/// <summary>
/// Initializes a DFA and generates all the states and transitions given a NFA
/// </summary>
/// <param name="nfa">NFA from which the DFA will be populated</param>
public DFA(NFA <T> nfa)
: base()
{
List <T> symbols = nfa.Symbols;
this.BuildSubset(nfa, nfa.InitialState);
}
/// <summary>
/// Performs the concatenation of two NFA's
/// </summary>
/// <param name="nfa">NFA to be concatenated</param>
/// <returns>The concatenated NFA</returns>
public NFA <T> And(NFA <T> nfa)
{
NFA <T> result = this.Clone() as NFA <T>;
NFA <T> andparcel = nfa.Clone() as NFA <T>;
int nextavail = result.NextAvailableState;
andparcel.OffsetStates(nextavail - 1);
result.Transitions.AddRange(andparcel.Transitions);
result.AcceptingStates.Clear();
result.AcceptingStates.AddRange(andparcel.AcceptingStates);
return(result);
}
/// <summary>
/// Performs the alternation of two NFA's
/// </summary>
/// <param name="nfa">NFA to be alternation</param>
/// <returns>The alternation NFA</returns>
public NFA <T> Or(NFA <T> nfa)
{
NFA <T> result = this.Clone() as NFA <T>;
NFA <T> orparcel = nfa.Clone() as NFA <T>;
int nextavail = result.NextAvailableState;
//first state will be reconverted (avoid state number loss)
orparcel.OffsetStates(nextavail - 1);
orparcel.RenumberState(orparcel.InitialState, result.InitialState);
orparcel.RenumberState(orparcel.AcceptingStates[0], result.AcceptingStates[0]);
result.Transitions.AddRange(orparcel.Transitions);
return(result);
}
/// <summary>
/// Performs the kleene/star operation of the NFA
/// </summary>
/// <returns>The kleene/star NFA</returns>
public NFA <T> Kleene()
{
NFA <T> result = this.Clone() as NFA <T>;
result.OffsetStates(1);
int nextavail = result.NextAvailableState;
result.Transitions.Add(new Transition <T>(0, this.Epsilon, 1));
result.Transitions.Add(new Transition <T>(result.AcceptingStates[0], this.Epsilon, nextavail));
result.Transitions.Add(new Transition <T>(nextavail, this.Epsilon, 1));
result.Transitions.Add(new Transition <T>(0, this.Epsilon, nextavail));
result.AcceptingStates.Clear();
result.AcceptingStates.Add(nextavail);
result.InitialState = 0;
return(result);
}
/// <summary>
/// Implementation of the IClonable interface
/// </summary>
/// <returns>Returns a clone of the NFA object</returns>
public object Clone()
{
NFA <T> result = new NFA <T>(this.Epsilon);
result.Transitions.Clear();
foreach (Transition <T> t in this.Transitions)
{
Transition <T> clonet = new Transition <T>(t.PreviousState, t.Symbol, t.NextState);
if (!result.Transitions.Contains(clonet))
{
result.Transitions.Add(new Transition <T>(t.PreviousState, t.Symbol, t.NextState));
}
}
result.AcceptingStates.AddRange(this.AcceptingStates.ToArray());
result.InitialState = this.InitialState;
return(result);
}
/// <summary>
/// Performs the replacement of all Transitions given a symbol by a full NFA
/// </summary>
/// <param name="symbol">Generic type T value of the trigger to be replaced</param>
/// <param name="replacement">The NFA be inserted</param>
/// <returns>A NFA with all the replacemente in place</returns>
public NFA <T> ReplaceTransitions(T symbol, NFA <T> replacement)
{
NFA <T> result = this.Clone() as NFA <T>;
for (int i = 0; i < result.Transitions.Count; i++)
{
if (result.Transitions[i].Symbol.CompareTo(symbol) == 0)
{
NFA <T> insert = replacement.Clone() as NFA <T>;
insert.OffsetStates(result.NextAvailableState);
insert.RenumberState(insert.InitialState, result.Transitions[i].PreviousState);
insert.RenumberState(insert.AcceptingStates[0], result.Transitions[i].NextState);
result.Transitions.AddRange(insert.Transitions);
result.Transitions.RemoveAt(i);
i--;
}
}
return(result);
}
/// <summary>
/// Performs the NFA to DFA convertion (recursive)
/// </summary>
/// <param name="nfa">The NFA object to convert</param>
/// <param name="start">The strting state</param>
private void BuildSubset(NFA <T> nfa, int start)
{
Stack <List <int> > unprocessedSubsets = new Stack <List <int> >();
int availableState = 0;
List <int> startPoint = nfa.EpsilonClosure(start);
unprocessedSubsets.Push(startPoint);
_SubSets[startPoint] = availableState++;
if (startPoint.Contains(nfa.AcceptingStates[0]) && !this.AcceptingStates.Contains(_SubSets[startPoint]))
{
this.AcceptingStates.Add(_SubSets[startPoint]);
}
while (unprocessedSubsets.Count > 0)
{
List <int> subset = unprocessedSubsets.Pop();
for (int i = 0; i < subset.Count; i++)
{
foreach (T symbol in nfa.Symbols)
{
int nextstate = nfa.GetNextState(subset[i], symbol);
if (nextstate >= 0)
{
List <int> newsubset = nfa.EpsilonClosure(nextstate);
if (!_SubSets.ContainsKey(newsubset))
{
unprocessedSubsets.Push(newsubset);
_SubSets[newsubset] = availableState++;
}
this.Transitions.Add(new Transition <T>(_SubSets[subset], symbol, _SubSets[newsubset]));
if (newsubset.Contains(nfa.AcceptingStates[0]) && !this.AcceptingStates.Contains(_SubSets[newsubset]))
{
this.AcceptingStates.Add(_SubSets[newsubset]);
}
}
}
}
}
}
