The directory were in the path but Haskell\bin is before Haskell Platform\bin in the path and I had older versions of happy and alex in Haskell\bin. Still it would be nicer if all executables and all libraries were in the same place but this is minor issue. One more issue. When I am compiling Happy grammar I get warnings like the one bellow. This suggests that maybe the templates for Happy should be updated. templates\GenericTemplate.hs:110:15: Warning: Bindings containing unlifted types must use an outermost bang pattern: { new_state = (n Happy_GHC_Exts.-# (1# :: Happy_GHC_Exts.Int#)) } *** This will be an error in GHC 6.14! Fix your code now! In a case alternative: n -> happyShift new_state i tk st where new_state = (n Happy_GHC_Exts.-# (1# :: Happy_GHC_Exts.Int#)) In the expression: case action of { 0# -> happyFail i tk st -1# -> happyAccept i tk st n | (n Happy_GHC_Exts.<# (0# :: Happy_GHC_Exts.Int#)) -> (happyReduceArr Happy_Data_Array.! rule) i tk st where rule = (Happy_GHC_Exts.I# ((Happy_GHC_Exts.negateInt# ((n Happy_GHC_Exts.+# (1# :: Happy_GHC_Exts.Int#)))))) n -> happyShift new_state i tk st where new_state = (n Happy_GHC_Exts.-# (1# :: Happy_GHC_Exts.Int#)) } In the definition of `happyDoAction': happyDoAction i tk st = case action of { 0# -> happyFail i tk st -1# -> happyAccept i tk st n | (n Happy_GHC_Exts.<# (0# :: Happy_GHC_Exts.Int#)) -> (happyReduceArr Happy_Data_Array.! rule) i tk st where rule = (Happy_GHC_Exts.I# ((Happy_GHC_Exts.negateInt# ((n Happy_GHC_Exts.+# (1# :: Happy_GHC_Exts.Int#)))))) n -> happyShift new_state i tk st where new_state = (n Happy_GHC_Exts.-# (1# :: Happy_GHC_Exts.Int#)) } where off = indexShortOffAddr happyActOffsets st off_i = (off Happy_GHC_Exts.+# i) check = if (off_i Happy_GHC_Exts.>=# (0# :: Happy_GHC_Exts.Int#)) then (indexShortOffAddr happyCheck off_i Happy_GHC_Exts.==# i) else False action | check = indexShortOffAddr happyTable off_i | otherwise = indexShortOffAddr happyDefActions st