/// <summary>
/// Executes the "?" operator by creating a split state that allows to either
/// go through the NFA or not.
/// </summary>
/// <param name="operandStack">The operand stack to execute the operator on</param>
public void Execute(Stack<NFAFragment> operandStack)
{
//Pop the needed NFA
NFAFragment nfa1 = operandStack.Pop();
//Create the split state
NFASplitState splitState = new NFASplitState(nfa1.startState, null);
//The beginning of the NFA is now the split state
nfa1.startState = splitState;
//Add the split state to the list of unbound states
nfa1.unboundStates.Add(splitState);
//Push the resultant NFA into stack
operandStack.Push(nfa1);
}
/// <summary>
/// Executes the "*" operator by creating a split state which allows to either go through the NFA or continue
/// The exits from the NFA will lead back to this state
/// Result - zero or more of the NFA
/// The only difference from the Plus is that the split is before the NFA.
/// </summary>
/// <param name="operandStack">The operand stack to execute the operator on</param>
public void Execute(Stack<NFAFragment> operandStack)
{
//Pop the needed NFA from the stack
NFAFragment nfa1 = operandStack.Pop();
//Create the split state
NFASplitState splitState = new NFASplitState(nfa1.startState, null);
//Make the split state the beginning of the NFA
nfa1.startState = splitState;
//Connect the exits from the NFA with the split state
nfa1.ConnectUnboundStates(splitState);
//The only unbound state now is the split state
nfa1.unboundStates.Clear();
nfa1.unboundStates.Add(splitState);
//Push the resultant NFA back
operandStack.Push(nfa1);
}
/// <summary>
/// Executes the "+" operator by creating an NFA that consists of the original NFA, the outputs from which
// go to a split state which gives an option of going back to the same NFA.
// Result - accepts one or more of the given NFA.
/// </summary>
/// <param name="operandStack">The operand stack to execute the operator on</param>
public void Execute(Stack<NFAFragment> operandStack)
{
//Get the needed NFA fragment
NFAFragment nfa1 = operandStack.Pop();
//Create the split state, with the possibility to return to the original NFA
NFASplitState splitState = new NFASplitState(nfa1.startState, null);
//Connect all exits in the original NFA to the created state
nfa1.ConnectUnboundStates(splitState);
//The only unbound state now is the split state
nfa1.unboundStates.Clear();
nfa1.unboundStates.Add(splitState);
//Push the resultant NFA back
operandStack.Push(nfa1);
}