public static void TestRegExp()
{
a = new Regex("a");
b = new Regex("b");
// expr1: "baa"
expr1 = new Regex("baa");
// expr2: "bb"
expr2 = new Regex("bb");
// expr3: "baa | baa"
expr3 = expr1.or(expr2);
// all: "(a|b)*"
all = (a.or(b)).star();
// expr4: "(baa | baa)+"
expr4 = expr3.plus();
// expr5: "(baa | baa)+ (a|b)*"
expr5 = expr4.dot(all);
// converting to NDFA
int i = 0;
NDFA <int, char> ndfa = expr5.toNDFA(ref i);
string ndfaTest = "baab";
tester(ndfaTest, ndfa.accept(ndfaTest.ToCharArray()));
Console.WriteLine("-----NDFA Graph-----");
GraphViz.PrintNDFA(ndfa, "ndfa");
}
public NDFA <T, U> reverse(U epsilon)
{
NDFA <T, U> result = new NDFA <T, U>(epsilon);
// Add DFA's startstate as endstate
result.addEndState(StartState);
foreach (T endState in EndStates)
{
result.addStartState(endState);
}
forEachTransition((terminal, fromState, toState)
=> result.addTransition(terminal, toState, fromState));
return(result);
}
public static void PrintNDFA <T, U>(NDFA <T, U> ndfa, string filename)
{
var s = "digraph{ ";
s += GetFinalStatesData(ndfa.EndStates);
s += GetStartStatesData(ndfa.StartStates);
s += "node [shape = circle];";
ndfa.forEachTransition((terminal, fromState, toState) => s += TransitionToString(terminal, fromState, toState));
s += " }";
Console.WriteLine(s);
GenerateGraphFile(s, filename, Enums.GraphReturnType.Svg);
}
public NDFA <int, char> toNDFA(ref int i)
{
NDFA <int, char> ndfaLeft = left?.toNDFA(ref i);
NDFA <int, char> ndfaRight = right?.toNDFA(ref i);
var ndfa = new NDFA <int, char>('$', ndfaLeft, ndfaRight);
switch (op)
{
case Operator.ONE:
var currState = ++i;
ndfa.addStartState(currState);
foreach (var terminal in terminals)
{
ndfa.addTransition(terminal, currState, currState = ++i);
}
ndfa.addEndState(currState);
break;
case Operator.OR:
var orStartState = ++i;
var orEndState = ++i;
ndfa.addStartState(orStartState);
ndfa.addTransition(ndfa.Epsilon, orStartState, ndfaLeft.StartStates.First());
ndfa.addTransition(ndfa.Epsilon, orStartState, ndfaRight.StartStates.First());
ndfa.addTransition(ndfa.Epsilon, ndfaLeft.EndStates.Last(), orEndState);
ndfa.addTransition(ndfa.Epsilon, ndfaRight.EndStates.Last(), orEndState);
ndfa.addEndState(orEndState);
break;
case Operator.DOT:
ndfa.addStartState(ndfaLeft.StartStates.First());
ndfa.addEndState(ndfaRight.EndStates.Last());
ndfa.addTransition(ndfa.Epsilon, ndfaLeft.EndStates.Last(), ndfaRight.StartStates.First());
break;
case Operator.PLUS:
ndfa = plusAndStarOperatorHandlerCalledByToNDFA(ndfa, ndfaLeft, ref i);
break;
case Operator.STAR:
ndfa = plusAndStarOperatorHandlerCalledByToNDFA(ndfa, ndfaLeft, ref i);
break;
default:
break;
}
return(ndfa);
}
private NDFA <int, char> plusAndStarOperatorHandlerCalledByToNDFA(NDFA <int, char> ndfa, NDFA <int, char> left, ref int i)
{
var startState = ++i;
var endState = ++i;
ndfa.addStartState(startState);
ndfa.addEndState(endState);
ndfa.addTransition(ndfa.Epsilon, startState, left.StartStates.First());
ndfa.addTransition(ndfa.Epsilon, left.EndStates.Last(), left.StartStates.First());
ndfa.addTransition(ndfa.Epsilon, left.EndStates.Last(), endState);
if (op == Operator.STAR)
{
ndfa.addTransition(ndfa.Epsilon, startState, endState);
}
return(ndfa);
}
public NDFA(U epsilon, NDFA <T, U> ndfa1, NDFA <T, U> ndfa2)
{
Epsilon = epsilon;
if (ndfa1 != null)
{
Alphabet.UnionWith(ndfa1.Alphabet);
}
if (ndfa2 != null)
{
Alphabet.UnionWith(ndfa2.Alphabet);
}
Transitions
= ndfa1 != null && ndfa2 != null
? ndfa1.Transitions.Concat(ndfa2.Transitions).ToDictionary(kvp => kvp.Key, kvp => kvp.Value)
: ndfa1 != null
? ndfa1.Transitions
: ndfa2 != null
? ndfa2.Transitions
: Transitions;
}
