import java.lang.reflect.*;
/** a parser which translates streams of Tokens of type T into a Forest<R> */
-public class Parser<T extends Token, R> {
+public abstract class Parser<T extends Token, R> {
private final Table pt;
- //public Parser( Topology top) { this(new Table( top)); }
- //public Parser(String s, Topology top) { this(new Table(s, top)); }
-
/**
* create a parser to parse the grammar with start symbol <tt>u</tt>
- * @param top a "sample" Topology<T> that can be cloned (FIXME, demanding this is lame)
*/
- public Parser(Union u, Topology<T> top) { this(new Table(u, top)); }
+ protected Parser(Union u) { this.pt = new Table(u, top()); }
+ protected Parser(Table pt) { this.pt = pt; }
+
+ public abstract Forest<R> shiftedToken(T t, Token.Location loc);
+ public abstract Topology<T> top();
- 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(); }
/** 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 {
GSS gss = new GSS();
- GSS.Phase current = gss.new Phase(null, input.next());
+ Token.Location loc = input.getLocation();
+ GSS.Phase current = gss.new Phase(null, input.next(), loc);
current.newNode(null, null, pt.start, true, null);
for(;;) {
- GSS.Phase next = gss.new Phase(current, input.next());
+ loc = input.getLocation();
+ GSS.Phase next = gss.new Phase(current, input.next(), loc);
current.reduce();
- current.shift(next);
+ Forest forest = current.token==null ? null : shiftedToken((T)current.token, loc);
+ current.shift(next, forest);
if (current.isDone()) return (Forest<R>)current.finalResult;
current.checkFailure();
current = next;
public Failed() { this("", null); }
public Failed(String message, Token.Location loc) { this.location = loc; this.message = message; }
public Token.Location getLocation() { return location; }
- public String toString() { return message + (location==null ? "" : (" at " + location + "\n" + location.getContext())); }
+ public String toString() { return message + (location==null ? "" : (" at " + location)); }
}
public static class Ambiguous extends RuntimeException {
/** 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;
- static class Top extends Union { public Top() { super("0"); } }
public final Walk.Cache cache = new Walk.Cache();
public HashSet<Position> closure() {
HashSet<Position> hp = new HashSet<Position>();
- start0.reachable(hp);
+ 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?
// all right-nullable rules get a reduction [Johnstone 2000]
if (p.isRightNullable(cache)) {
- Walk.Follow wf = new Walk.Follow(top.fresh(), p.owner(), all_elements, cache);
+ 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 the element following this position is an atom, copy the corresponding
// set of rows out of the "master" goto table and into this state's shift table
if (p.element() != null && p.element() instanceof Atom)
- state.shifts.addAll(state.gotoSetTerminals.subset(((Atom)p.element()).top()));
+ state.shifts.addAll(state.gotoSetTerminals.subset(((Atom)p.element())));
}
}
if (position.isLast() || !(position.element() instanceof Atom)) continue;
Atom a = (Atom)position.element();
HashSet<Position> hp = new HashSet<Position>();
- position.next().reachable(hp);
- bag0.addAll(a.top(), /*clo.walk()*/hp);
+ reachable(position.next(), hp);
+ bag0.addAll(a, hp);
}
// Step 1b: for each _minimal, contiguous_ set of characters having an identical next-position
if (ys != null) {
for(Element y : ys) {
HashSet<Position> hp = new HashSet<Position>();
- p.next().reachable(hp);
+ reachable(p.next(), hp);
move.addAll(y, hp);
}
}
}
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);
+ }
+
}
projects / sbp.git / blobdiff