X-Git-Url: http://git.megacz.com/?p=sbp.git;a=blobdiff_plain;f=src%2Fedu%2Fberkeley%2Fsbp%2Fmeta%2FGrammarAST.java;h=297886b36f69cfe5427d71d5020aacf9a04b2dc5;hp=87f7789269cabbfdc1a2a102567439de866a140a;hb=d474c27d3c37b00d2b2ec2dc62d123d69c8edac9;hpb=67d5def8fede01f412905fb5ff968b79894166fb

diff --git a/src/edu/berkeley/sbp/meta/GrammarAST.java b/src/edu/berkeley/sbp/meta/GrammarAST.java
index 87f7789..297886b 100644
--- a/src/edu/berkeley/sbp/meta/GrammarAST.java
+++ b/src/edu/berkeley/sbp/meta/GrammarAST.java
@@ -17,6 +17,14 @@ import java.io.*;
 public class GrammarAST {
 
     /**
+     *  Returns a Union representing the metagrammar (<tt>meta.g</tt>); the Tree produced by
+     *  parsing with this Union should be provided to <tt>buildFromAST</tt>
+     */
+    public static Union getMetaGrammar() {
+        return buildFromAST(MetaGrammar.meta, "s", new File[0]);
+    }
+
+    /**
      *  Create a grammar from a parse tree and binding resolver
      * 
      *  @param t   a tree produced by parsing a grammar using the metagrammar
@@ -27,10 +35,6 @@ public class GrammarAST {
         return new GrammarAST(includes, "").buildGrammar(grammarAST, startingNonterminal);
     }
 
-    public static Union getMetaGrammar() {
-        return MetaGrammar.newInstance();
-    }
-
     private static Object illegalTag = ""; // this is the tag that should never appear in the non-dropped output FIXME
 
     // Instance //////////////////////////////////////////////////////////////////////////////
@@ -88,7 +92,6 @@ public class GrammarAST {
         if (head.equals("Elements")) return new Seq((ElementNode[])Reflection.rebuild(walkChildren(t), ElementNode[].class));
         if (head.equals("NonTerminalReference")) return new ReferenceNode(stringifyChildren(t.child(0)));
         if (head.equals(")"))   return new ReferenceNode(stringifyChildren(t.child(0)), true);
-        if (head.equals("{"))   return new BracedNode(walkSeq(t.child(0)));
         if (head.equals("::"))  return walkSeq(t.child(1)).tag(walkString(t.child(0)));
         if (head.equals("...")) return new DropNode(new RepeatNode(new TildeNode(new AtomNode()), null, true,  true,  false));
 
@@ -104,15 +107,15 @@ public class GrammarAST {
 
         if (head.equals("!"))   return new DropNode(walkElement(t.child(0)));
         if (head.equals("^"))   return new LiteralNode(walkString(t.child(0)), true);
-        if (head.equals("`"))   return walkElement(t.child(0)).lifted();
+        if (head.equals("`"))   return new BacktickNode(walkElement(t.child(0)));
         if (head.equals("Quoted")) return stringifyChildren(t);
         if (head.equals("Literal")) return new LiteralNode(walkString(t.child(0)));
         if (head.equals("->")) return walkSeq(t.child(0)).follow(walkElement(t.child(1)));
         if (head.equals("DropNT")) return new NonTerminalNode(walkString(t.child(0)), (Seq[][])walkChildren(t.child(1)), false, null, true);
         if (head.equals("=")) return new NonTerminalNode(walkString(t.child(0)), (Seq[][])walk(t.child(2)),
                                                          true, t.size()==2 ? null : walkString(t.child(1)), false);
-        if (head.equals("&"))   return and2(walkSeq(t.child(0)), walkSeq(t.child(1)));
-        if (head.equals("&~"))  return andnot2(walkSeq(t.child(0)), walkSeq(t.child(1)));
+        if (head.equals("&"))   return walkSeq(t.child(0)).and(walkSeq(t.child(1)));
+        if (head.equals("&~"))  return walkSeq(t.child(0)).andnot(walkSeq(t.child(1)));
         if (head.equals("/"))   return (walkSeq(t.child(0))).separate(walkElement(t.child(1)));
         if (head.equals("()"))  return new LiteralNode("");
         if (head.equals("["))   return new AtomNode((char[][])Reflection.rebuild(walkChildren(t), char[][].class));
@@ -151,7 +154,7 @@ public class GrammarAST {
                 try {
                     String newPrefix = t.size()<2 ? "" : (walkString(t.child(1))+".");
                     FileInputStream fis = new FileInputStream(file);
-                    Tree tr = new CharParser(MetaGrammar.newInstance()).parse(fis).expand1();
+                    Tree tr = new CharParser(getMetaGrammar()).parse(fis).expand1();
                     return (GrammarNode)new GrammarAST(includes, newPrefix).walk(tr);
                 } catch (Exception e) {
                     throw new RuntimeException("while parsing " + file, e);
@@ -204,6 +207,14 @@ public class GrammarAST {
         }
     }
 
+    /** a node in the AST which is resolved into an Element */
+    private abstract class ElementNode {
+        public boolean isLifted() { return false; }
+        public boolean drop(Context cx) { return false; }
+        public Atom toAtom(Context cx) { throw new Error("can't convert a " + this.getClass().getName() + " to an atom: " + this); }
+        public abstract Element build(Context cx, NonTerminalNode cnt, boolean dropall);
+    }
+
     private class UnionNode extends ElementNode {
         public Seq[][] sequences;
         public String  sep = null;
@@ -302,7 +313,6 @@ public class GrammarAST {
             for(int i=0; i<elements.length; i++) {
                 if (elements[i]==null)
                     throw new RuntimeException();
-                elements[i].ownerSeq = this;
             }
             // FIXME: this whole mechanism is sketchy
             if (check)
@@ -331,8 +341,8 @@ public class GrammarAST {
         }
         public Seq tag(String tag) { this.tag = tag; return this; }
         public Seq follow(ElementNode follow) { this.follow = follow; return this; }
-        public Seq and(Seq s) { and.add(s); return this; }
-        public Seq andnot(Seq s) { not.add(s); return this; }
+        public Seq and(Seq s) { and.add(s); s.alwaysDrop = true; return this; }
+        public Seq andnot(Seq s) { not.add(s); s.alwaysDrop = true; return this; }
         public Seq separate(ElementNode sep) {
             ElementNode[] elements = new ElementNode[this.elements.length * 2 - 1];
             for(int i=0; i<this.elements.length; i++) {
@@ -357,8 +367,10 @@ public class GrammarAST {
             for(int i=0; i<elements.length; i++) {
                 if (dropall) drops[i] = true;
                 else         drops[i] = elements[i].drop(cx);
-                if (elements[i].getOwnerTag() != null)
-                    tag = elements[i].getOwnerTag();
+                if (elements[i] instanceof LiteralNode && ((LiteralNode)elements[i]).caret) {
+                    if (tag != null) throw new RuntimeException("cannot have multiple tags in a sequence: " + this);
+                    tag = ((LiteralNode)elements[i]).getLiteralTag();
+                }
             }
             Sequence ret = null;
             int idx = -1;
@@ -378,7 +390,7 @@ public class GrammarAST {
                 throw new RuntimeException("multiple non-dropped elements in sequence: " + Sequence.create("", els));
             boolean[] lifts = new boolean[elements.length];
             for(int i=0; i<elements.length; i++)
-                lifts[i] = elements[i].lifted;
+                lifts[i] = elements[i].isLifted();
             if (!multiNonDrop) {
                 if (idx == -1) 
                     ret = tag==null
@@ -416,10 +428,6 @@ public class GrammarAST {
         }
         public boolean drop(Context cx) { return resolve(cx).drop(cx); }
         public Element build(Context cx, NonTerminalNode cnt, boolean dropall) {
-            /*
-            if (!this.nonTerminal.startsWith(prefix))
-                nonTerminal = prefix + nonTerminal;
-            */
             Element ret = cx.get(nonTerminal);
             if (ret == null) throw new RuntimeException("unknown nonterminal \""+nonTerminal+"\"");
             return ret;
@@ -435,7 +443,7 @@ public class GrammarAST {
             this.string = string;
             this.caret = caret;
         }
-        public String getOwnerTag() { return caret ? thePrefix+string : super.getOwnerTag(); }
+        public String getLiteralTag() { return caret ? thePrefix+string : null; }
         public String toString() { return "\""+string+"\""; }
         public boolean drop(Context cx) { return true; }
         public Atom toAtom(Context cx) {
@@ -486,25 +494,19 @@ public class GrammarAST {
         }
     }
 
-    private abstract class ElementNode {
-        public boolean lifted = false;
-        public Seq ownerSeq = null;
-        public String getOwnerTag() { return null; }
-        public ElementNode lifted() { this.lifted = true; return this; }
-        public boolean drop(Context cx) { return false; }
-        public Atom toAtom(Context cx) { throw new Error("can't convert a " + this.getClass().getName() + " to an atom: " + this); }
-        public abstract Element build(Context cx, NonTerminalNode cnt, boolean dropall);
-    }
-
     private abstract class ElementNodeWrapper extends ElementNode {
         protected ElementNode _e;
         public ElementNodeWrapper(ElementNode e) { this._e = e; }
-        public String getOwnerTag() { return _e.getOwnerTag(); }
         public boolean drop(Context cx) { return _e.drop(cx); }
         public Atom toAtom(Context cx) { return _e.toAtom(cx); }
         public Element build(Context cx, NonTerminalNode cnt, boolean dropall) { return _e.build(cx, cnt, dropall); }
     }
 
+    private class BacktickNode extends ElementNodeWrapper {
+        public BacktickNode(ElementNode e) { super(e); }
+        public boolean isLifted() { return true; }
+    }
+
     private class TildeNode extends ElementNodeWrapper {
         public TildeNode(ElementNode e) { super(e); }
         public Atom toAtom(Context cx) { return (Atom)((Topology<Character>)_e.toAtom(cx).complement()); }
@@ -516,26 +518,6 @@ public class GrammarAST {
         public boolean drop(Context cx) { return true; }
     }
 
-    // FIXME: doesn't this require a tag?
-    private class BracedNode extends ElementNode {
-        public Seq body;
-        public BracedNode(Seq seq) { this.body = seq; }
-        public Element build(Context cx, NonTerminalNode cnt, boolean dropall) {
-            Union u = new Union(null, false);
-            Sequence s = body.build(cx, u, null, dropall);
-            Union u2 = new Union(null, false);
-            u2.add(Sequence.create(new Element[] {
-                CharAtom.leftBrace,
-                u,
-                CharAtom.rightBrace
-            }, 1));
-            return u2;
-        }
-    }
-
-    public Seq  and2(Seq s,    Seq a) { a.alwaysDrop = true; return s.and(a);    }
-    public Seq  andnot2(Seq s, Seq a) { a.alwaysDrop = true; return s.andnot(a); }
-
     //////////////////////////////////////////////////////////////////////////////
 
     public class Context {