Execution of DFAs

[mx-psi]

Current implementation of executeDFA has type:

executeDFA :: DFA -> [Alpha] -> Maybe [State]

The function returns a list of states in case there is a valid path for the word given or Nothing instead. This gives us no information about the path until we get to the non-valid symbol.

Should we change the implementation for getting the path until the non-valid symbol?

[mroman42]

Maybe we should consider:

execute :: a -> [Alpha] -> [m State]

instead of:

execute :: a -> [Alpha] -> m [State]

It seems coherent with the executeNFA type declaration and it may help to return the complete path, even if it finshes in a Nothing state.

[mx-psi]

If there is no path executeNFA will return [],which is equivalent to Nothing. We also obtain no information in this case. Hence we should change both functions in order to be consistent.

I'm not entirely convinced now that we are really going to use it. If we do it we would have to return [[Maybe State]] in the case of NFA and [Maybe State] for DFAs.

[mroman42]

I want to have the following type declarations in order to easily generalize the automata.

executeDFA :: DFA -> [Alpha] -> [Maybe State]
executeNFA :: NFA -> [Alpha] -> [[State]]

But, if it is necessary, we can change the types and think about generalizations later.