0
我讀了真實世界哈斯克爾第9章 有一種maybeIO函數封裝了IO功能結果變成可能:如何使用haskell控件。異常處理返回一個IO(也許)
maybeIO :: IO a -> IO (Maybe a)
maybeIO act = handle(\_ -> return Nothing) (liftM Just act)
但是這個代碼不會工作在GHC 7 +,我不知道如何修改這個代碼,以便它會GHC 7工作,我試圖
import Control.Exception (bracket, handle, SomeException(..))
maybeIO :: IO a -> IO (Maybe a)
maybeIO act = handle(\(SomeException e) -> return Nothing) (liftM Just act)
,但我得到一個解析錯誤:在頂級
是的,它的工作原理,謝謝。必須將其他代碼混淆編譯器。 – 2012-02-14 19:22:06