Is there a quick-starting Haskell interpreter suitable for scripting?

Question

Does anyone know of a quick-starting Haskell interpreter that would be suitable for use in writing shell scripts? Running \'hello world\' using Hugs took 400ms on my old laptop

Answer 1

What about having a ghci daemon and a feeder script that takes the script path and location, communicates with the already running ghci process to load and execute the script in the proper directory and pipes the output back to the feeder script for stdout?

Unfortunately, I have no idea how to write something like this, but it seems like it could be really fast judging by the speed of :l in ghci. As it seems most of the cost in runhaskell is in starting up ghci, not parsing and running the script.

Edit: After some playing around, I found the Hint package (a wrapper around the GHC API) to be of perfect use here. The following code will load the passed in module name (here assumed to be in the same directory) and will execute the main function. Now 'all' that's left is to make it a daemon, and have it accept scripts on a pipe or socket.

import Language.Haskell.Interpreter
import Control.Monad

run = runInterpreter . test

test :: String -> Interpreter ()
test mname = 
  do
    loadModules [mname ++ ".hs"]
    setTopLevelModules [mname]
    res <- interpret "main" (as :: IO())
    liftIO res

Edit2: As far as stdout/err/in go, using this specific GHC trick It looks like it would be possible to redirect the std's of the client program into the feeder program, then into some named pipes (perhaps) that the daemon is connected to at all times, and then have the daemon's stdout back to another named pipe that the feeder program is listening to. Pseudo-example:

grep ... | feeder my_script.hs | xargs ...
            |   ^---------------- <
            V                      |
         named pipe -> daemon -> named pipe

Here the feeder would be a small compiled harness program to just redirect the std's into and then back out of the daemon and give the name and location of the script to the daemon.