checkpoint

[sbp.git] / src / edu / berkeley / sbp / Parser.java

diff --git a/src/edu/berkeley/sbp/Parser.java b/src/edu/berkeley/sbp/Parser.java
index 3fad1dd..58d0bc2 100644 (file)
--- a/src/edu/berkeley/sbp/Parser.java
+++ b/src/edu/berkeley/sbp/Parser.java
@@ -22,7 +22,15 @@ public abstract class Parser<T extends Token, R> {
 
 
     /** 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 {
@@ -139,6 +147,27 @@ public abstract class Parser<T extends Token, R> {
         /** a single state in the LR table and the transitions possible from it */
         public class State implements Comparable<Table.State>, Iterable<Position> {
         
+            /*
+            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;
 
@@ -265,7 +294,7 @@ public abstract class Parser<T extends Token, R> {
         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) {
@@ -289,6 +318,13 @@ public abstract class Parser<T extends Token, R> {
                 return reduce(parent, numPop-1, rex, onlychild, target);
             }
 
+            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
             private Forest reduce(GSS.Phase.Node parent, int pos, Forest rex, GSS.Phase.Node onlychild, GSS.Phase target) {
                 if (pos>=0) holder[pos] = parent.pending();