Class+import qualified Control.Monad.Trans.State.Strict as Strict #if MIN_VERSION_base(4,12,0) import Data.Functor.Contravariant #endif@@ -336,6 +340,9 @@ {-# INLINE liftCallCC' #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies+-- that the lifted @catchE@ rolls back to the original state on entering+-- the handler. liftCatch :: Catch e m (a,s) -> Catch e (StateT s m) a liftCatch catchE m h =     StateT $ \ s -> runStateT m s `catchE` \ e -> runStateT (h e) s@@ -354,6 +361,16 @@     ~((a, f), s') <- runStateT m s     return ((a, s'), f) {-# INLINE liftPass #-}++-- | Convert from the strict version to the lazy version+strictToLazyStateT :: Strict.StateT s m a -> StateT s m a+strictToLazyStateT (Strict.StateT f) = StateT f+{-# INLINE strictToLazyStateT #-}++-- | Convert from the lazy version to the strict version+lazyToStrictStateT :: StateT s m a -> Strict.StateT s m a+lazyToStrictStateT (StateT f) = Strict.StateT f+{-# INLINE lazyToStrictStateT #-}  {- $examples 

@@ -337,6 +337,9 @@ {-# INLINE liftCallCC' #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies+-- that the lifted @catchE@ rolls back to the original state on entering+-- the handler. liftCatch :: Catch e m (a,s) -> Catch e (StateT s m) a liftCatch catchE m h =     StateT $ \ s -> runStateT m s `catchE` \ e -> runStateT (h e) s

@@ -76,8 +76,12 @@ -- --------------------------------------------------------------------------- -- | A writer monad parameterized by the type @w@ of output to accumulate. ----- The 'return' function produces the output 'mempty', while '>>='--- combines the outputs of the subcomputations using 'mappend'.+-- The 'return' function produces the output 'mempty', while @m '>>=' k@+-- combines the outputs of the subcomputations using 'mappend' (also+-- known as @<>@):+--+-- <<images/bind-WriterT.svg>>+-- type Writer w = WriterT w Identity  -- | Construct a writer computation from a (result, output) pair.@@ -116,9 +120,12 @@ -- --   * @m@ - The inner monad. ----- The 'return' function produces the output 'mempty', while '>>='--- combines the outputs of the subcomputations using 'mappend'.-+-- The 'return' function produces the output 'mempty', while @m '>>=' k@+-- combines the outputs of the subcomputations using 'mappend' (also+-- known as @<>@):+--+-- <<images/bind-WriterT.svg>>+-- newtype WriterT w m a = WriterT { unWriterT :: w -> m (a, w) } #if __GLASGOW_HASKELL__ >= 704     deriving (Generic)@@ -276,14 +283,18 @@ {-# INLINE censor #-}  -- | Uniform lifting of a @callCC@ operation to the new monad.--- This version rolls back to the original state on entering the--- continuation.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @callCC@ discards any output from the body on entering+-- the saved continuation. liftCallCC :: CallCC m (a, w) (b, w) -> CallCC (WriterT w m) a b liftCallCC callCC f = WriterT $ \ w ->     callCC $ \ c -> unWriterT (f (\ a -> WriterT $ \ _ -> c (a, w))) w {-# INLINE liftCallCC #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @catchE@ discards any output from the body on entering+-- the handler. liftCatch :: Catch e m (a, w) -> Catch e (WriterT w m) a liftCatch catchE m h = WriterT $ \ w ->     unWriterT m w `catchE` \ e -> unWriterT (h e) w

@@ -70,7 +70,7 @@ #endif import Data.Foldable import Data.Monoid-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Traversable (Traversable(traverse)) #endif import Prelude hiding (null, length)@@ -81,8 +81,12 @@ -- --------------------------------------------------------------------------- -- | A writer monad parameterized by the type @w@ of output to accumulate. ----- The 'return' function produces the output 'mempty', while @>>=@--- combines the outputs of the subcomputations using 'mappend'.+-- The 'return' function produces the output 'mempty', while @m '>>=' k@+-- combines the outputs of the subcomputations using 'mappend' (also+-- known as @<>@):+--+-- <<images/bind-WriterT.svg>>+-- type Writer w = WriterT w Identity  -- | Construct a writer computation from a (result, output) pair.@@ -119,8 +123,12 @@ -- --   * @m@ - The inner monad. ----- The 'return' function produces the output 'mempty', while @>>=@--- combines the outputs of the subcomputations using 'mappend'.+-- The 'return' function produces the output 'mempty', while @m '>>=' k@+-- combines the outputs of the subcomputations using 'mappend' (also+-- known as @<>@):+--+-- <<images/bind-WriterT.svg>>+-- newtype WriterT w m a = WriterT { runWriterT :: m (a, w) } #if __GLASGOW_HASKELL__ >= 704     deriving (Generic)@@ -309,6 +317,9 @@ {-# INLINE censor #-}  -- | Lift a @callCC@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @callCC@ discards any output from the body on entering+-- the saved condinuation. liftCallCC :: (Monoid w) => CallCC m (a,w) (b,w) -> CallCC (WriterT w m) a b liftCallCC callCC f = WriterT $     callCC $ \ c ->@@ -316,6 +327,9 @@ {-# INLINE liftCallCC #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @catchE@ discards any output from the body on entering+-- the handler. liftCatch :: Catch e m (a,w) -> Catch e (WriterT w m) a liftCatch catchE m h =     WriterT $ runWriterT m `catchE` \ e -> runWriterT (h e)

@@ -73,7 +73,7 @@ #endif import Data.Foldable import Data.Monoid-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Traversable (Traversable(traverse)) #endif import Prelude hiding (null, length)@@ -84,8 +84,12 @@ -- --------------------------------------------------------------------------- -- | A writer monad parameterized by the type @w@ of output to accumulate. ----- The 'return' function produces the output 'mempty', while @>>=@--- combines the outputs of the subcomputations using 'mappend'.+-- The 'return' function produces the output 'mempty', while @m '>>=' k@+-- combines the outputs of the subcomputations using 'mappend' (also+-- known as @<>@):+--+-- <<images/bind-WriterT.svg>>+-- type Writer w = WriterT w Identity  -- | Construct a writer computation from a (result, output) pair.@@ -122,8 +126,12 @@ -- --   * @m@ - The inner monad. ----- The 'return' function produces the output 'mempty', while @>>=@--- combines the outputs of the subcomputations using 'mappend'.+-- The 'return' function produces the output 'mempty', while @m '>>=' k@+-- combines the outputs of the subcomputations using 'mappend' (also+-- known as @<>@):+--+-- <<images/bind-WriterT.svg>>+-- newtype WriterT w m a = WriterT { runWriterT :: m (a, w) } #if __GLASGOW_HASKELL__ >= 704     deriving (Generic)@@ -312,6 +320,9 @@ {-# INLINE censor #-}  -- | Lift a @callCC@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @callCC@ discards any output from the body on entering+-- the saved continuation. liftCallCC :: (Monoid w) => CallCC m (a,w) (b,w) -> CallCC (WriterT w m) a b liftCallCC callCC f = WriterT $     callCC $ \ c ->@@ -319,6 +330,9 @@ {-# INLINE liftCallCC #-}  -- | Lift a @catchE@ operation to the new monad.+-- The uniformity property (see "Control.Monad.Signatures") implies that+-- the lifted @catchE@ discards any output from the body on entering+-- the handler. liftCatch :: Catch e m (a,w) -> Catch e (WriterT w m) a liftCatch catchE m h =     WriterT $ runWriterT m `catchE` \ e -> runWriterT (h e)

@@ -36,7 +36,7 @@  import Control.Applicative import Data.Foldable-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Monoid (Monoid(..)) import Data.Traversable (Traversable(traverse)) #endif

@@ -43,7 +43,7 @@ import qualified Control.Monad.Fail as Fail #endif import Data.Foldable-#if !(MIN_VERSION_base(4,8,0))+#if !(MIN_VERSION_base(4,8,0)) || defined(__MHS__) import Data.Traversable (Traversable(traverse)) #endif import Data.Monoid

@@ -1,5 +1,21 @@ -*-change-log-*- +0.6.3.0 Ross Paterson <R.Paterson@city.ac.uk> Jan 2026+	* Add Control.Monad.Trans.Except.onE+	* Add strictToLazyState and lazyToStrictStateT++0.6.2.0 Ross Paterson <R.Paterson@city.ac.uk> Apr 2025+	* Redefine runAccumT, runExceptT and runSelectT as fields+	* Document strictness of some transformers++0.6.1.2 Ross Paterson <R.Paterson@city.ac.uk> Sep 2024+	* Portability fixes for MicroHs+	* Include image files in the bundle+	* Expand ExceptT documentation++0.6.1.1 Ross Paterson <R.Paterson@city.ac.uk> Aug 2023+	* Additions to documentation, especially of AccumT.+ 0.6.1.0 Ross Paterson <R.Paterson@city.ac.uk> Feb 2023 	* Add instances of Foldable1 (class added to base-4.18) 	* Add modifyM to StateT transformers

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@@ -1,5 +1,5 @@ name:         transformers-version:      0.6.1.0+version:      0.6.3.0 license:      BSD3 license-file: LICENSE author:       Andy Gill, Ross Paterson@@ -31,9 +31,12 @@     the @mtl@ or @monads-tf@ packages, which automatically lift operations     introduced by monad transformers through other transformers. build-type: Simple-extra-source-files:+extra-doc-files:     changelog-cabal-version: >= 1.10+    images/bind-AccumT.svg+    images/bind-ReaderT.svg+    images/bind-WriterT.svg+cabal-version: 1.18  source-repository head   type: darcs@@ -43,13 +46,13 @@   default-language: Haskell2010   build-depends: base >= 2 && < 6   hs-source-dirs: .-  if !impl(ghc>=7.9)+  if impl(ghc<7.9)     -- Data.Functor.Identity was moved into base-4.8.0.0 (GHC 7.10)     -- see also https://ghc.haskell.org/trac/ghc/ticket/9664     -- NB: using impl(ghc>=7.9) instead of fragile Cabal flags     hs-source-dirs: legacy/pre709     exposed-modules: Data.Functor.Identity-  if !impl(ghc>=7.11)+  if impl(ghc<7.11)     -- modules moved into base-4.9.0 (GHC 8.0)     -- see https://ghc.haskell.org/trac/ghc/ticket/10773     -- see https://ghc.haskell.org/trac/ghc/ticket/11135@@ -62,7 +65,7 @@       Data.Functor.Sum   if impl(ghc>=7.2 && <7.5)     -- Prior to GHC 7.5, GHC.Generics lived in ghc-prim-    build-depends: ghc-prim+    build-depends: ghc-prim < 0.3   exposed-modules:     Control.Applicative.Backwards     Control.Applicative.Lift