package edu.berkeley.sbp;
import edu.berkeley.sbp.*;
import edu.berkeley.sbp.util.*;
-import edu.berkeley.sbp.*;
import edu.berkeley.sbp.Sequence.Position;
-import edu.berkeley.sbp.*;
import java.io.*;
import java.util.*;
-import java.lang.reflect.*;
/** a parser which translates streams of Tokens of type T into a Forest<R> */
public abstract class Parser<T extends Token, R> {
- public final Table pt;
+ private final Table pt;
/** 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; }
+ /** implement this method to create the output forest corresponding to a lone shifted input token */
public abstract Forest<R> shiftedToken(T t, Token.Location loc);
- public abstract Topology<T> top();
-
- /** 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 {
- Forest<R> ret = parse(input);
- try { return ret.expand1(); }
- catch (Ambiguous a) {
- System.out.println("while expanding:");
- System.out.println(ret);
- throw a;
- }
- }
+ /** this method must return an empty topology of the input token type */
+ public abstract Topology<T> top();
/** 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 {
+ public Forest<R> parse(Token.Stream<T> input) throws IOException, ParseFailed {
GSS gss = new GSS();
Token.Location loc = input.getLocation();
GSS.Phase current = gss.new Phase(null, this, null, input.next(1, 0, 0), loc, null);
int count = 1;
for(;;) {
loc = input.getLocation();
- //current.checkFailure();
current.reduce();
Forest forest = current.token==null ? null : shiftedToken((T)current.token, loc);
GSS.Phase next = gss.new Phase(current, this, current, input.next(count, gss.resets, gss.waits), loc, forest);
current = next;
}
}
-
-
- // Exceptions //////////////////////////////////////////////////////////////////////////////
-
- public static class Failed extends RuntimeException {
- private final Token.Location location;
- private final String message;
- 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))*/; }
- }
-
- public static class Ambiguous extends RuntimeException {
- public final Forest ambiguity;
- public Ambiguous(Forest ambiguity) { this.ambiguity = ambiguity; }
- public String toString() {
- StringBuffer sb = new StringBuffer();
- sb.append("unresolved ambiguity "/*"at " + ambiguity.getLocation() + ":"*/);
- for(Object result : ambiguity.expand(false))
- sb.append("\n " + result);
- return sb.toString();
- }
- }
-
// Table //////////////////////////////////////////////////////////////////////////////
public final Walk.Cache cache = this;
- public HashMapBag<Position,State> byPosition = new HashMapBag<Position,State>();
-
private void walk(Element e, HashSet<Element> hs) {
if (e==null) return;
if (hs.contains(e)) return;
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());
+ cache.ys.addAll(e, new Walk.YieldSet(e, cache).walk());
HashSet<Position> hp = new HashSet<Position>();
reachable(start0, hp);
this.start = new State(hp, all_states, all_elements);
if (start0.contains(p.owner()) && p.next()==null)
state.accept = true;
- if (p.isRightNullable(cache)) {
+ if (isRightNullable(p)) {
Walk.Follow wf = new Walk.Follow(top.empty(), p.owner(), all_elements, cache);
Reduction red = new Reduction(p);
}
}
+ private boolean isRightNullable(Position p) {
+ if (p.isLast()) return true;
+ if (!p.element().possiblyEpsilon(this)) return false;
+ return isRightNullable(p.next());
+ }
+
/** a single state in the LR table and the transitions possible from it */
public class State implements Comparable<Table.State>, IntegerMappable, Iterable<Position> {
// register ourselves in the all_states hash so that no
// two states are ever created with an identical position set
all_states.put(hs, this);
- for(Position p : hs) byPosition.add(p,this);
// Step 1a: examine all Position's in this state and compute the mappings from
// sets of follow tokens (tokens which could follow this position) to sets
// "yields" [in one or more step] is used instead of "produces" [in exactly one step]
// to avoid having to iteratively construct our set of States as shown in most
// expositions of the algorithm (ie "keep doing XYZ until things stop changing").
- /*
- for(Element e : all_elements) {
- if (e instanceof Atom) continue;
- HashSet<Position> h = new Walk.Closure(null, g.cache).closure(e, hs);
- State s = all_states.get(h) == null ? new State(h, all_states, all_elements) : all_states.get(h);
- if (gotoSetNonTerminals.get(e) != null)
- throw new Error("this should not happen");
- gotoSetNonTerminals.put(e, s);
- }
- */
HashMapBag<Element,Position> move = new HashMapBag<Element,Position>();
for(Position p : hs) {
Element e = p.element();
if (e==null) continue;
- HashSet<Element> ys = cache.ys.get(e);
- if (ys != null) {
- for(Element y : ys) {
- HashSet<Position> hp = new HashSet<Position>();
- reachable(p.next(), hp);
- move.addAll(y, hp);
- }
+ for(Element y : cache.ys.getAll(e)) {
+ HashSet<Position> hp = new HashSet<Position>();
+ reachable(p.next(), hp);
+ move.addAll(y, hp);
}
}
for(Element y : move) {
projects / sbp.git / blobdiff