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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 | -- Hoogle documentation, generated by Haddock
-- See Hoogle, http://www.haskell.org/hoogle/
-- | Lift control operations, like exception catching, through monad transformers
--
-- This package defines the type class <tt>MonadBaseControl</tt>, a
-- subset of <tt>MonadBase</tt> into which generic control operations
-- such as <tt>catch</tt> can be lifted from <tt>IO</tt> or any other
-- base monad. Instances are based on monad transformers in
-- <tt>MonadTransControl</tt>, which includes all standard monad
-- transformers in the <tt>transformers</tt> library except
-- <tt>ContT</tt>.
--
-- See the <tt>lifted-base</tt> package which uses <tt>monad-control</tt>
-- to lift <tt>IO</tt> operations from the <tt>base</tt> library (like
-- <tt>catch</tt> or <tt>bracket</tt>) into any monad that is an instance
-- of <tt>MonadBase</tt> or <tt>MonadBaseControl</tt>.
--
-- Note that this package is a rewrite of Anders Kaseorg's
-- <tt>monad-peel</tt> library. The main difference is that this package
-- provides CPS style operators and exploits the <tt>RankNTypes</tt> and
-- <tt>TypeFamilies</tt> language extensions to simplify and speedup most
-- definitions.
@package monad-control
@version 1.0.1.0
module Control.Monad.Trans.Control
class MonadTrans t => MonadTransControl t where type StT t a :: * where {
type family StT t a :: *;
}
-- | <tt>liftWith</tt> is similar to <tt>lift</tt> in that it lifts a
-- computation from the argument monad to the constructed monad.
--
-- Instances should satisfy similar laws as the <a>MonadTrans</a> laws:
--
-- <pre>
-- liftWith . const . return = return
-- </pre>
--
-- <pre>
-- liftWith (const (m >>= f)) = liftWith (const m) >>= liftWith . const . f
-- </pre>
--
-- The difference with <tt>lift</tt> is that before lifting the
-- <tt>m</tt> computation <tt>liftWith</tt> captures the state of
-- <tt>t</tt>. It then provides the <tt>m</tt> computation with a
-- <a>Run</a> function that allows running <tt>t n</tt> computations in
-- <tt>n</tt> (for all <tt>n</tt>) on the captured state.
liftWith :: (MonadTransControl t, Monad m) => (Run t -> m a) -> t m a
-- | Construct a <tt>t</tt> computation from the monadic state of
-- <tt>t</tt> that is returned from a <a>Run</a> function.
--
-- Instances should satisfy:
--
-- <pre>
-- liftWith (\run -> run t) >>= restoreT . return = t
-- </pre>
restoreT :: (MonadTransControl t, Monad m) => m (StT t a) -> t m a
-- | A function that runs a transformed monad <tt>t n</tt> on the monadic
-- state that was captured by <a>liftWith</a>
--
-- A <tt>Run t</tt> function yields a computation in <tt>n</tt> that
-- returns the monadic state of <tt>t</tt>. This state can later be used
-- to restore a <tt>t</tt> computation using <a>restoreT</a>.
type Run t = forall n b. Monad n => t n b -> n (StT t b)
-- | A function like <a>Run</a> that runs a monad transformer <tt>t</tt>
-- which wraps the monad transformer <tt>t'</tt>. This is used in
-- <a>defaultLiftWith</a>.
type RunDefault t t' = forall n b. Monad n => t n b -> n (StT t' b)
-- | Default definition for the <a>liftWith</a> method.
defaultLiftWith :: (Monad m, MonadTransControl n) => (forall b. n m b -> t m b) -> (forall o b. t o b -> n o b) -> (RunDefault t n -> m a) -> t m a
-- | Default definition for the <a>restoreT</a> method.
defaultRestoreT :: (Monad m, MonadTransControl n) => (n m a -> t m a) -> m (StT n a) -> t m a
class MonadBase b m => MonadBaseControl b m | m -> b where type StM m a :: * where {
type family StM m a :: *;
}
-- | <tt>liftBaseWith</tt> is similar to <tt>liftIO</tt> and
-- <tt>liftBase</tt> in that it lifts a base computation to the
-- constructed monad.
--
-- Instances should satisfy similar laws as the <tt>MonadIO</tt> and
-- <a>MonadBase</a> laws:
--
-- <pre>
-- liftBaseWith . const . return = return
-- </pre>
--
-- <pre>
-- liftBaseWith (const (m >>= f)) = liftBaseWith (const m) >>= liftBaseWith . const . f
-- </pre>
--
-- The difference with <tt>liftBase</tt> is that before lifting the base
-- computation <tt>liftBaseWith</tt> captures the state of <tt>m</tt>. It
-- then provides the base computation with a <a>RunInBase</a> function
-- that allows running <tt>m</tt> computations in the base monad on the
-- captured state.
liftBaseWith :: MonadBaseControl b m => (RunInBase m b -> b a) -> m a
-- | Construct a <tt>m</tt> computation from the monadic state of
-- <tt>m</tt> that is returned from a <a>RunInBase</a> function.
--
-- Instances should satisfy:
--
-- <pre>
-- liftBaseWith (\runInBase -> runInBase m) >>= restoreM = m
-- </pre>
restoreM :: MonadBaseControl b m => StM m a -> m a
-- | A function that runs a <tt>m</tt> computation on the monadic state
-- that was captured by <a>liftBaseWith</a>
--
-- A <tt>RunInBase m</tt> function yields a computation in the base monad
-- of <tt>m</tt> that returns the monadic state of <tt>m</tt>. This state
-- can later be used to restore the <tt>m</tt> computation using
-- <a>restoreM</a>.
type RunInBase m b = forall a. m a -> b (StM m a)
-- | Handy type synonym that composes the monadic states of <tt>t</tt> and
-- <tt>m</tt>.
--
-- It can be used to define the <a>StM</a> for new
-- <a>MonadBaseControl</a> instances.
type ComposeSt t m a = StM m (StT t a)
-- | A function like <a>RunInBase</a> that runs a monad transformer
-- <tt>t</tt> in its base monad <tt>b</tt>. It is used in
-- <a>defaultLiftBaseWith</a>.
type RunInBaseDefault t m b = forall a. t m a -> b (ComposeSt t m a)
-- | Default defintion for the <a>liftBaseWith</a> method.
--
-- Note that it composes a <a>liftWith</a> of <tt>t</tt> with a
-- <a>liftBaseWith</a> of <tt>m</tt> to give a <a>liftBaseWith</a> of
-- <tt>t m</tt>:
--
-- <pre>
-- defaultLiftBaseWith = \f -> <a>liftWith</a> $ \run ->
-- <a>liftBaseWith</a> $ \runInBase ->
-- f $ runInBase . run
-- </pre>
defaultLiftBaseWith :: (MonadTransControl t, MonadBaseControl b m) => (RunInBaseDefault t m b -> b a) -> t m a
-- | Default definition for the <a>restoreM</a> method.
--
-- Note that: <tt>defaultRestoreM = <a>restoreT</a> .
-- <a>restoreM</a></tt>
defaultRestoreM :: (MonadTransControl t, MonadBaseControl b m) => ComposeSt t m a -> t m a
-- | An often used composition: <tt>control f = <a>liftBaseWith</a> f
-- >>= <a>restoreM</a></tt>
control :: MonadBaseControl b m => (RunInBase m b -> b (StM m a)) -> m a
-- | Embed a transformer function as an function in the base monad
-- returning a mutated transformer state.
embed :: MonadBaseControl b m => (a -> m c) -> m (a -> b (StM m c))
-- | Performs the same function as <a>embed</a>, but discards transformer
-- state from the embedded function.
embed_ :: MonadBaseControl b m => (a -> m ()) -> m (a -> b ())
-- | Capture the current state of a transformer
captureT :: (MonadTransControl t, Monad (t m), Monad m) => t m (StT t ())
-- | Capture the current state above the base monad
captureM :: MonadBaseControl b m => m (StM m ())
-- | <tt>liftBaseOp</tt> is a particular application of <a>liftBaseWith</a>
-- that allows lifting control operations of type:
--
-- <tt>((a -> b c) -> b c)</tt> to: <tt>(<a>MonadBaseControl</a> b
-- m => (a -> m c) -> m c)</tt>.
--
-- For example:
--
-- <pre>
-- liftBaseOp alloca :: <a>MonadBaseControl</a> <a>IO</a> m => (Ptr a -> m c) -> m c
-- </pre>
liftBaseOp :: MonadBaseControl b m => ((a -> b (StM m c)) -> b (StM m d)) -> ((a -> m c) -> m d)
-- | <tt>liftBaseOp_</tt> is a particular application of
-- <a>liftBaseWith</a> that allows lifting control operations of type:
--
-- <tt>(b a -> b a)</tt> to: <tt>(<a>MonadBaseControl</a> b m => m
-- a -> m a)</tt>.
--
-- For example:
--
-- <pre>
-- liftBaseOp_ mask_ :: <a>MonadBaseControl</a> <a>IO</a> m => m a -> m a
-- </pre>
liftBaseOp_ :: MonadBaseControl b m => (b (StM m a) -> b (StM m c)) -> (m a -> m c)
-- | <tt>liftBaseDiscard</tt> is a particular application of
-- <a>liftBaseWith</a> that allows lifting control operations of type:
--
-- <tt>(b () -> b a)</tt> to: <tt>(<a>MonadBaseControl</a> b m => m
-- () -> m a)</tt>.
--
-- Note that, while the argument computation <tt>m ()</tt> has access to
-- the captured state, all its side-effects in <tt>m</tt> are discarded.
-- It is run only for its side-effects in the base monad <tt>b</tt>.
--
-- For example:
--
-- <pre>
-- liftBaseDiscard forkIO :: <a>MonadBaseControl</a> <a>IO</a> m => m () -> m ThreadId
-- </pre>
liftBaseDiscard :: MonadBaseControl b m => (b () -> b a) -> (m () -> m a)
-- | <tt>liftBaseOpDiscard</tt> is a particular application of
-- <a>liftBaseWith</a> that allows lifting control operations of type:
--
-- <tt>((a -> b ()) -> b c)</tt> to: <tt>(<a>MonadBaseControl</a> b
-- m => (a -> m ()) -> m c)</tt>.
--
-- Note that, while the argument computation <tt>m ()</tt> has access to
-- the captured state, all its side-effects in <tt>m</tt> are discarded.
-- It is run only for its side-effects in the base monad <tt>b</tt>.
--
-- For example:
--
-- <pre>
-- liftBaseDiscard (runServer addr port) :: <a>MonadBaseControl</a> <a>IO</a> m => m () -> m ()
-- </pre>
liftBaseOpDiscard :: MonadBaseControl b m => ((a -> b ()) -> b c) -> (a -> m ()) -> m c
-- | Transform an action in <tt>t m</tt> using a transformer that operates
-- on the underlying monad <tt>m</tt>
liftThrough :: (MonadTransControl t, Monad (t m), Monad m) => (m (StT t a) -> m (StT t b)) -> t m a -> t m b
instance Control.Monad.Trans.Control.MonadTransControl Control.Monad.Trans.Identity.IdentityT
instance Control.Monad.Trans.Control.MonadTransControl Control.Monad.Trans.Maybe.MaybeT
instance Control.Monad.Trans.Error.Error e => Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.Error.ErrorT e)
instance Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.Except.ExceptT e)
instance Control.Monad.Trans.Control.MonadTransControl Control.Monad.Trans.List.ListT
instance Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.Reader.ReaderT r)
instance Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.State.Lazy.StateT s)
instance Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.State.Strict.StateT s)
instance GHC.Base.Monoid w => Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.Writer.Lazy.WriterT w)
instance GHC.Base.Monoid w => Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.Writer.Strict.WriterT w)
instance GHC.Base.Monoid w => Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.RWS.Lazy.RWST r w s)
instance GHC.Base.Monoid w => Control.Monad.Trans.Control.MonadTransControl (Control.Monad.Trans.RWS.Strict.RWST r w s)
instance Control.Monad.Trans.Control.MonadBaseControl GHC.Types.IO GHC.Types.IO
instance Control.Monad.Trans.Control.MonadBaseControl GHC.Base.Maybe GHC.Base.Maybe
instance Control.Monad.Trans.Control.MonadBaseControl (Data.Either.Either e) (Data.Either.Either e)
instance Control.Monad.Trans.Control.MonadBaseControl [] []
instance Control.Monad.Trans.Control.MonadBaseControl ((->) r) ((->) r)
instance Control.Monad.Trans.Control.MonadBaseControl Data.Functor.Identity.Identity Data.Functor.Identity.Identity
instance Control.Monad.Trans.Control.MonadBaseControl GHC.Conc.Sync.STM GHC.Conc.Sync.STM
instance Control.Monad.Trans.Control.MonadBaseControl (GHC.ST.ST s) (GHC.ST.ST s)
instance Control.Monad.Trans.Control.MonadBaseControl (Control.Monad.ST.Lazy.Imp.ST s) (Control.Monad.ST.Lazy.Imp.ST s)
instance Control.Monad.Trans.Control.MonadBaseControl b m => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.Identity.IdentityT m)
instance Control.Monad.Trans.Control.MonadBaseControl b m => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.Maybe.MaybeT m)
instance Control.Monad.Trans.Control.MonadBaseControl b m => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.List.ListT m)
instance Control.Monad.Trans.Control.MonadBaseControl b m => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.Reader.ReaderT r m)
instance Control.Monad.Trans.Control.MonadBaseControl b m => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.State.Strict.StateT s m)
instance Control.Monad.Trans.Control.MonadBaseControl b m => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.State.Lazy.StateT s m)
instance Control.Monad.Trans.Control.MonadBaseControl b m => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.Except.ExceptT e m)
instance (Control.Monad.Trans.Error.Error e, Control.Monad.Trans.Control.MonadBaseControl b m) => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.Error.ErrorT e m)
instance (GHC.Base.Monoid w, Control.Monad.Trans.Control.MonadBaseControl b m) => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.Writer.Strict.WriterT w m)
instance (GHC.Base.Monoid w, Control.Monad.Trans.Control.MonadBaseControl b m) => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.Writer.Lazy.WriterT w m)
instance (GHC.Base.Monoid w, Control.Monad.Trans.Control.MonadBaseControl b m) => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.RWS.Strict.RWST r w s m)
instance (GHC.Base.Monoid w, Control.Monad.Trans.Control.MonadBaseControl b m) => Control.Monad.Trans.Control.MonadBaseControl b (Control.Monad.Trans.RWS.Lazy.RWST r w s m)
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