Haskell - loop over user input

Question

I have a program in haskell that has to read arbitrary lines of input from the user and when the user is finished the accumulated input has to be sent to a function.

In

Answer 1

Using pipes-4.0, which is coming out this weekend:

import Pipes
import qualified Pipes.Prelude as P

f :: [String] -> IO ()
f = ??

main = do
    contents <- P.toListM (P.stdinLn >-> P.takeWhile (/= "q"))
    f contents

That loads all the lines into memory. However, you can also process each line as it is being generated, too:

f :: String -> IO ()

main = runEffect $
    for (P.stdinLn >-> P.takeWhile (/= "q")) $ \str -> do
        lift (f str)

That will stream the input and never load more than one line into memory.