public static IEnumerable <int> Step(this IAutomaton @this, IEnumerable <int> state, char character)
{
return(@this.GetEpsilonClosure(state.SelectMany(s => @this.TransitionsBySource
.GetOrDefault(s, EmptyTargets)
.ReadChar(character))
.ToArray()));
}
public static bool Read(this IAutomaton @this, string input)
{
@this.Print();
var state = new HashSet <int>(@this.GetEpsilonClosure(@this.StartState));
foreach (var c in input)
{
state = new HashSet <int>(@this.Step(state, c));
if (!state.Any())
{
return(false);
}
}
return(@this.AcceptingStates.Intersect(state).Any());
}
public static IAutomaton Determinize(this IAutomaton @this)
{
var builder = new AutomatonBuilder();
var newStates = new Dictionary <decimal, int>();
var start = @this.GetEpsilonClosure(@this.StartState);
var queue = new Queue <IEnumerable <int> >();
var transitions = new LinkedList <Tuple <decimal, ICharSet, decimal> >();
queue.Enqueue(start);
while (queue.Any())
{
var source = queue.Dequeue();
var sourceBits = source.ToBits();
if (newStates.ContainsKey(sourceBits))
{
continue;
}
var state = builder.AddState();
newStates[sourceBits] = state;
//define start and end
if (source == start)
{
builder.SetStartState(state);
}
if (source.Any(st => @this.AcceptingStates.Contains(st)))
{
builder.AcceptState(state);
}
//get all possible inputs
var inputs = new List <ICharSet>();
foreach (var st in source)
{
var transitionTargets = @this.TransitionsBySource.GetOrDefault(st);
if (transitionTargets == null)
{
continue;
}
foreach (var lhs in transitionTargets.GetKeys())
{
if (lhs != CharSet.Epsilon)
{
// A \ B
// B \ A
// A ^ B
var distinct = true;
inputs = inputs.SelectMany(rhs =>
{
var first = lhs.Except(rhs);
var second = rhs.Except(lhs);
var third = lhs.Intersect(rhs);
if (third.Any())
{
distinct = false;
}
return(new[] { first, second, third }.Where(a => a.Length > 0));
}).ToList();
if (distinct)
{
inputs.Add(lhs);
}
}
}
}
//find target states (in epsilon closure)
foreach (var c in inputs)
{
var dfaState = new HashSet <int>();
foreach (var st in source)
{
var transition = @this.TransitionsBySource.GetOrDefault(st);
var targets = transition?.ReadSet(c);
if (targets == null)
{
continue;
}
foreach (var target in targets)
{
dfaState.Add(target);
}
}
if (dfaState.Any())
{
var epsilonTarget = @this.GetEpsilonClosure(dfaState.ToArray());
var targetBits = epsilonTarget.ToBits();
transitions.AddLast(new Tuple <decimal, ICharSet, decimal>(sourceBits, c, targetBits));
queue.Enqueue(epsilonTarget);
}
}
}
//add all transitions
foreach (var transition in transitions)
{
var source = newStates[transition.Item1];
var target = newStates[transition.Item3];
builder.AddTransition(source, transition.Item2, target);
}
return(builder.Build());
}