Proposal: Extensible exceptions

Isaac Dupree isaacdupree at
Sat Jul 5 20:17:27 EDT 2008

Bulat Ziganshin wrote:
> Hello Ian,
> Friday, July 4, 2008, 11:14:27 PM, you wrote:
>> If you import Control.OldException instead of Control.Exception then it
>> will be identical.
>> But fixing old code to work with the new library is very easy (e.g.
>> changing catch to catchAny if you get an ambiguous type variable), and
>> as Simon pointed out, places were you actually have to make changes
>> could do with being sanity checked anyway.
> so, all libs on hackage developed for 6.8 will become obsolete again? :)))

is it equally possible to put a NewException library for hackage 
ghc<6.9, providing those new function names that we introduce?  Would 
that help reduce gratuituous incompatibility, or would things still 
break too much, or is it just plain impossible because of module-naming 
and how base is fixed? :-)


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