On Mon, 2008-11-03 at 09:26 -0800, Sigbjorn Finne wrote:
> On 11/3/2008 07:34, Jason Dagit wrote:
> > ....
> >
> > Ah, but I had one more question that I don't think anyone has answered
> > yet. That is, how to deal with multiple types of exceptions.
> > Suppose, as a concrete example, that I was looking out for both
> > ExitCode and PatternMatchFail exceptions. Maybe I'm being naive, but
> > it seems like I'm in that situation again where I have to catch all
> > and then check if fromException succeeds on either PatternMatchFile or
> > ExitCode types. And then throw if it both give Nothing?
> >
> >
> One way to do this now is to use Control.Exception.catches:
>
> catches :: IO a -> [Handler a] -> IO a
> data Handler a where
> Handler :: forall a e. (Exception e) => (e -> IO a) -> Handler a
ie:
action
`catches`
[ \(e :: ExitCode) -> ...
, \(e :: PatternMatchFail) -> ...
]
or just by using multiple catch clauses:
action
`catch` (\(e :: ExitCode) -> ...)
`catch` (\(e :: PatternMatchFail) -> ...)
Duncan
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