消费者

Created: November-22, 2018

Consumer 只能从上游获得值。

 placeholderCopytype Consumer a = Proxy () a () X
await::Monad m => Consumer a m a

例如：

 placeholderCopyfancyPrint::MonadIO m => Consumer String m ()
fancyPrint = forever $ do
  numStr <- await
  liftIO $ putStrLn ("I received: " ++ numStr)