Add 'resource' combinator

Sometimes its necessary to lift pure values into the `Resource` monad
within the `RequestT` monad transformer, e.g. in `whenDone` actions.

Sound/SC3/Server/Monad/Request.hs

@@ -21,6 +21,7 @@ module Sound.SC3.Server.Monad.Request
   , AllocT
   -- * Resources
   , Resource
+  , resource
   , extract
   , after
   , after_
@@ -156,6 +157,10 @@ newtype Resource m a = Resource { extract :: ServerT m a -- ^ Extract result fro
                                 }
                        deriving (Applicative, Functor, Monad)
 
+-- | Return a pure value as a 'Resource' in the 'RequestT' monad transformer.
+resource :: Monad m => a -> RequestT m (Resource m a)
+resource = return . return
+
 -- | Register a cleanup action that is executed after the notification has been
 -- received and return the deferred notification result.
 after :: MonadIO m => Notification a -> AllocT m () -> RequestT m (Resource m a)

examples/hello.hs

@@ -5,7 +5,7 @@ import           Sound.SC3.Server.Monad.Command
 -- You need the hsc3-server-internal package in order to use the internal server
 --import           Sound.SC3.Server.Monad.Process.Internal (withDefaultInternal)
 import           Sound.SC3.Server.Monad.Process (withDefaultSynth)
-import           Sound.SC3.Server.Monad.Request ((!>), async, extract, whenDone)
+import           Sound.SC3.Server.Monad.Request ((!>), async, extract, resource, whenDone)
 import           Sound.SC3.Server.Notification
 import           Sound.OpenSoundControl (immediately)
 import qualified Sound.OpenSoundControl as OSC
@@ -33,7 +33,7 @@ main = run $ do
     r <- rootNode
     synth <- extract =<< immediately !> do
         d_recv "hsc3-server:sine" sine `whenDone`
-            \sd -> s_new sd AddToTail r [("freq", 440), ("amp", 0.2)]
+            \sd -> resource =<< s_new sd AddToTail r [("freq", 440), ("amp", 0.2)]
     fork statusLoop
     pauseThread 10
     immediately !> s_release 0 synth