Changes between Version 1 and Version 2 of monad-coroutine

Timestamp:

03/20/10 20:24:32 (3 years ago)

Author:

blamario (IP: 99.241.117.248)

Comment:

--

monad-coroutine

@@ -2 +2 @@
 = Package monad-coroutine =
 
-This library, implemented by the Control.Monad.Coroutine module, provides a limited coroutine functionality in Haskell. The centerpiece of the approach is the monad transformer Coroutine, that transforms an arbitrary monadic computation into a suspendable and resumable one. The basic definition is simple:
+This library, implemented by the `Control.Monad.Coroutine` module, provides a limited coroutine functionality in Haskell. The centerpiece of the approach is the monad transformer `Coroutine`, which transforms an arbitrary monadic computation into a suspendable and resumable one. The basic definition is simple:
 
 {{{
-newtype Coroutine s m r = Coroutine {resume :: m (CoroutineState s m r)}
-
-data CoroutineState s m r = Done r | Suspend! (s (Coroutine s m r))
+newtype Coroutine s m r = Coroutine {resume :: m (Either (s (Coroutine s m r)) r)}
 
 instance (Functor s, Monad m) => Monad (Coroutine s m) where
-   return x = Coroutine (return (Done x))
-   t >>= f = Coroutine (resume t >>= apply f)
-      where apply f (Done x) = resume (f x)
-            apply f (Suspend s) = return (Suspend (fmap (>>= f) s))
+   return = Coroutine . return . Right
+   t >>= f = Coroutine (resume t >>= either (return . Left . fmap (>>= f)) (resume . f))
 }}}
 
-The Coroutine transformer type is parameterized by a functor. Here is an example of one functor particularly useful for a Coroutine computation:
+The Coroutine transformer type is parameterized by a functor. The functor in question wraps the resumption of a suspended coroutine, and it can carry other information as well. Module `Control.Monad.Coroutine.SuspensionFunctors` exports some useful functors, one of which is `Yield`:
 
 {{{