Initial commit

src/Devel/Main.hs

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+module Devel.Main where
+
+import Main (defaultMain)
+import Control.Concurrent
+import Control.Monad (void)
+import Data.IORef (IORef, newIORef, readIORef, writeIORef)
+import Foreign.Store (Store(..), lookupStore, readStore, storeAction, withStore)
+import GHC.Word (Word32)
+
+update :: IO ()
+update = do
+  lookupStore tidStoreNum >>= maybe setupNew restart
+  where
+    doneStore :: Store (MVar ())
+    doneStore = Store 0
+    setupNew :: IO ()
+    setupNew = do
+      done <- storeAction doneStore newEmptyMVar
+      tid <- start done
+      void $ storeAction (Store tidStoreNum) (newIORef tid)
+    restart tidStore = modifyStoredIORef tidStore $ \tid -> do
+      killThread tid
+      withStore doneStore takeMVar
+      readStore doneStore >>= start
+    start :: MVar () -> IO ThreadId
+    start done = forkFinally defaultMain (\_ -> putMVar done ())
+
+modifyStoredIORef :: Store (IORef a) -> (a -> IO a) -> IO ()
+modifyStoredIORef store f = withStore store $ \ref -> do
+  v <- readIORef ref
+  f v >>= writeIORef ref
+
+tidStoreNum :: Word32
+tidStoreNum = 1

src/Main.hs

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+module Main where
+
+defaultMain :: IO ()
+defaultMain = putStrLn "Hello haskell"
+
+main :: IO ()
+main = defaultMain