Add Receive synonym, receive and feedEach

bluefin-internal/src/Bluefin/Internal.hs

@@ -138,7 +138,7 @@ connectCoroutines m1 m2 = unsafeProvideIO $ \io -> do
   race (useImplWithin t1) (useImplWithin t2) io
 
 receiveStream ::
-  (forall e. Coroutine () a e -> Eff (e :& es) r) ->
+  (forall e. Receive a e -> Eff (e :& es) r) ->
   (forall e. Stream a e -> Eff (e :& es) r) ->
   Eff es r
 receiveStream r s = connectCoroutines r (\() -> s)
@@ -271,6 +271,8 @@ newtype Coroutine a b (e :: Effects) = MkCoroutine (a -> Eff e b)
 -- @a@ and then expects values of type @()@.
 type Stream a = Coroutine a ()
 
+type Receive a = Coroutine () a
+
 -- | You can define a @Handle@ instance for your compound handles.  As
 -- an example, an "application" handle with a dynamic effect for
 -- database queries, a concrete effect for application state and a
@@ -722,6 +724,22 @@ enumerateFrom n ss st =
     yield st (ii, s)
     put i (ii + 1)
 
+-- | A version of 'forEach' specialized to @Receive@.  Every time the
+-- @Receive@ attempts to @receive@ a @b@, feed it the one created by
+-- the handler.
+feedEach ::
+  ( forall e.
+    Receive b e ->
+    Eff (e :& es) r
+  ) ->
+  -- | Value to send to each @receive@ in the body.
+  Eff es b ->
+  Eff es r
+feedEach k e = forEach k (\() -> e)
+
+receive :: (e :> es) => Receive a e -> Eff es a
+receive r = yieldCoroutine r ()
+
 type EarlyReturn = Exception
 
 -- | Run an 'Eff' action with the ability to return early to this