public static Automaton Union(IList <Automaton> automatons)
{
var ids = new HashSet <int>();
foreach (var a in automatons)
{
_ = ids.Add(RuntimeHelpers.GetHashCode(a));
}
var hasAliases = ids.Count != automatons.Count;
var s = new State();
foreach (var b in automatons)
{
if (b.IsEmpty)
{
continue;
}
var bb = b;
bb = hasAliases ? bb.CloneExpanded() : bb.CloneExpandedIfRequired();
s.AddEpsilon(bb.Initial);
}
var automaton = new Automaton
{
Initial = s,
IsDeterministic = false,
};
automaton.ClearHashCode();
automaton.CheckMinimizeAlways();
return(automaton);
}
public static Automaton Optional(Automaton a)
{
a = a.CloneExpandedIfRequired();
var s = new State();
s.AddEpsilon(a.Initial);
s.Accept = true;
a.Initial = s;
a.IsDeterministic = false;
a.ClearHashCode();
a.CheckMinimizeAlways();
return(a);
}
public static Automaton Repeat(Automaton a)
{
a = a.CloneExpanded();
var s = new State
{
Accept = true,
};
s.AddEpsilon(a.Initial);
foreach (var p in a.GetAcceptStates())
{
p.AddEpsilon(s);
}
a.Initial = s;
a.IsDeterministic = false;
a.ClearHashCode();
a.CheckMinimizeAlways();
return(a);
}
public static Automaton Concatenate(Automaton a1, Automaton a2)
{
if (a1.IsSingleton && a2.IsSingleton)
{
return(BasicAutomata.MakeString(a1.Singleton + a2.Singleton));
}
if (IsEmpty(a1) || IsEmpty(a2))
{
return(BasicAutomata.MakeEmpty());
}
var deterministic = a1.IsSingleton && a2.IsDeterministic;
if (a1 == a2)
{
a1 = a1.CloneExpanded();
a2 = a2.CloneExpanded();
}
else
{
a1 = a1.CloneExpandedIfRequired();
a2 = a2.CloneExpandedIfRequired();
}
foreach (var s in a1.GetAcceptStates())
{
s.Accept = false;
s.AddEpsilon(a2.Initial);
}
a1.IsDeterministic = deterministic;
a1.ClearHashCode();
a1.CheckMinimizeAlways();
return(a1);
}
public static void AddEpsilons(Automaton a, ICollection <StatePair> pairs)
{
a.ExpandSingleton();
var forward = new Dictionary <State, HashSet <State> >();
var back = new Dictionary <State, HashSet <State> >();
foreach (var p in pairs)
{
var to = forward[p.FirstState];
if (to == null)
{
to = new HashSet <State>();
forward.Add(p.FirstState, to);
}
_ = to.Add(p.SecondState);
var from = back[p.SecondState];
if (from == null)
{
from = new HashSet <State>();
back.Add(p.SecondState, from);
}
_ = from.Add(p.FirstState);
}
var worklist = new LinkedList <StatePair>(pairs);
var workset = new HashSet <StatePair>(pairs);
while (worklist.Count != 0)
{
var p = worklist.RemoveAndReturnFirst();
_ = workset.Remove(p);
var to = forward[p.SecondState];
var from = back[p.FirstState];
if (to != null)
{
foreach (var s in to)
{
var pp = new StatePair(p.FirstState, s);
if (!pairs.Contains(pp))
{
pairs.Add(pp);
_ = forward[p.FirstState].Add(s);
_ = back[s].Add(p.FirstState);
_ = worklist.AddLast(pp);
_ = workset.Add(pp);
if (from != null)
{
foreach (var q in from)
{
var qq = new StatePair(q, p.FirstState);
if (!workset.Contains(qq))
{
_ = worklist.AddLast(qq);
_ = workset.Add(qq);
}
}
}
}
}
}
}
foreach (var p in pairs)
{
p.FirstState.AddEpsilon(p.SecondState);
}
a.IsDeterministic = false;
a.ClearHashCode();
a.CheckMinimizeAlways();
}
