private final Table pt;
- private static void reachable(Element e, HashSet<Position> h) {
- if (e instanceof Atom) return;
- for(Sequence s : ((Union)e))
- reachable(s.firstp(), h);
- }
- private static void reachable(Position p, HashSet<Position> h) {
- if (h.contains(p)) return;
- h.add(p);
- if (p.element() != null) reachable(p.element(), h);
- }
-
/**
* create a parser to parse the grammar with start symbol <tt>u</tt>
*/
// Table //////////////////////////////////////////////////////////////////////////////
- static class Top extends Union { public Top() { super("0"); } }
-
/** an SLR(1) parse table which may contain conflicts */
static class Table {
- private final Union start0 = new Top();
+ private final Union start0 = new Union("0");
private final Sequence start0seq;
public final Walk.Cache cache = new Walk.Cache();
reachable(start0, hp);
return hp;
}
- public Position firstPosition() { return start0seq.firstp(); }
- public Position lastPosition() { Position ret = start0seq.firstp(); while(!ret.isLast()) ret = ret.next(); return ret; }
private void walk(Element e, HashSet<Element> hs) {
if (e==null) return;
public Table(Topology top) { this("s", top); }
public Table(String startSymbol, Topology top) { this(new Union(startSymbol), top); }
public Table(Union u, Topology top) {
+ cache.eof.put(start0, true);
start0seq = new Sequence.Singleton(u, null, null);
+ cache.eof.put(start0seq, true);
start0.add(start0seq);
// construct the set of states
HashMap<HashSet<Position>,State> all_states = new HashMap<HashSet<Position>,State>();
HashSet<Element> all_elements = walk();
+ all_elements.add(start0);
+ all_elements.add(start0seq);
for(Element e : all_elements)
cache.ys.put(e, new Walk.YieldSet(e, cache).walk());
this.start = new State(closure(), all_states, all_elements);
for(Position p : state.hs) {
// the Grammar's designated "last position" is the only accepting state
- if (p==lastPosition())
+ if (p==start0seq.firstp().next())
state.accept = true;
// FIXME: how does right-nullability interact with follow restrictions?
Atom a = (Atom)position.element();
HashSet<Position> hp = new HashSet<Position>();
reachable(position.next(), hp);
- bag0.addAll(a, /*clo.walk()*/hp);
+ bag0.addAll(a, hp);
}
// Step 1b: for each _minimal, contiguous_ set of characters having an identical next-position
}
private static final Forest[] emptyForestArray = new Forest[0];
+
+
+ // Helpers //////////////////////////////////////////////////////////////////////////////
+
+ private static void reachable(Element e, HashSet<Position> h) {
+ if (e instanceof Atom) return;
+ for(Sequence s : ((Union)e))
+ reachable(s.firstp(), h);
+ }
+ private static void reachable(Position p, HashSet<Position> h) {
+ if (h.contains(p)) return;
+ h.add(p);
+ if (p.element() != null) reachable(p.element(), h);
+ }
+
}