Add mapRec and refactor receiveUsage

bluefin-internal/src/Bluefin/Internal/Examples.hs

@@ -195,21 +195,32 @@ takeRec n done k rec = evalState n $ \s -> forEach k $ \() -> do
       modify s (subtract 1)
       receive rec
 
+mapRec ::
+  (e :> es) =>
+  (a -> b) ->
+  (forall e1. Receive b e1 -> Eff (e1 :& es) ()) ->
+  Receive a e ->
+  Eff es ()
+mapRec f k rec = forEach k $ \() -> do
+  r <- receive rec
+  pure (f r)
+
 receiveUsage ::
-  (e :> es, e3 :> es) =>
+  (e :> es, e3 :> es, e2 :> es) =>
   IOE e3 ->
   Jump e ->
+  Receive Int e2 ->
   Eff es ()
 receiveUsage io done = do
-  receiveList [1 :: Int .. 5] io done $ takeRec 2 done $ \rec -> do
+  mapRec (* 11) $ takeRec 2 done $ \rec -> do
     for_ [1 :: Int .. 3] $ \_ -> do
       i <- receive rec
       effIO io (print i)
 
 receiveExample :: IO ()
 receiveExample = runEff $ \io -> do
   withJump $ \done -> do
-    receiveUsage io done
+    receiveList [1 :: Int .. 5] io done $ receiveUsage io done
 
 -- Count the number of (strictly) positives and (strictly) negatives
 -- in a list, unless we see a zero, in which case we bail with an