public DfaTransitionDiagram minimizeStates()
{
List <List <State> > pi = new List <List <State> >();
//initialize pi
pi.Add(this.finalStates);
List <State> temp = new List <State>();
//find non final states
foreach (State s in this.states)
{
if (s.type == stateType.intermediate || s.type == stateType.initial)
{
temp.Add(s);
}
}
if (temp.Count != 0)
{
pi.Add(temp);
}
//now pi has two sets: finals and non-finals
if (pi.Count == 1) // i.e. pi has only one set because all the states are either final or both (initial & final)
{
MessageBox.Show("The diagram is already minimized");
return(this);
}
DfaTransitionDiagram newDiagram = new DfaTransitionDiagram();
newDiagram.inputs = this.inputs;
newDiagram.noOfInputs = this.noOfInputs;
newDiagram.setCanvas(canvasMain);
List <List <State> > newPi = pi; // for the initial condition
List <List <State> > set;
while (true)
{
pi = newPi;
set = pi;
List <List <State> > piTemp = null;
foreach (String input in inputs)
{
piTemp = new List <List <State> >();
foreach (List <State> ls in set)
{
if (ls.Count == 1)
{
//beacuse if a set contains only a single item then it will remain single
piTemp.Add(new List <State>());
piTemp.Last().Add(ls[0]);
continue;
}
List <int> abc = new List <int>();
foreach (State s in ls)
{
State stt = table[s.index, getIndexOfInput(input)];
if (stt == null)
{
MessageBox.Show("To minimize a DFA, For each State you must define transitions for all input symbols");
return(null);
}
else
{
abc.Add(piTemp.Count + getSetIndex(pi, stt));
}
}
//pitemp.count is added because before that it was problematic for the iteration
//with the next set on same input symbol due to same 0 1 etc in abc
for (int i = 0; i < abc.Count; i++)
{
piTemp.Add(new List <State>());
}
while (piTemp.Count <= abc.Max())
{
piTemp.Add(new List <State>());
}
int j = 0;
foreach (int i in abc)
{
piTemp[i].Add(ls[j]);
j++;
}
// remove empty lists
List <List <State> > t = new List <List <State> >(); // to bypass the collection modified error
foreach (List <State> ls2 in piTemp)
{
if (ls2.Count == 0)
{
t.Add(ls2);
}
}
foreach (List <State> ls2 in t)
{
piTemp.Remove(ls2);
}
}
set = piTemp;
}
newPi = piTemp;
if (isPiEqualsNewPi(pi, newPi))
{
break;
}
}
canvasMain.Children.Clear();
// now create a new diagram by taking states from pi
foreach (List <State> ls in pi)
{
State s = newDiagram.addState(State.getNewStatePosition());
s.figure.ToolTip = getToolTip(ls);
if (containsInitialState(ls))
{
s.addStartingArrow(canvasMain);
newDiagram.initialStates.Add(s);
s.type = stateType.initial;
if (containsFinalState(ls))
{
s.type = stateType.both;
newDiagram.finalStates.Add(s);
s.figure.Stroke = Brushes.Black;
s.figure.StrokeThickness = 2;
}
}
else if (containsFinalState(ls))
{
s.type = stateType.final;
newDiagram.finalStates.Add(s);
s.figure.Stroke = Brushes.Black;
s.figure.StrokeThickness = 2;
}
}
foreach (List <State> ls in pi)
{
State source = ls[0];
foreach (string input in newDiagram.inputs)
{
State dest = table[ls[0].index, getIndexOfInput(input)];
if (dest != null)
{
source = getStateByToolTip(newDiagram, getToolTip(ls));
foreach (List <State> ls2 in pi)
{
if (ls2.Contains(dest))
{
dest = getStateByToolTip(newDiagram, getToolTip(ls2));
break;
}
}
if (source != null && dest != null)
{
Transition tr = newDiagram.addTransition(source, dest);
if (tr != null)
{
((ComboBox)((StackPanel)tr.figure.Tag).Children[0]).SelectedItem = input;
}
}
}
}
}
//code inserted later to patch the flaws in algorithm
bool isDeletedSomeState = true;
while (isDeletedSomeState)
{
isDeletedSomeState = false;
bool isOrphanState;
List <State> tmp = new List <State>(newDiagram.states);
foreach (State s in tmp)
{
isOrphanState = true;
bool hasSource = false, hasDest = false;
foreach (Transition t in s.transitions)
{
if (s.type == stateType.initial || s.type == stateType.final || s.type == stateType.both)
{
isOrphanState = false;
break;
}
if (t.destState.index == s.index)
{
hasDest = true;
}
if (t.sourceState.index == s.index)
{
hasSource = true;
}
if (hasSource && hasDest)
{
isOrphanState = false;
break;
}
}
if (isOrphanState)
{
newDiagram.selectedState = s;
newDiagram.deleteState();
isDeletedSomeState = true;
}
}
}
return(newDiagram);
}
public DfaTransitionDiagram convertToDfa()
{
NfaTransitionDiagram diagram = this.removeNullMoves();
DfaTransitionDiagram newDiagram = new DfaTransitionDiagram();
newDiagram.setCanvas(canvasMain);
canvasMain.Children.Clear();
newDiagram.inputs = diagram.inputs;
newDiagram.noOfInputs = diagram.noOfInputs;
State.resetPoints(); // because the some state positions have been consumed by removeNullMoves(), so reset them
//add the initial state
State iState = newDiagram.addState(State.getNewStatePosition());
iState.addStartingArrow(canvasMain);
iState.type = diagram.initialStates[0].type;
newDiagram.initialStates.Add(iState);
if (iState.type == stateType.both)
{
newDiagram.finalStates.Add(iState);
iState.figure.Stroke = Brushes.Black;
iState.figure.StrokeThickness = 2;
}
iState.figure.ToolTip = diagram.initialStates[0].figure.ToolTip;
newDiagram.selectedState = iState;
List <List <State> > newStates = new List <List <State> >();
List <State> temp = new List <State>();
temp.Add(iState);
newStates.Add(temp);
string tooltip;
int i = -1;
while (i < newStates.Count - 1)
{
List <State> currentState = newStates[++i];
newDiagram.selectedState = getStateByToolTip(newDiagram, getToolTip(currentState));
foreach (string input in newDiagram.inputs)
{
List <State> nextState = new List <State>();
foreach (State s in currentState)
{
if (diagram.table[s.index, diagram.getIndexOfInput(input)] != null)
{
foreach (State t in diagram.table[s.index, diagram.getIndexOfInput(input)])
{
if (!nextState.Contains(t))
{
nextState.Add(t);
}
}
}
}
tooltip = getToolTip(nextState);
if (tooltip != "")
{
State x = getStateByToolTip(newDiagram, tooltip);
if (x == null) //nextState do not exists in the newStates or newDiagram.States
{
// a new state is found
State s = newDiagram.addState(State.getNewStatePosition());
s.figure.ToolTip = tooltip;
if (containsFinalState(nextState))
{
s.type = stateType.final;
newDiagram.finalStates.Add(s);
s.figure.Stroke = Brushes.Black;
s.figure.StrokeThickness = 2;
}
Point pt1 = new Point();
Random rnd = new Random();
pt1.X = (double)rnd.Next((int)canvasMain.ActualWidth);
pt1.X = (double)rnd.Next((int)canvasMain.ActualHeight);
Transition tr = newDiagram.addTransition(newDiagram.selectedState, s, pt1.ToString());
((ComboBox)((StackPanel)tr.figure.Tag).Children[0]).SelectedItem = input;
newStates.Add(nextState);
}
else
{
Transition tr = newDiagram.addTransition(newDiagram.selectedState, x);
if (tr != null)
{
((ComboBox)((StackPanel)tr.figure.Tag).Children[0]).SelectedItem = input;
}
}
}
}
}
return(newDiagram);
}
