blob: 253d44dfc8ecd0cb36e0abf9eefee515597c3508 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
|
module Main where
import Control.Concurrent
-- simple handshaking using two MVars,
-- must context switch twice for each character.
main = do
ready <- newEmptyMVar
datum <- newEmptyMVar
let
reader = do
putMVar ready ()
char <- takeMVar datum
if (char == '\n')
then return ()
else do putChar char; reader
writer "" = do
takeMVar ready
putMVar datum '\n'
writer (c:cs) = do
takeMVar ready
putMVar datum c
writer cs
forkIO reader
writer "Hello World"
|
