/// <summary>
/// Adds a transition to the specified state, on the specified character.
/// </summary>
/// <param name="character">The character on which to transition</param>
/// <param name="destState">The destination state to which this state transitions</param>
/// <returns>True if this transition could be added (the character is in the parent
/// DFA's alphabet, and a transition for this character did not exist, else False.</returns>
public bool AddTransition(char character, DFA_State destState)
{
if (false == this.Parent.Alphabet.Contains(character))
{
return(false);
}
if (this.Transitions.ContainsKey(character))
{
return(false);
}
this.Transitions.Add(character, destState);
return(true);
}
/// <summary>
/// Steps on the specified character and determines whether this is a valid
/// transition
/// </summary>
/// <param name="character">The character on which to transition</param>
/// <returns>Whether this step was valid</returns>
public bool StepOn(char character)
{
DFA_State nextState = this.CurrentState.TransitionOn(character);
this.CurrentState = nextState;
if (null == this.CurrentState)
{
return(false);
}
else
{
return(true);
}
}
/// <summary>
/// Parses the accept states from the given string
/// </summary>
/// <param name="accept_string"></param>
private void _parseAcceptStates(string accept_string)
{
StringBuilder sb = new StringBuilder();
HashSet <DFA_State> acceptStates = new HashSet <DFA_State>();
foreach (char c in accept_string)
{
if (c == ',')
{
DFA_State newAccept = this.getStateBy(sb.ToString());
if (false == acceptStates.Add(newAccept))
{
throw new ArgumentException("Illegal accept state string");
}
}
else
{
sb.Append(c);
}
}
this.AcceptStates = acceptStates;
}
/// <summary>
/// Parses the transitions from the given string
/// </summary>
/// <param name="transition_string"></param>
private void _parseTransitions(string transition_string)
{
StringBuilder sb = new StringBuilder();
DFA_State workingOnState = null;
DFA_State transDest = null;
char transChar = Char.MinValue;
char prevChar = Char.MinValue;
foreach (char c in transition_string)
{
if (c == ':')
{
workingOnState = this.getStateBy(sb.ToString());
if (workingOnState == null)
{
throw new ArgumentException("Specified transition for nonexistent state");
}
sb.Clear();
}
else if (c == ',')
{
if (prevChar == Char.MinValue)
{
throw new ArgumentException("Illegal transition string");
}
transChar = prevChar;
sb.Clear();
}
else if (c == ';')
{
transDest = this.getStateBy(sb.ToString());
if ((null == workingOnState) ||
(null == transDest) ||
(char.MinValue == prevChar))
{
throw new ArgumentException("Illegal transition string");
}
workingOnState.AddTransition(transChar, transDest);
sb.Clear();
}
else if (c == '.')
{
transDest = this.getStateBy(sb.ToString());
if ((null == workingOnState) ||
(null == transDest) ||
(char.MinValue == prevChar))
{
throw new ArgumentException("Illegal transition string");
}
workingOnState.AddTransition(transChar, transDest);
workingOnState = null;
sb.Clear();
}
else
{
sb.Append(c);
}
prevChar = c;
}
}
