Run a process (drip launching clojure here for example) using Frege

ProcessTest.fr

module hellofrege.ProcessTest where

data ProcessBuilder = mutable native java.lang.ProcessBuilder where
    native new :: MutableIO StringArr -> IO ProcessBuilder
    native redirectErrorStream :: ProcessBuilder -> Bool -> IO ()
    native start :: ProcessBuilder -> IO Process throws IOException
    native directory :: ProcessBuilder -> MutableIO File -> IO ProcessBuilder
    
data Process = mutable native java.lang.Process where
    native getOutputStream :: Process -> IO OutputStream
    native getInputStream :: Process -> IO InputStream
    
fromListST :: [String] -> STMutable u StringArr
fromListST strings = (StringArr.new strings.length >>= loop 0 strings) where
    loop j (x:xs) arr = do StringArr.setAt arr j x; loop (j+1) xs arr
    loop j []     arr = return arr
fromList strings = ST.run (fromListST strings >>= readonly id) 

getOut :: InputStream -> IO [String]
getOut ins = do
    isr <- InputStreamReader.new ins "utf-8"
    br <- BufferedReader.new isr
    br.getLines
    
main _ = do
    let cmd = ["drip", "-jar", "clojure-1.5.1.jar", "-e", "(+ 1 2 3)"] 
    pb <- fromListST cmd >>= ProcessBuilder.new
    dir <- File.new "bin/clojure-1.5.1"
    pb.directory dir
    pb.redirectErrorStream true
    process <- pb.start
    pout <- process.getInputStream
    output <- getOut pout 
    mapM_ println output
  `catch` ioe where
  	ioe :: IOException -> IO ()
  	ioe e = println e.getMessage