haskell の Data.IORef
IO モナド中で更新できる値を扱う.
main = do ior <- newIORef 0 writeIORef ior 5 v <- readIORef ior print v -- => 5 modifyIORef ior (+ 1) v <- readIORef ior print v -- => 6
IO モナド中で更新できる値を扱う.
main = do ior <- newIORef 0 writeIORef ior 5 v <- readIORef ior print v -- => 5 modifyIORef ior (+ 1) v <- readIORef ior print v -- => 6