Error when using Control.Exception.handle

[Alexey Kamenev]

Hello,
I'm getting the following error when trying to use handle function
(Ch8, p. 209):

:t handle (const (return []))

<interactive>:1:0:
Ambiguous type variable `e' in the constraint:
`Exception e'
arising from a use of `handle' at <interactive>:1:0-25
Probable fix: add a type signature that fixes these type variable
(s)

listMatches code fails with
Ambiguous type variable `e' in the constraint:
`GHC.Exception.Exception e'
arising from a use of `handle'

Note that when I use catch everything is fine. I've tried playing with
hiding etc but it did not work.
Is there something I'm doing wrong?
GHC 6.10.1

Thank you.

[Don Stewart]

The exception interface changed between GHC 6.8.x and GHC 6.10.x

RWH uses the old interface. This is available in two ways to 6.10
users:

* via Control.OldException, using the module system
* by using --constraint="base < 4" if building with cabal.

-- Don

[Alexey Kamenev]

Thank you for the reply - Control.OldException worked just fine.

I've got one more question (it maybe stupid, but anyway): where can I
read about extensible exceptions? I've found only release notes
mentioning that old style will be removed in next versions of GHC and
couple of wiki pages (http://haskell.org/haskellwiki/Exception,
http://hackage.haskell.org/trac/haskell-prime/wiki/ExtensibleExceptions)
but not sure I got it right.

Thanks.