refactoring to eliminate Token.result()

[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 ab06889..6bf274d 100644 (file)
--- a/src/edu/berkeley/sbp/Parser.java
+++ b/src/edu/berkeley/sbp/Parser.java
@@ -9,7 +9,7 @@ import java.util.*;
 import java.lang.reflect.*;
 
 /** a parser which translates streams of Tokens of type T into a Forest<R> */
 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;
 
 
     private final Table pt;
 

@@ -24,16 +24,15 @@ public class Parser<T extends Token, R> {
         if (p.element() != null) reachable(p.element(), h);
     }
 
         if (p.element() != null) reachable(p.element(), h);
     }
 

-    //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>
     /**
      *  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);
+    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> 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(); }

@@ -46,7 +45,8 @@ public class Parser<T extends Token, R> {
         for(;;) {
             GSS.Phase next = gss.new Phase(current, input.next());
             current.reduce();
         for(;;) {
             GSS.Phase next = gss.new Phase(current, input.next());
             current.reduce();

-            current.shift(next);
+            Forest forest = current.token==null ? null : shiftedToken((T)current.token);
+            current.shift(next, forest);

             if (current.isDone()) return (Forest<R>)current.finalResult;
             current.checkFailure();
             current = next;
             if (current.isDone()) return (Forest<R>)current.finalResult;
             current.checkFailure();
             current = next;

@@ -80,12 +80,13 @@ public class Parser<T extends Token, R> {
 
     // Table //////////////////////////////////////////////////////////////////////////////
 
 
     // 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 Sequence start0seq;
     /** an SLR(1) parse table which may contain conflicts */
     static class Table {
 
         private final Union start0 = new Top();
         private final Sequence start0seq;

-        static class Top extends Union { public Top() { super("0"); } }

         
         public final Walk.Cache cache = new Walk.Cache();
         
         
         public final Walk.Cache cache = new Walk.Cache();