* Maxime Henrion
Anyone knows what I'm doing wrong here? I suspect my attempt at having self-referential data is somehow buggy; do I need to treat transitions to the same state differently?
The problem is that when you call 'self', you record *that* state of your DFA in the map. When DFA gets updated further, the recorded self-reference is not updated appropriately. In your case a workaround is to call 'self' after all the other updates, i.e. test :: String -> Bool test = accept s1 where s1 = self '1' . path '0' s2 $ empty True s2 = self '1' . path '0' s1 $ empty False But I don't see why you need 'self' at all -- you can just use path as with any other type of transition: test :: String -> Bool test = accept s1 where s1 = path '0' s2 . path '1' s1 $ empty True s2 = path '0' s1 . path '1' s2 $ empty False -- Roman I. Cheplyaka :: http://ro-che.info/ Don't worry what people think, they don't do it very often.