A simple DFA implemented in Prolog

dfa.pl

dfa_start(dfa1, q0).
dfa_final(dfa1, q3).

dfa_transition(dfa1, q0, '0', q1).
dfa_transition(dfa1, q0, '1', q1).
dfa_transition(dfa1, q0, '.', q2).
dfa_transition(dfa1, q1, '0', q1).
dfa_transition(dfa1, q1, '1', q1).
dfa_transition(dfa1, q1, '.', q3).
dfa_transition(dfa1, q2, '0', q3).
dfa_transition(dfa1, q2, '1', q3).
dfa_transition(dfa1, q2, '.', q4).
dfa_transition(dfa1, q3, '0', q3).
dfa_transition(dfa1, q3, '1', q3).
dfa_transition(dfa1, q3, '.', q4).
dfa_transition(dfa1, q4, '0', q4).
dfa_transition(dfa1, q4, '1', q4).
dfa_transition(dfa1, q4, '.', q4).

allStates(DFA, States) :-
    findall([F,T], dfa_transition(DFA, F, _, T), Transitions), 
    flatten(Transitions, FlatTransitions),
    list_to_set(FlatTransitions, States).

dfaAccept(DFA, InputStr) :-
    dfa_start(dfa1, CurrentState),
    string_to_list(InputStr, StrList),
    dfaAccept(DFA, StrList, CurrentState),
    !.

dfaAccept(DFA, [H|T], CurrentState) :-
    char_code(Letter, H),
    dfa_transition(DFA, CurrentState, Letter, NextState),
    % format('DFA: ~w, CurrentState: ~w, Letter: ~w, NextState: ~w', [DFA, CurrentState, Letter, NextState]), nl,
    dfaAccept(DFA, T, NextState).

dfaAccept(DFA, [ ], CurrentState) :- 
    % format('LastState: ~w', [CurrentState]), nl,
    dfa_final(DFA, CurrentState),
    !.

?- [dfa].
true.

?- dfaAccept(dfa1, '1.0').
true.

?- dfaAccept(dfa1, '1.0.1').
false.