private CharacterClass ParseeCClass()
{
//Throw away [ token
if (_ts.NextToken().Type != TokenType.OPENCLASS)
throw new ParseException("Expected [");
var cClass = new CharacterClass();
while (_ts.Peek().Type != TokenType.CLOSECLASS)
{
cClass.Elements.Add(ParseCClassElement());
}
//throw away ]
_ts.NextToken();
return cClass;
}
public NFAGraph ToDFA()
{
//first, we need to know the alphabet
var alphabet = new SortedSet<char>();
foreach (var state in _adjList.Keys)
{
foreach (var link in _adjList[state].Where(l => !l.IsEmpty))
{
alphabet.UnionWith(link.CharClass.CharSet());
}
}
var dfa = new NFAGraph();
var stateSetMap = new Dictionary<HashSet<NFAState>, NFAState>(HashSet<NFAState>.CreateSetComparer());
var startStateSet = eClosure(_startState);
dfa._startState = dfa.NewState();
stateSetMap[startStateSet] = dfa._startState;
//Follow the links of the start state
var markedDFAStates = new HashSet<HashSet<NFAState>>(HashSet<NFAState>.CreateSetComparer());
//Start at the start and continue whilst there are no unmarked states
var DFAStateQueue = new Queue<HashSet<NFAState>>();
DFAStateQueue.Enqueue(startStateSet);
while (DFAStateQueue.Count > 0)
{
var thisstate = DFAStateQueue.Dequeue();
var origdfastate = stateSetMap[thisstate];
markedDFAStates.Add(thisstate);
foreach (var c in alphabet)
{
var cclass = new CharacterClass();
cclass.Elements.Add(new CharacterClassElement(c));
cclass.IsNegated = false;
var targetStates = new HashSet<NFAState>();
foreach (var nfastate in thisstate)
{
foreach (var link in _adjList[nfastate])
{
if (CanFollowLink(link, c))
{
targetStates.Add(link.Target);
}
}
}
var targetStateClosure = eClosure(targetStates);
NFAState ndfastate;
if (!markedDFAStates.Contains(targetStateClosure))
{
DFAStateQueue.Enqueue(targetStateClosure);
ndfastate = dfa.NewState();
stateSetMap[targetStateClosure] = ndfastate;
if (targetStateClosure.Any(s => _finishState.Contains(s)))
dfa._finishState.Add(ndfastate);
}
else
{
ndfastate = stateSetMap[targetStateClosure];
}
dfa._adjList[origdfastate].Add(new NFALink()
{
IsEmpty = false,
CharClass = cclass,
Target = ndfastate
});
}
//now check for . transitions
}
return dfa;
}
public NFAGraph(CharacterClass CClass)
{
InstantiateFromCharClass(CClass);
}
private void InstantiateFromSingleChar(SingleChar C)
{
var CClass = new CharacterClass();
CClass.Elements.Add(new CharacterClassElement(C.Character));
InstantiateFromCharClass(CClass);
}
private void InstantiateFromCharClass(CharacterClass CClass)
{
_startState = NewState();
_finishState.Add(NewState());
var link = new NFALink();
link.CharClass = CClass;
link.Target = _finishState.Single();
_adjList[_startState].Add(link);
}
