setInterval.hs

-- ghc --make -O2 -threaded setInterval.hs
import Control.Concurrent
import Control.Exception


setInterval action microsecs = do
    mvar <- newEmptyMVar
    setInterval' mvar action microsecs
    takeMVar mvar

setInterval' mvar action microsecs = do
    threadId <- forkIO (loop `finally` putMVar mvar ())
    return threadId
  where
    loop = do
        threadDelay microsecs
        action
        loop

main = do
    setInterval (do
        putStrLn "yolo"
        ) 1000000