private final Table pt;
- /**
- * create a parser to parse the grammar with start symbol <tt>u</tt>
- */
+ /** create a parser to parse the grammar with start symbol <tt>u</tt> */
protected Parser(Union u) { this.pt = new Table(u, top()); }
protected Parser(Table pt) { this.pt = pt; }
/** parse <tt>input</tt> for a exactly one unique result, throwing <tt>Ambiguous</tt> if not unique or <tt>Failed</tt> if none */
- public Tree<R> parse1(Token.Stream<T> input) throws IOException, Failed, Ambiguous { return parse(input).expand1(); }
+ public Tree<R> parse1(Token.Stream<T> input) throws IOException, Failed, Ambiguous {
+ Forest<R> ret = parse(input);
+ try { return ret.expand1(); }
+ catch (Ambiguous a) {
+ System.out.println("while expanding:");
+ System.out.println(ret);
+ throw a;
+ }
+ }
/** parse <tt>input</tt>, using the table <tt>pt</tt> to drive the parser */
public Forest<R> parse(Token.Stream<T> input) throws IOException, Failed {
// Table //////////////////////////////////////////////////////////////////////////////
/** an SLR(1) parse table which may contain conflicts */
- static class Table {
+ static class Table extends Walk.Cache {
- private final Union start0 = new Union("0");
- private final Sequence start0seq;
-
- public final Walk.Cache cache = new Walk.Cache();
-
- public HashSet<Position> closure() {
- HashSet<Position> hp = new HashSet<Position>();
- reachable(start0, hp);
- return hp;
- }
+ public final Walk.Cache cache = this;
private void walk(Element e, HashSet<Element> hs) {
if (e==null) return;
walk(p.element(), hs);
}
}
- public HashSet<Element> walk() {
- HashSet<Element> ret = new HashSet<Element>();
- walk(start0, ret);
- return ret;
- }
-
- /*
- public String toString() {
- StringBuffer sb = new StringBuffer();
- for(Element e : walk())
- if (e instanceof Union)
- ((Union)e).toString(sb);
- return sb.toString();
- }
- */
/** the start state */
public final State start;
/** construct a parse table for the given grammar */
public Table(Topology top) { this("s", top); }
public Table(String startSymbol, Topology top) { this(new Union(startSymbol), top); }
- public Table(Union u, Topology top) {
+ public Table(Union ux, Topology top) {
+ Union start0 = new Union("0");
+ start0.add(new Sequence.Singleton(ux, null, null));
+
+ for(Sequence s : start0) cache.eof.put(s, true);
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);
+ HashSet<Element> all_elements = new HashSet<Element>();
+ walk(start0, all_elements);
for(Element e : all_elements)
cache.ys.put(e, new Walk.YieldSet(e, cache).walk());
- this.start = new State(closure(), all_states, all_elements);
+ HashSet<Position> hp = new HashSet<Position>();
+ reachable(start0, hp);
+ this.start = new State(hp, all_states, all_elements);
// for each state, fill in the corresponding "row" of the parse table
for(State state : all_states.values())
for(Position p : state.hs) {
// the Grammar's designated "last position" is the only accepting state
- if (p==start0seq.firstp().next())
+ if (start0.contains(p.owner()) && p.next()==null)
state.accept = true;
// FIXME: how does right-nullability interact with follow restrictions?
Walk.Follow wf = new Walk.Follow(top.empty(), p.owner(), all_elements, cache);
Reduction red = new Reduction(p);
state.reductions.put(wf.walk(p.owner()), red);
- if (wf.includesEof()) state.eofReductions.add(red, true);
+ if (wf.includesEof()) state.eofReductions.add(red);
}
// if the element following this position is an atom, copy the corresponding
/** a single state in the LR table and the transitions possible from it */
public class State implements Comparable<Table.State>, Iterable<Position> {
- public final int idx = master_state_idx++;
+ /*
+ public boolean isResolvable(Token t) {
+ boolean found = false;
+ for(Reduction r : getReductions(t)) {
+ Position p = r.position;
+ if (!p.isRightNullable(cache)) continue;
+ if (p.owner().firstp()==p) continue;
+ if (found) {
+ // found two items meeting criteria #1
+ return false;
+ } else {
+ found = true;
+ continue;
+ }
+ if (p.element()==null) continue;
+ Topology first = new Walk.First(top(), cache).walk(p.element());
+ if (first.contains(t))
+ }
+ }
+ */
+
+ public final int idx = master_state_idx++;
private final HashSet<Position> hs;
private transient HashMap<Element,State> gotoSetNonTerminals = new HashMap<Element,State>();
private transient TopologicalBag<Token,State> gotoSetTerminals = new TopologicalBag<Token,State>();
private TopologicalBag<Token,Reduction> reductions = new TopologicalBag<Token,Reduction>();
- private FastSet<Reduction> eofReductions = new FastSet<Reduction>();
+ private HashSet<Reduction> eofReductions = new HashSet<Reduction>();
private TopologicalBag<Token,State> shifts = new TopologicalBag<Token,State>();
private boolean accept = false;
public class Reduction {
// FIXME: cleanup; almost everything in here could go in either Sequence.Position.getRewrite() or else in GSS.Reduct
public final int numPop;
- private final Position position;
+ /*private*/ final Position position;
private final Forest[] holder; // to avoid constant reallocation
public int hashCode() { return position.hashCode(); }
public boolean equals(Object o) {
holder[numPop-1] = f;
return reduce(parent, numPop-2, rex, onlychild, target);
}
- public Forest reduce(GSS.Phase.Node parent, GSS.Phase.Node onlychild, GSS.Phase target, Forest rex) {
- return reduce(parent, numPop-1, rex, onlychild, target);
+ public Forest reduce(GSS.Phase.Node parent, GSS.Phase.Node onlychild, Forest rex) {
+ return reduce(parent, numPop-1, rex, onlychild, parent.phase());
+ }
+
+ private Forest zero = null;
+ public Forest zero() {
+ if (zero != null) return zero;
+ if (numPop > 0) throw new Error();
+ return zero = position.rewrite(null);
}
// FIXME: this could be more elegant and/or cleaner and/or somewhere else
} else {
State state = parent.state.gotoSetNonTerminals.get(position.owner());
if (state!=null)
- target.newNode(parent, rex, state, numPop<=0, parent.phase);
+ target.newNode(parent, rex, state, numPop<=0, parent.phase());
}
return rex;
}
projects / sbp.git / blobdiff