static Set <int> AcceptStates(
ICollection <Set <int> > states,
NfaToDfaRenamer renamer,
Set <int> acceptStates)
{
Set <int> result = new Set <int>();
foreach (Set <int> dfaSubsetState in states)
{
if (acceptStates.Any(finalState => dfaSubsetState.Contains(finalState)))
{
result.Add(renamer.ToDfaStateIndex(dfaSubsetState));
}
}
return(result);
}
// Using a renamer (a Map from Set of int to int), replace
// composite (Set of int) states with simple (int) states in
// the transition relation trans, which is assumed to be a Map
// from Set of int to Map from string to Set of int. The
// result is a Map from int to Map from string to int.
// Given a Map from Set of int to Map from string to Set of
// int, use the result of MkRenamer to replace all Sets of ints
// by ints.
static IDictionary <int, Dictionary <TAlphabet, int> > Rename(
NfaToDfaRenamer renamer,
IDictionary <Set <int>, Dictionary <TAlphabet, Set <int> > > dfaTrans)
{
var newDfaTrans = new SortedDictionary <int, Dictionary <TAlphabet, int> >(); // keys/states are sorted
foreach (KeyValuePair <Set <int>, Dictionary <TAlphabet, Set <int> > > entry
in dfaTrans)
{
Set <int> dfaState = entry.Key;
var newDfaTransRow = new Dictionary <TAlphabet, int>();
foreach (KeyValuePair <TAlphabet, Set <int> > tr in entry.Value)
{
newDfaTransRow.Add(tr.Key, renamer.ToDfaStateIndex(tr.Value));
}
newDfaTrans.Add(renamer.ToDfaStateIndex(dfaState), newDfaTransRow);
}
return(newDfaTrans);
}
/// <summary>
/// McNaughton-Yamada-Thompson algorithm (aka Thompson's construction)
/// </summary>
public Dfa <TAlphabet> ToDfa(bool skipRenaming = false)
{
IDictionary <Set <int>, Dictionary <TAlphabet, Set <int> > >
cDfaTrans = CompositeDfaTrans(Start, Trans);
Set <int> cDfaStart = EpsilonClose(new Set <int>(new [] { Start }), Trans);
ICollection <Set <int> > cDfaStates = cDfaTrans.Keys;
var renamer = new NfaToDfaRenamer(cDfaStates, skipRenaming, _predicate);
// DFA-transitions (delta)
IDictionary <int, Dictionary <TAlphabet, int> > dfaTrans =
Rename(renamer, cDfaTrans);
// The singleton start state = q_0
int dfaStartStateIndex = renamer.ToDfaStateIndex(cDfaStart);
// The subset of accepting states = F
Set <int> dfaAcceptingStateIndices = AcceptStates(cDfaStates, renamer, AcceptingStates);
return(new Dfa <TAlphabet>(dfaStartStateIndex, dfaAcceptingStateIndices, dfaTrans, renamer));
}