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tritaotritao
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Add DFA/NFA state machine utility code.
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6 files changed

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6 files changed

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‎src/Generator/Utils/FSM/ConsoleWriter.cs

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using System;
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namespace CppSharp.Utils.FSM{
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public class ConsoleWriter{
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public static void Failure(string message){
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Console.ForegroundColor = ConsoleColor.DarkRed;
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Write(message);
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}
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public static void Success(string message){
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Console.ForegroundColor = ConsoleColor.DarkGreen;
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Write(message);
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}
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private static void Write(string message){
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Console.WriteLine(message);
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Console.ResetColor();
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}
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}
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}

‎src/Generator/Utils/FSM/DFSM.cs

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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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namespace CppSharp.Utils.FSM
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{
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public class DFSM{
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public readonly List<string> Q = new List<string>();
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public readonly List<char> Sigma = new List<char>();
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public readonly List<Transition> Delta = new List<Transition>();
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public List<string> Q0 = new List<string>();
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public readonly List<string> F = new List<string>();
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public DFSM(IEnumerable<string> q, IEnumerable<char> sigma, IEnumerable<Transition> delta,
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IEnumerable<string> q0, IEnumerable<string> f){
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Q = q.ToList();
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Sigma = sigma.ToList();
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AddTransitions(delta);
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AddInitialStates(q0);
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AddFinalStates(f);
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}
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private void AddTransitions(IEnumerable<Transition> transitions){
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foreach (var transition in transitions.Where(ValidTransition)){
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Delta.Add(transition);
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}
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}
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private bool ValidTransition(Transition transition){
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return Q.Contains(transition.StartState) &&
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Q.Contains(transition.EndState) &&
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Sigma.Contains(transition.Symbol) &&
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!TransitionAlreadyDefined(transition);
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}
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private bool TransitionAlreadyDefined(Transition transition){
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return Delta.Any(t => t.StartState == transition.StartState &&
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t.Symbol == transition.Symbol);
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}
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private void AddInitialStates(IEnumerable<string> q0){
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foreach (var startingState in q0.Where(q => q != null && Q.Contains(q))){
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Q0.Add(startingState);
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}
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}
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private void AddFinalStates(IEnumerable<string> finalStates){
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foreach (var finalState in finalStates.Where(finalState => Q.Contains(finalState))){
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F.Add(finalState);
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}
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}
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public void Accepts(string input){
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ConsoleWriter.Success("Trying to parse: " + input);
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if (InvalidInputOrFSM(input)){
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return;
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}
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foreach (var q0 in Q0){
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var currentState = q0;
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var steps = new StringBuilder();
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foreach (var symbol in input.ToCharArray()){
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var transition = Delta.Find(t => t.StartState == currentState &&
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t.Symbol == symbol);
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if (transition == null){
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ConsoleWriter.Failure("No transitions for current state and symbol");
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ConsoleWriter.Failure(steps.ToString());
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continue;
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}
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currentState = transition.EndState;
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steps.Append(transition + "\n");
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}
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if (F.Contains(currentState)){
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ConsoleWriter.Success("Accepted the input with steps:\n" + steps);
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return;
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}
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ConsoleWriter.Failure("Stopped in state " + currentState +
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" which is not a final state.");
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ConsoleWriter.Failure(steps.ToString());
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}
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}
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private bool InvalidInputOrFSM(string input){
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if (InputContainsNotDefinedSymbols(input)){
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return true;
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}
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if (InitialStateNotSet()){
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ConsoleWriter.Failure("No initial state has been set");
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return true;
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}
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if (NoFinalStates()){
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ConsoleWriter.Failure("No final states have been set");
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return true;
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}
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return false;
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}
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private bool InputContainsNotDefinedSymbols(string input){
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foreach (var symbol in input.ToCharArray().Where(symbol => !Sigma.Contains(symbol))){
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ConsoleWriter.Failure("Could not accept the input since the symbol " + symbol + " is not part of the alphabet");
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return true;
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}
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return false;
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}
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private bool InitialStateNotSet(){
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return Q0.Count == 0;
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}
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private bool NoFinalStates(){
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return F.Count == 0;
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}
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public void RemoveUnreachableStates(){
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var reachableStates = new HashSet<string>(Q0);
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var newStates = new HashSet<string>(Q0);
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do{
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var temp = new HashSet<string>();
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foreach (var q in newStates){
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var reachableFromQ = Delta.FindAll(t => t.StartState == q).Select(t => t.EndState);
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temp.UnionWith(reachableFromQ);
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}
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temp.ExceptWith(reachableStates);
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newStates = temp;
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reachableStates.UnionWith(newStates);
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} while (newStates.Count > 0);
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var unreachableStates = Q.Where(q => !reachableStates.Contains(q));
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for (int i = Delta.Count - 1; i > 0; i--){
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var transition = Delta[i];
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if (unreachableStates.Contains(transition.EndState) ||
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unreachableStates.Contains(transition.StartState)){
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Delta.Remove(transition);
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}
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}
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foreach (var unrechableState in unreachableStates){
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Q.Remove(unrechableState);
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}
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}
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}
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}

‎src/Generator/Utils/FSM/Minimize.cs

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using System.Collections.Generic;
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using System.Linq;
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namespace CppSharp.Utils.FSM{
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internal class Minimize{
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public static DFSM MinimizeDFSM(DFSM fsm){
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var reversedNDFSM = Reverse(fsm);
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var reversedDFSM = PowersetConstruction(reversedNDFSM);
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var NDFSM = Reverse(reversedDFSM);
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return PowersetConstruction(NDFSM);
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}
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private static NDFSM Reverse(DFSM d){
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var delta = new List<Transition>();
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foreach (var transition in d.Delta){
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delta.Add(new Transition(transition.EndState, transition.Symbol, transition.StartState));
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}
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return new NDFSM(d.Q, d.Sigma, delta, d.F, d.Q0);
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}
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public static DFSM PowersetConstruction(NDFSM ndfsm){
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var Q = new List<string>();
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var Sigma = ndfsm.Sigma.ToList();
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var Delta = new List<Transition>();
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var Q0 = new List<string> { string.Join(" ", ndfsm.Q0) };
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var F = new List<string>();
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var processed = new List<string>();
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var queue = new Queue<string>();
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queue.Enqueue(string.Join(",", ndfsm.Q0));
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while (queue.Count > 0){
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var setState = queue.Dequeue();
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processed.Add(setState);
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Q.Add(CleanupState(setState));
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var statesInCurrentSetState = setState.Split(',').ToList();
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foreach (var state in statesInCurrentSetState){
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if (ndfsm.F.Contains(state)){
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F.Add(CleanupState(setState));
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break;
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}
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}
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var symbols = ndfsm.Delta
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.Where(t => statesInCurrentSetState.Contains(t.StartState))
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.Select(t => t.Symbol)
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.Distinct();
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foreach (var symbol in symbols){
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var reachableStates =
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ndfsm.Delta
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.Where(t => t.Symbol == symbol &&
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statesInCurrentSetState.Contains(t.StartState))
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.OrderBy(t => t.EndState).
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Select(t => t.EndState);
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var reachableSetState = string.Join(",", reachableStates);
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Delta.Add(new Transition(CleanupState(setState), symbol, CleanupState(reachableSetState)));
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if (!processed.Contains(reachableSetState)){
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queue.Enqueue(reachableSetState);
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}
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}
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}
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return new DFSM(Q, Sigma, Delta, Q0, F);
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}
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private static string CleanupState(string state){
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return state.Replace(",", " ");
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}
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}
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}

‎src/Generator/Utils/FSM/NDFSM.cs

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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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namespace CppSharp.Utils.FSM{
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public class NDFSM{
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private readonly List<string> Q = new List<string>();
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public readonly List<char> Sigma = new List<char>();
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public readonly List<Transition> Delta = new List<Transition>();
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public List<string> Q0 = new List<string>();
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public readonly List<string> F = new List<string>();
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public NDFSM(IEnumerable<string> q, IEnumerable<char> sigma,
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IEnumerable<Transition> delta, IEnumerable<string> q0, IEnumerable<string> f){
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Q = q.ToList();
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Sigma = sigma.ToList();
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AddTransitions(delta);
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AddInitialStates(q0);
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AddFinalStates(f);
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}
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private void AddTransitions(IEnumerable<Transition> transitions){
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foreach (var transition in transitions.Where(ValidTransition)){
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Delta.Add(transition);
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}
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}
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private bool ValidTransition(Transition transition){
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return Q.Contains(transition.StartState) &&
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Q.Contains(transition.EndState) &&
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Sigma.Contains(transition.Symbol);
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}
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private void AddInitialStates(IEnumerable<string> q0){
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foreach (var startingState in q0.Where(q => q != null && Q.Contains(q))){
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Q0.Add(startingState);
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}
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}
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private void AddFinalStates(IEnumerable<string> finalStates){
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foreach (var finalState in finalStates.Where(finalState => Q.Contains(finalState))){
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F.Add(finalState);
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}
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}
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public void Accepts(string input){
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ConsoleWriter.Success("Trying to accept: " + input);
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if (Q0.Any(q0 => Accepts(q0, input, new StringBuilder()))){
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return;
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}
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ConsoleWriter.Failure("Could not accept the input: " + input);
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}
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private bool Accepts(string currentState, string input, StringBuilder steps){
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if (input.Length > 0){
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var transitions = GetAllTransitions(currentState, input[0]);
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foreach (var transition in transitions){
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var currentSteps = new StringBuilder(steps.ToString() + transition);
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if (Accepts(transition.EndState, input.Substring(1), currentSteps)){
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return true;
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}
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}
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return false;
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}
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if (F.Contains(currentState)){
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ConsoleWriter.Success("Successfully accepted the input " + input + " " +
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"in the final state " + currentState +
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" with steps:\n" + steps);
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return true;
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}
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return false;
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}
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private IEnumerable<Transition> GetAllTransitions(string currentState, char symbol){
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return Delta.FindAll(t => t.StartState == currentState &&
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t.Symbol == symbol);
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}
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}
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}

‎src/Generator/Utils/FSM/Program.cs

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using System.Collections.Generic;
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namespace CppSharp.Utils.FSM{
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internal class Program{
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private static void Main(string[] args){
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var Q = new List<string>{"q0", "q1"};
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var Sigma = new List<char>{'0', '1'};
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var Delta = new List<Transition>{
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new Transition("q0", '0', "q0"),
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new Transition("q0", '1', "q1"),
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new Transition("q1", '1', "q1"),
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new Transition("q1", '0', "q0")
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};
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var Q0 = new List<string>{"q0"};
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var F = new List<string>{"q0", "q1"};
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var DFSM = new DFSM(Q, Sigma, Delta, Q0, F);
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var minimizedDFSM = Minimize.MinimizeDFSM(DFSM);
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}
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}
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}

‎src/Generator/Utils/FSM/Transition.cs

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namespace CppSharp.Utils.FSM{
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public class Transition{
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public string StartState { get; private set; }
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public char Symbol { get; private set; }
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public string EndState { get; private set; }
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public Transition(string startState, char symbol, string endState){
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StartState = startState;
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Symbol = symbol;
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EndState = endState;
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}
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public override string ToString(){
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return string.Format("({0}, {1}) -> {2}\n", StartState, Symbol, EndState);
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}
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}
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}
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