Example async-exception-safe retry function

Main.hs

{-# LANGUAGE BlockArguments      #-}
{-# LANGUAGE ScopedTypeVariables #-}

module Main where

import Control.Concurrent (threadDelay)
import Control.Exception

retry :: Int -> IO a -> IO a
retry n io
    | n <= 0    = io
    | otherwise = io `catch` \(_ :: SomeException) -> do
        mask \restore -> do
            restore (threadDelay 1000000)
                `onException` restore (retry (n - 1) io)

            restore (retry (n - 1) io)

main :: IO ()
main = do
    retry 4 (print 1)
    retry 4 (fail "Urk!")