Hi Chul-Woong,

Deepseq package can be used to make sure a list is actually fully constructed before it's used.

import System.IO
import Control.DeepSeq

main :: IO ()
main = do

    s <- getContents
    s `deepseq` hClose stdin
    putStrLn "ECHO result"
    putStr s

Cheers

2014-07-24 9:07 GMT+03:00 양철웅 <cwyang@aranetworks.com>:

Hi, all.

Haskell's lazy IO causes below program to 

write back "ECHO result" to the user 

even if he doesn't give any input to the program.

test1 :: IO ()

test1 = do

  l <- fmap lines getContents

  putStrLn "ECHO result"

  putStr $ unlines l

If the client logic, that is the part for feeding data to this program

and wait for the response, expect the server logic to respond

only after all the client's request data are feed to the server logic,

the behaviour could be problematic.

I'm now writing simple web server, as you might guess, and

my web server responds "HTTP/1.1" before any client's request

are given. I'm using hGetContents and web server's logic is

basically same with above code skeleton.

How can I tell the program to respond data only after all the

requests are feed? Any directions are welcomed.

Thanks.

Chul-Woong

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