public static SmartSet <State> GetClosure(IEnumerable <State> states, Automaton automaton)
{
var list = new List <State>();
foreach (var state in states)
{
list.Add(state);
}
for (var i = 0; i < list.Count; i++)
{
var state = list[i];
var transitions = automaton.SuccessorEdges(state);
foreach (var transition in transitions)
{
if (Automaton.IsEpsilonTransition(transition))
{
var toState = transition.To;
if (list.Contains(toState))
{
continue;
}
list.Add(toState);
}
}
}
var result = new SmartSet <State>();
result.UnionWith(list);
return(result);
}
public State AddHashSetState(Automaton dfa, SmartSet <State> states)
{
var result = FindHashSetState(dfa, states);
if (result != null)
{
return(result);
}
result = new State(dfa);
_hash_sets.Add(states, result);
return(result);
}
/* Apply powerset construction to the NFA to convert to a DFA.
* Note, the result of this method isn't strictly a DFA because
* edges in the automaton can be text or code, which function just like
* epsilon transitions--no input is consumed for the edge.
*/
public Automaton Optimize(Automaton nfa)
{
var dfa = new Automaton();
// For every state s, compute collection of states along epsilon edges
// to get an initial computation of dfa states.
foreach (var s in nfa.Vertices)
{
var c = ClosureTaker.GetClosure(new List <State> {
s
}, nfa);
_closure[s] = c;
}
// For every state set, compute sums and fix up state sets.
foreach (var p in _closure)
{
var key = p.Key;
var set = p.Value;
foreach (var s in set)
{
_closure[s].UnionWith(set);
}
}
// For every state in nfa using Tarjan walk,
// sum sets with common transitions.
var ordered_list = new TarjanNoBackEdges <State, Edge>(nfa).ToList();
ordered_list.Reverse();
var changed = true;
while (changed)
{
changed = false;
foreach (var s in ordered_list)
{
var closure = _closure[s];
var transitions = ClosureTaker.GatherTransitions(closure);
foreach (var transition_set in transitions)
{
var key = transition_set.Key;
var value = transition_set.Value;
var state_set = new SmartSet <State>();
// All states in value must have common set in dfa.
foreach (var e in value)
{
var c = e.To;
var cl = _closure[c];
state_set.UnionWith(cl);
}
foreach (var c in state_set)
{
if (!_closure[c].Equals(state_set))
{
_closure[c] = state_set;
changed = true;
}
}
}
}
}
var initialState = CreateInitialState(nfa, dfa);
foreach (var p in _closure)
{
var state_set = p.Value;
var new_dfa_state = FindHashSetState(dfa, state_set);
if (new_dfa_state == null)
{
var state = AddHashSetState(dfa, state_set);
{
var mark = false;
foreach (var s in state_set)
{
if (nfa.FinalStates.Contains(s))
{
mark = true;
}
}
if (mark && !dfa.FinalStates.Contains(state))
{
dfa.AddFinalState(state);
}
}
}
}
//System.Console.Error.WriteLine(dfa.ToString());
foreach (var p in _closure)
{
var k = p.Key;
var state_set = p.Value;
var dfa_state = FindHashSetState(dfa, state_set);
// System.Console.Error.WriteLine("State " + dfa_state.Id + ":"
// + state_set.Aggregate(
// "", // start with empty string to handle empty list case.
// (current, next) => current + ", " + next));
}
//System.Console.Error.WriteLine(dfa.ToString());
foreach (var from_dfa_state in dfa.Vertices)
{
var nfa_state_set = FindHashSet(from_dfa_state);
var transitions = ClosureTaker.GatherTransitions(nfa_state_set);
foreach (var transition_set in transitions)
{
// Note, transitions is a collection of edges for a given string.
// For the NFA, an edge has one Ast for the edge because it came from one pattern.
// But, for the DFA, there could be multiple edges for the same string,
// each from a different pattern! Compute the set of Asts for
// all edges.
var key = transition_set.Key;
var value = transition_set.Value;
var state_set = new HashSet <State>();
foreach (var e in value)
{
state_set.Add(e.To);
}
// Find in all previous states.
var new_state_set = _hash_sets.Where(hs => state_set.IsSubsetOf(hs.Key)).FirstOrDefault().Key;
if (new_state_set == null)
{
new_state_set = _closure[state_set.First()];
}
var to_dfa_state = FindHashSetState(dfa, new_state_set);
var mods = value.First().EdgeModifiers;
var asts = new List <IParseTree>();
foreach (var v in value)
{
foreach (var v2 in v.AstList)
{
asts.Add(v2);
}
}
var he = new Edge(dfa, from_dfa_state, to_dfa_state, asts, mods);
}
}
// Add in "any" fragment in order to match tree nodes that aren't in pattern.
//{
// State s3 = new State(dfa); s3.Commit();
// var e1 = new Edge(dfa, s3, s3, null, Edge.EmptyAst, (int)Edge.EdgeModifiers.Any); e1.Commit();
// var f = new Fragment(s3);
//}
return(dfa);
}
public State FindHashSetState(Automaton dfa, SmartSet <State> states)
{
_hash_sets.TryGetValue(states, out State result);
return(result);
}