In Control.Exception, there's:
> data Exception = ...
> | DynException Dynamic
> | ...
and
> throwIO :: Exception -> IO a
so, what you want is probably something like:
> if rc < 0
> then throwIO (DynException (toDyn ("Err", rc)))
> else ...
and then when you catch, use fromDyn(amic) to get the value out if you can
predict its type...
HTH.
- Hal
--
Hal Daume III | [EMAIL PROTECTED]
"Arrest this man, he talks in maths." | www.isi.edu/~hdaume
On Wed, 4 Jun 2003, Bayley, Alistair wrote:
> (I know I'm asking some noddy questions, but hey, that's what this list is
> for...)
>
> How do I create IOError exceptions? System.IO.Error has two functions that
> create IOErrors: userError and mkIOError. However, both of them take a
> String (I assume containing a description of the problem), and mkIOError
> takes optional Handle and FilePath args.
>
> http://www.haskell.org/ghc/docs/latest/html/base/System.IO.Error.html
>
> What I'd like to do is stuff some more information into the exception (a bit
> like Java exceptions), along the lines of:
>
> > mkIOError :: a -> IOError
>
> where I could choose to use it like this (ociHandleAlloc is a foreign C
> function):
>
> > handleAlloc2 handleType env ptr = do
> > rc <- ociHandleAlloc env ptr handleType 0 0
> > if rc < 0
> > then ioError (mkIOError ("Couldn't allocate handle", rc))
> > else peek ptr
>
>
> When I catch the exception (currently in main) I would like to interrogate
> it to get the values I stuffed in it (in this case a (String, Int) tuple),
> and then do some error reporting by calling another function which decodes
> the error number.
>
> Is this the wrong way to go about error handling? Or is it relatively simple
> to create your own IOErrors? Have I missed something in the docs?
>
>
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