Generalize newStates

[mroman42]

newStates is an auxiliary function for listStates. Its type may be generalizable to:

(Automata a) => a -> State -> [State]

But to generalize its type, we would need to create a function whose particular cases for [] and Maybe were catMaybes and concat, as we can see here (from ToGraph.hs):

listStates :: DFA -> [State]
listStates dfa = stabilize (nub . concat . (map (newStates dfa))) [fromJust (initialDFA dfa)]

newStates :: DFA -> State -> [State]
newStates dfa s = s : catMaybes [(deltaDFA dfa) s a | a <- (alphaDFA dfa)]

listStatesNfa :: NFA -> [State]
listStatesNfa nfa = stabilize (nub . concat . (map (newStatesNfa nfa))) (initialNFA nfa)

newStatesNfa :: NFA -> State -> [State]
newStatesNfa nfa s = s : concat [(deltaNFA nfa) s a | a <- (alphaNFA nfa)]

[mx-psi]

I think the simplest solution is using toNFA function to convert the automata given as input to an NFA (or the most general type if we have a more general one) and define

listStates :: (Automata a m) => a -> State -> [State]
listStates = listStatesNfa . toNFA

as the general function. Since Graphviz doesn't care about the type of the automaton, this solution is valid for both types.