Hi, I'm currently trying to have Hood work with GHC, but I have some problems - I have succeeded in using the hugs version of Hood - I have dowloaded the GHC version (slightly different) but the compilation of the 'Observe' modules fails (the module is supposed to work with GHC 4.08 and I have GHC 5.00.2) : Duplicate instance declarations: Observe.lhs:272: Observable IOError Observe.lhs:291: Observable Exception with the following command-line : ghc -fglasgow-exts -package lang -package concurrent Observe.lhs corresponding to the source : instance Observable IOError where { observer = observeBase } instance Observable Exception where observer (IOException a) = send "IOException" (return IOException << a) observer (ErrorCall a) = send "ErrorCall" (return ErrorCall << a) observer other = send "<Exception>" (return other) I don't understant why there are duplicate instance declarations. Furthermore, removing them leads to : Observe.lhs:182: No instance for `Observable Exception' arising from use of `<<' at Observe.lhs:182 In the second argument of `send', namely `((return throw) << exc)' In the first argument of `return', namely `(send "throw" ((return throw) << exc) context)' Changing names (of Observable...) does not help, so its is not a name conflict with prelude or libraries The source is avalaible at : http://haskell.cs.yale.edu/hood/downloads/ghc/Observe.lhs (I don't include it here so the M.L. won't be cluttered) If somebody can help, I am completely at a loss Alain