[Haskell-beginners] First steps with Streaming library

[aquagnu]

I'm trying to start working with Streaming package. First attempt
is to simulate source of stream items (I call the function "gen")
and some processor ("proc"). Both should be stateful: to be able
to sabe some info about processing steps, etc.

  ...
  import Streaming
  import qualified Streaming.Prelude as S
  ...

  gen :: S.Stream (S.Of Int) IO [String]
  gen = do
    S.yield 1000
    S.yield 2000
    x <- lift getLine
    return ["a", "b", "c", x] -- results

  proc :: S.Stream (S.Of Int) IO [String] -> S.Stream (S.Of Int) IO [String]
  proc str = do
    e <- str
    lift $ print "Enter x:"
    x <- lift getLine
    return $ e ++ [" -- " ++ x] -- put stream items in result
  
  main :: IO
  main = do
    s <- S.mapM_ print $ S.map show gen
    p <- S.mapM_ print $ proc gen
    putStr "s: " >> print s
    putStr "p: " >> print p

And I try to simulate "piping" between "gen" and "proc", seems that
function application is enought to compose producers and consumers. But
this snippet is not correct: "e <- str" extracts element not from
stream, but from results (of "gen"). Even more, I don't know how to
"yield" new items, based on stream items. Something like "await" of
Conduit, or like in Python "for e in str: ... yield modified(e)...". Is
it possible to do it with "do" notation?

---
Best,
  Paul