Haskellers/Chris, As part of my quest to better understand STM and eventually build a concurrent haskell server app, I checked out an embryonic haskell mud demo from Chris Smith's repo. It seemed like a great sample app. But I ran into a build issue that seems to have to do with derive/TH. I am assuming this used to work, but something changed, either in TH itself or switching from ghc6.6 to ghc6.8. From the error message (below) I surmise either a) M.Map based values used to automagically work with derive/TH, but no longer do... in which case I need to create this instance manually or b) this should still work, more or less... but I have to import the map instance via an additional module, or something like that. Any advice? Thomas. ***** This is the error I am getting: thartman@thartman-laptop:~/mud>cat _darcs/prefs/defaultrepo http://cdsmith.twu.net/demos/mud thartman@thartman-laptop:~/mud>ghc --version The Glorious Glasgow Haskell Compilation System, version 6.8.2 thartman@thartman-laptop:~/mud>runghc Setup.lhs configure; runghc Setup.lhs build Configuring mud-0.1... Preprocessing executables for mud-0.1... Building mud-0.1... [2 of 5] Compiling World ( World.hs, dist/build/mud/mud-tmp/World.o ) World.hs:42:0: No instances for (Eq (a (M.Map String Player)), Eq (a (M.Map ItemId Item)), Eq (a (M.Map PlayerId Player)), Eq (a (M.Map RoomId Room)), Eq (a RoomId)) arising from the 'deriving' clause of a data type declaration at World.hs:(42,0)-(50,14) Possible fix: add an instance declaration for (Eq (a (M.Map String Player)), Eq (a (M.Map ItemId Item)), Eq (a (M.Map PlayerId Player)), Eq (a (M.Map RoomId Room)), Eq (a RoomId)) When deriving the instance for (Eq (World a))