Re: Control.Exception

I think the best way to get backwards compatibility is to flesh out and use the extensible-exceptions package that Ian started, which models extensible exceptions on top of the old exception mechanism. Alternatively, you can decide not to use extensible exceptions and have your package depend on base-3 instead of base-4. For a library, however, I don't think there's a good solution, since most of the time changing the exception mechanism for the library will make the library incompatible with existing clients. I guess the best way to deal with this is to properly use the package versioning policy and hope that clients specify their dependencies precisely. 2008/11/2 Sigbjorn Finne :

(+1) to that request - what is the "best practices" for portable exception handling code that straddles version 6.10, i.e. that compiles with compilers at either side with minimal fuss? I can imagine a couple of alternatives, but would like to hear what others are doing here.

thanks --sigbjorn "likes backward code compatibility"

On 11/1/2008 18:15, Jason Dagit wrote:

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On Wed, Oct 8, 2008 at 1:19 AM, Simon Marlow wrote:

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Johannes Waldmann wrote:

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with 6.10, the following does not typecheck:

foo `Control.Exception.catch` \ _ -> return bar

Ambiguous type variable `e' in the constraint: `Control.Exception.Exception e'

It is probably bad programming style anyway but what is the workaround?

As long as you're aware that it is bad programming style. We deliberately didn't include an easy way to do this, because we want people to think about why they need to catch *all* exceptions (most of the time it's a bug).

Since the above is bad form, what should I be doing? Could someone please provide some examples or point me at the list of exceptions that I can catch? What about catching multiple types of exceptions?

Thanks, Jason _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-users

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