patch applied (ghc): Introduce an 'ExceptionMonad' class.

[Thomas Schilling]

Sun Sep 14 10:21:54 PDT 2008  Thomas Schilling <nominolo at googlemail.com>
  * Introduce an 'ExceptionMonad' class.
  
  This monad provides variants of 'catch', 'bracket', and 'finally', so
  exceptions can be handled in monads that wrap IO.  The latter two
  methods need to be part of the class definition, because GHC uses
  'block' and 'unblock' which are used in the definition of those two
  methods for the IO monad.  A perhaps better class interface would
  consist of 'gcatch', 'gblock', and 'gunblock' and let the latter two
  default to 'id' like is done for non-GHC implementations of 'bracket'
  and 'finally'.

    M ./compiler/utils/Exception.hs +73

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20080914172154-7c5c6-0005ffc797958c07d06689d90bffb3c2d7d749b4.gz