@Override public CyclicStackItem<P> enter(Pda<S, P> pda, S state, CyclicStackItem<P> previous) { P item; if ((item = pda.getPush(state)) != null) return previous.push(item); if ((item = pda.getPop(state)) != null) return previous.pop(item); if (previous == null) return new CyclicStackItem<P>(); return previous; }
public <S, P, R, D extends Pda<S, P>> D filterEdges( Pda<S, P> pda, Traverser<? super Pda<S, P>, S, R> traverser, PdaFactory<D, S, P, S> factory) { HashStack<TraversalItem<S, R>> trace = new HashStack<TraversalItem<S, R>>(); R previous = traverser.enter(pda, pda.getStart(), null); if (previous == null) return factory == null ? null : factory.create(pda.getStart(), pda.getStop()); Map<S, Integer> distances = new NfaUtil().distanceToFinalStateMap(pda); MappedComparator<S, Integer> distanceComp = new MappedComparator<S, Integer>(distances); trace.push(newItem(pda, distanceComp, distances, pda.getStart(), previous)); Multimap<S, S> edges = LinkedHashMultimap.create(); HashSet<S> states = Sets.newLinkedHashSet(); HashSet<Pair<S, R>> success = Sets.newLinkedHashSet(); states.add(pda.getStart()); states.add(pda.getStop()); ROOT: while (!trace.isEmpty()) { TraversalItem<S, R> current = trace.peek(); while (current.followers.hasNext()) { S next = current.followers.next(); R item = traverser.enter(pda, next, current.data); if (item != null) { if ((next == pda.getStop() && traverser.isSolution(item)) || success.contains(Tuples.create(next, item))) { S s = null; for (TraversalItem<S, R> i : trace) { if (s != null) edges.put(s, i.state); states.add(i.state); success.add(Tuples.create(i.state, i.data)); s = i.state; } edges.put(s, next); } else { if (trace.push(newItem(pda, distanceComp, distances, next, item))) continue ROOT; } } } trace.pop(); } if (factory == null) return null; D result = factory.create(pda.getStart(), pda.getStop()); Map<S, S> old2new = Maps.newLinkedHashMap(); old2new.put(pda.getStart(), result.getStart()); old2new.put(pda.getStop(), result.getStop()); for (S old : states) { if (old == pda.getStart() || old == pda.getStop()) continue; else if (pda.getPop(old) != null) old2new.put(old, factory.createPop(result, old)); else if (pda.getPush(old) != null) old2new.put(old, factory.createPush(result, old)); else old2new.put(old, factory.createState(result, old)); } for (S old : states) { List<S> followers = Lists.newArrayList(); for (S f : edges.get(old)) followers.add(old2new.get(f)); factory.setFollowers(result, old2new.get(old), followers); } return result; }
protected <S, P> TraceItem<S, P> traceToWithPruningStack( Pda<S, P> pda, Iterable<S> starts, Iterator<P> stack, Predicate<S> matches, Predicate<S> canPass) { StackItem<P> stackItem = createStack(stack); List<TraceItem<S, P>> current = Lists.newArrayList(); Set<S> visited = Sets.newLinkedHashSet(starts); TraceItem<S, P> result = null; for (S start : starts) { TraceItem<S, P> item = new TraceItem<S, P>(null, start, stackItem); // if (matches.apply(start)) // result = item; current.add(item); } int counter = stackItem.size() * -1; while (current.size() > 0 && counter < visited.size()) { List<TraceItem<S, P>> newCurrent = Lists.newArrayList(); for (TraceItem<S, P> trace : current) for (S follower : pda.getFollowers(trace.state)) { if (matches.apply(follower)) { TraceItem<S, P> found = new TraceItem<S, P>(trace, follower, trace.stackitem); if (found.stackitem == null) return found; if (result == null || result.stackitem.size() > found.stackitem.size()) { result = found; counter = result.stackitem.size() * -1; } else if (result.stackitem.size() == found.stackitem.size() && result.size() > found.size()) { result = found; counter = result.stackitem.size() * -1; } } if (canPass.apply(follower)) { P push = pda.getPush(follower); visited.add(follower); if (push != null) { StackItem<P> pushed = trace.stackitem.push(push); newCurrent.add(new TraceItem<S, P>(trace, follower, pushed)); } else { P pop = pda.getPop(follower); if (pop != null) { if (trace.stackitem != null && pop == trace.stackitem.peek()) { StackItem<P> popped = trace.stackitem.pop(); newCurrent.add(new TraceItem<S, P>(trace, follower, popped)); } } else newCurrent.add(new TraceItem<S, P>(trace, follower, trace.stackitem)); } } } current = newCurrent; counter++; } return result; }
protected <S, P, T, D extends Pda<S, P>> S clone( S state, Pda<S, P> src, D target, Function<S, T> tokens, PdaFactory<D, S, P, T> fact, Identity<S> identity) { if (state == src.getStart()) return target.getStart(); if (state == src.getStop()) return target.getStop(); P push = src.getPush(state); if (push != null) return identity.get(fact.createPush(target, tokens.apply(state))); P pop = src.getPop(state); if (pop != null) return identity.get(fact.createPop(target, tokens.apply(state))); return identity.get(fact.createState(target, tokens.apply(state))); }
public <S, P, D extends Pda<S, P>> Map<P, Pair<S, S>> collectPopsAndPushs(Pda<S, P> pda) { Map<P, Pair<S, S>> result = Maps.newLinkedHashMap(); for (S s : nfaUtil.collect(pda)) { P push = pda.getPush(s); if (push != null) { Pair<S, S> o = result.get(push); Pair<S, S> n = Tuples.create(s, o == null ? null : o.getSecond()); result.put(push, n); } P pop = pda.getPop(s); if (pop != null) { Pair<S, S> o = result.get(pop); Pair<S, S> n = Tuples.create(o == null ? null : o.getFirst(), s); result.put(pop, n); } } return result; }
@Override public boolean apply(S input) { return pda.getPop(input) != null; }