[Haskell-cafe] Stream processing

[oleg at okmij.org]

I'm a bit curious
  > * be reliable in the presence of async exceptions (solved by conduit,
  >   pipes-safe),
  >
  > * hold on to resources only as long as necessary (solved by conduit
  >   and to some degree by pipes-safe),

Are you aware of
        http://okmij.org/ftp/Streams.html#regions
which describes both resource deallocation and async signals. Could
you tell what you think is deficient in that code?

  > * ideally also allow upstream communication (solved by pipes and to
  >   some degree by conduit).

Are you aware (of, admittedly) old message whose title was specifically
  ``Sending messages up-and-down the iteratee-enumerator chain''
http://www.haskell.org/pipermail/haskell-cafe/2011-May/091870.html
(there were several messages in that thread). Here is the code for
those messages
        http://okmij.org/ftp/Haskell/Iteratee/UpDown.hs