mconcat package:streaming

mconcat :: (Monad m, Monoid w) => Stream (Of w) m r -> m (Of w r)
streaming Streaming.Prelude
Fold streamed items into their monoidal sum 
>>> S.mconcat $ S.take 2 $ S.map (Data.Monoid.Last . Just) S.stdinLn
first<Enter>
last<Enter>
Last {getLast = Just "last"} :> ()
mconcat_ :: (Monad m, Monoid w) => Stream (Of w) m r -> m w
streaming Streaming.Prelude