[Haskell-cafe] Haskell on Debian

Daniel Fischer daniel.is.fischer at web.de
Mon Apr 5 11:46:25 EDT 2010

Am Montag 05 April 2010 17:39:29 schrieb Alex Rozenshteyn:
> I did try that; after adding a bunch of packages to the .cabal file and
> trying to build i get this:
> [ 1 of 81] Compiling Plugin.Dict.DictLookup ( Plugin/Dict/DictLookup.hs,
> dist/build/lambdabot/lambdabot-tmp/Plugin/Dict/DictLookup.o )
> Plugin/Dict/DictLookup.hs:33:4:
>     Ambiguous type variable `e' in the constraint:
>       `GHC.Exception.Exception e'
>         arising from a use of `handle' at
> Plugin/Dict/DictLookup.hs:33:4-42 Probable fix: add a type signature
> that fixes these type variable(s) cabal: Error: some packages failed to
> install:
> lambdabot- failed during the building phase. The exception was:
> ExitFailure 1

Looks like it was written for the old Control.Exception.

You can

a) change the import to import Control.OldException (handle)

b) add a type signature in that line, e.g.
    handle (\(e :: SomeException) -> ...)
if you don't know what types of exceptions to expect

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