bracket.hs

-- Modified from https://www.snoyman.com/blog/2018/10/raii-better-than-bracket-pattern

import Control.Exception (bracket)
import Text.Printf (printf)

data MyResource = MyResource { handle :: Int }

newMyResource :: IO MyResource
newMyResource = do
  putStrLn "Creating a new MyResource"
  pure MyResource { handle = 0 }

closeMyResource :: MyResource -> IO ()
closeMyResource resource = printf "Closing MyResource @ %d\n" (handle resource)

withMyResource :: (MyResource -> IO a) -> IO a
withMyResource = bracket newMyResource closeMyResource

useMyResource :: MyResource -> IO ()
useMyResource resource = printf "Using MyResource @ %d\n" (handle resource)

main :: IO ()
main = do
  -- withMyResource useMyResource
  myResource <- withMyResource pure
  useMyResource myResource