private void CreateNFA(string input)
{
Stack<char> operatorStack = new Stack<char>();
var expandedInput = ConcatExpand(input);
for (int i = 0; i < expandedInput.Length; i++)
{
char c = expandedInput[i];
if (char.IsLetterOrDigit(c))
Push(c);
else if (operatorStack.Count == 0)
operatorStack.Push(c);
else if (c == '(')
operatorStack.Push(c);
else if (c == ')')
{
while (operatorStack.Peek() != '(')
{
var op = operatorStack.Pop();
if (op == (char)8)
Concat();
else if (op == '*')
Star();
else if (op == '|')
Union();
else
return;
}
operatorStack.Pop(); //pop up '('
}
else
{
while (operatorStack.Count != 0 && Presedece(c, operatorStack.Peek()))
{
var op = operatorStack.Pop();
if (op == (char)8)
Concat();
else if (op == '*')
Star();
else if (op == '|')
Union();
else
return;
}
operatorStack.Push(c);
}
}
while (operatorStack.Count > 0)
{
var op = operatorStack.Pop();
if (op == (char)8)
Concat();
else if (op == '*')
Star();
else if (op == '|')
Union();
else
return;
}
if (_operandStack.Count == 0)
return;
var A = _operandStack.Pop();
A.GetLastState().AcceptState = true;
#if DEBUG
if (A.GetFirstState() != null)
{
using (var stream = File.OpenWrite("NFA.txt"))
{
using (var sw = new StreamWriter(stream))
{
HashSet<int> processedStates = new HashSet<int>();
Deque<State> unprocessedStates = new Deque<State>();
unprocessedStates.PushBack(A.GetFirstState());
while(unprocessedStates.Count>0)
{
var state = unprocessedStates.PopFront();
var labels = state.GetLabels();
foreach (var label in labels)
{
var destinationStates = state.GetStates(label);
if (destinationStates != null)
{
foreach (var dest in destinationStates)
{
sw.WriteLine("Start:" + state.ToString() + "," + "End:" + dest.ToString() + "," + "Label:" + (label!=EPSILON? label.ToString():"EPSILON"));
if (!processedStates.Contains(dest.StateId))
{
unprocessedStates.PushBack(dest);
}
}
}
}
processedStates.Add(state.StateId);
}
}
}
}
#endif
_NFA = A;
}
private void Push(Char input)
{
var state0 = new State(++_nextStateId);
var state1 = new State(++_nextStateId);
state0.AddTransition(input, state1);
FiniteStateAutomaton fsa = new FiniteStateAutomaton();
fsa.PushBack(state0);
fsa.PushBack(state1);
_operandStack.Push(fsa);
_inputSet.Add(input);
}
private void ConvertNFAToDFA()
{
if (_NFA == null)
return;
if (_DFA == null)
_DFA = new FiniteStateAutomaton();
_nextStateId = 0;
Stack<State> unmarkedStates = new Stack<State>();
HashSet<State> DFAStartStateSet = new HashSet<State>();
HashSet<State> NFAStartStateSet = new HashSet<State>();
NFAStartStateSet.Add(_NFA.GetFirstState());
DFAStartStateSet = EpsilonClosure(NFAStartStateSet);
var DFAStartState = new State(++_nextStateId, DFAStartStateSet);
_DFA.PushBack(DFAStartState);
unmarkedStates.Push(DFAStartState);
while (unmarkedStates.Count > 0)
{
var processingDFAState = unmarkedStates.Pop();
State dest = null;
foreach (var item in _inputSet)
{
var moveStates = Move(item, processingDFAState.NFAStatesSet);
var epsilonClosureStats = EpsilonClosure(moveStates);
bool found = false;
foreach (var s in _DFA.GetStates())
{
if (SameStatesSet(s.NFAStatesSet, epsilonClosureStats))
{
found = true;
dest = s;
break;
}
}
if (!found)
{
var newState = new State(++_nextStateId, epsilonClosureStats);
unmarkedStates.Push(newState);
_DFA.PushBack(newState);
processingDFAState.AddTransition(item, newState);
}
else
{
processingDFAState.AddTransition(item, dest);
}
}
}
}
