#5560: case and type synonym
------------------------------------------+---------------------------------
Reporter: sleepyMonad | Owner:
Type: bug | Status: closed
Priority: normal | Milestone:
Component: Compiler | Version: 7.0.2
Resolution: invalid | Keywords:
Testcase: | Blockedby:
Difficulty: | Os: Linux
Blocking: | Architecture: x86
Failure: Incorrect result at runtime |
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Changes (by igloo):
* status: new => closed
* resolution: => invalid
Comment:
Pattern matching doesn't work like that I'm afraid. If you use the `-Wall`
flag then you will get some extra warnings like
{{{
q.hs:12:16:
Warning: This binding for `kp' shadows the existing binding
defined at q.hs:7:1
q.hs:12:16: Warning: Defined but not used: `kp'
}}}
Your definition of `switchOnEvent2` is equivalent to
{{{
switchOnEvent2 :: MyEventType -> IO ()
switchOnEvent2 x = do putStrLn "KP"
switchOnEvent2 y = do putStrLn "BP"
switchOnEvent2 _ = do putStrLn "??"
}}}
You may want something like
{{{
switchOnEvent2 :: MyEventType -> IO ()
switchOnEvent2 e
| e == kp = do putStrLn "KP"
| e == bp = do putStrLn "BP"
| otherwise = do putStrLn "??"
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/5560#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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