如何在帶有符號的列表上使用映射 - 即避免使用類型“[IO()]”鍵入`IO()'? [英]How do I use map over a list with do notation - ie avoid type `IO ()' with type `[IO ()]'?
如何在`unsafePerformIO`中強制評估IO操作? [英]How do I force evaluation of an IO action within `unsafePerformIO`?