I have a question about the streaming package.

I want to putStrLn each element and then print the length of str, so I could do this:

import Streaming

import qualified Streaming.Prelude as SP

doit :: Stream (Of String) IO () -> IO ()

doit str =

  do

    SP.mapM_ putStrLn str

    SP.length_ str >>= print

However, will this result in doing 2 passes over str so that the memory requirement is not constant? If so, is there a simple way to combine the two actions so that only pass is needed? I could probably use a counter in a StateT but that's not really simple. More generally, are there techniques for combining folds like how one would with the foldl package?