我正在开发一个TCP客户端,该客户端从流中获取指定种类的消息,并且发现我自己使用了大量的除非表达式和表达式。例如:
hunt :: Socket -> ThreadId -> IO ()
hunt conn t = do threadDelay 1000000
msg <- recv conn 1024
unless (C.isInfixOf "1b14010102" $ encode msg) $ hunt conn t
when (C.isInfixOf "1b14010102" $ encode msg) $ do
threadDelay 7000000
sendAll conn $ goHunt
msg <- recv conn 1024
threadDelay 3000000
close conn
killThread t
我试图建立一个像这样的助手:
waitfor :: ByteString -> Socket -> t -> (ByteString -> Socket -> t -> IO ()) -> IO ()
waitfor str conn tid f = do
threadDelay 1000000
msg <- recv conn 1024
let m = C.isInfixOf str msg
unless m $ waitfor str conn tid f
when m $ f msg conn tid
然后,我可以重新使用助手:
main = do
...
tid <- myThreadId
conn <- joinWorld u
waitfor "1b14010102" conn tid hunt.
但是,如果我还有另一个功能(与
hunt
不同,它需要3个参数)hunt' :: ByteString -> Socket -> ThreadId -> IO ()
hunt' idx conn t = do threadDelay 1000000
msg <- recv conn 1024
unless (C.isInfixOf "0300aa0801" $ encode msg) $ hunt' conn t
when (C.isInfixOf "0300aa0801" $ encode msg) $ do
threadDelay 1000000
sendAll conn $ goHunt' idx
threadDelay 3000000
close conn
killThread t
那么我就不能使用
waitfor
,而需要再次使用when
/ unless
。那么,Haskell是否具有when
/ unless
的组合?如果没有,那么对于我的情况有什么更好的方法? 最佳答案
您可以使用if ... then ... else
。
例如,
waitfor :: ByteString -> Socket -> t -> (ByteString -> Socket -> t -> IO ()) -> IO ()
waitfor str conn tid f = do
threadDelay 1000000
msg <- recv conn 1024
if C.isInfixOf str msg
then waitfor str conn tid f
else f msg conn tid