/// <summary>
/// Creates and initializes a minimal automaton with an entry state and a separate exit state
/// </summary>
/// <returns>The created automaton</returns>
public static NFA NewMinimal()
{
NFA result = new NFA();
result.StateEntry = result.AddNewState();
result.StateExit = result.AddNewState();
return(result);
}
/// <summary>
/// Creates an automaton that is the difference between the left and right sub-automata
/// </summary>
/// <param name="left">The left automaton</param>
/// <param name="right">The right automaton</param>
/// <param name="useClones">True to completely clone the sub-automata</param>
/// <returns>The new automaton</returns>
// TODO: should get rid of static methods
public static NFA NewDifference(NFA left, NFA right, bool useClones)
{
NFA final = NewMinimal();
NFAState statePositive = final.AddNewState();
NFAState stateNegative = final.AddNewState();
statePositive.Mark = 1;
stateNegative.Mark = -1;
if (useClones)
{
left = left.Clone(true);
right = right.Clone(true);
}
final.states.AddRange(left.states);
final.states.AddRange(right.states);
final.StateEntry.AddTransition(NFA.EPSILON, left.StateEntry);
final.StateEntry.AddTransition(NFA.EPSILON, right.StateEntry);
left.StateExit.AddTransition(NFA.EPSILON, statePositive);
right.StateExit.AddTransition(NFA.EPSILON, stateNegative);
statePositive.AddTransition(NFA.EPSILON, final.StateExit);
final.StateExit.AddItem(DummyItem.Instance);
DFA equivalent = new DFA(final);
equivalent.Prune();
final = new NFA(equivalent);
final.StateExit = final.AddNewState();
foreach (NFAState state in final.states)
{
if (state.Items.Contains(DummyItem.Instance))
{
state.ClearItems();
state.AddTransition(NFA.EPSILON, final.StateExit);
}
}
return(final);
}
