UnwrapLeft, error reporting improvements

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

diff --git a/src/edu/berkeley/sbp/Sequence.java b/src/edu/berkeley/sbp/Sequence.java
index 0ce5f55..c41be4f 100644 (file)
--- a/src/edu/berkeley/sbp/Sequence.java
+++ b/src/edu/berkeley/sbp/Sequence.java
@@ -20,7 +20,7 @@ public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
     final HashSet<Sequence> needs  = new HashSet<Sequence>();
     final HashSet<Sequence> hates  = new HashSet<Sequence>();
 
-    // FIXME: these are ugly -- migrate into Cache
+    // FIXME: these are ugly -- migrate into Grammar
     HashMap<Sequence,Boolean> canNeed = new HashMap<Sequence,Boolean>();
     HashMap<Sequence,Boolean> canKill = new HashMap<Sequence,Boolean>();
 
@@ -54,6 +54,11 @@ public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
             ? new Unwrap(e, head, drop)
             : new RewritingSequence(head, e, drop);
     }
+    public static Sequence createLeft(Object head, Element[] e, boolean[] drop, boolean foster) {
+        return foster
+            ? new UnwrapLeft(e, head, drop)
+            : new RewritingSequence(head, e, drop);
+    }
 
     /** return a new sequence identical to this one, but with a positive conjunct <tt>s</tt> */
     public Sequence and(Sequence s) {
@@ -104,7 +109,7 @@ public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
         this.firstp = new Position(0, null);
     }
 
-    abstract Forest epsilonForm(Input.Region loc, Cache cache);
+    abstract Forest epsilonForm(Input.Region loc, Grammar cache);
 
     protected abstract <T> Forest<T> postReduce(Input.Region loc, Forest<T>[] args, Position p);
 
@@ -154,7 +159,7 @@ public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
 
         // Position /////////////////////////////////////////////////////////////////////////////////
 
-        final <T> Forest<T> rewrite(Input.Region loc, Cache cache) {
+        final <T> Forest<T> rewrite(Input.Region loc, Grammar cache) {
             if (this==firstp()) epsilonForm(loc, cache);
             for(int i=0; i<pos; i++) if (holder[i]==null) throw new Error("realbad " + i);
             for(int i=pos; i<elements.length; i++) {
@@ -219,7 +224,7 @@ public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
         public <T> Forest<T> postReduce(Input.Region loc, Forest<T>[] args, Position p) {
             return (Forest<T>)Forest.create(loc, result, null, false);
         }
-        Forest epsilonForm(Input.Region loc, Cache cache) {
+        Forest epsilonForm(Input.Region loc, Grammar cache) {
             return Forest.create(loc, result, null, false);
         }
     }
@@ -230,7 +235,7 @@ public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
         public Singleton(Element[] e, int idx) { super(e); this.idx = idx; }
         public <T> Forest<T> postReduce(Input.Region loc, Forest<T>[] args, Position p) { return args[idx]; }
         Sequence _clone() { return new Singleton(elements,idx); }
-        Forest epsilonForm(Input.Region loc, Cache cache) {
+        Forest epsilonForm(Input.Region loc, Grammar cache) {
             return ((Union)elements[idx]).epsilonForm(loc, cache);
         }
     }
@@ -251,7 +256,28 @@ public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
             for(int i=0; i<args.length; i++) if (!drops[i]) args2[j++] = args[i];
             return Forest.create(loc, (T)tag, args2, true);
         }
-        Forest epsilonForm(Input.Region loc, Cache cache) {
+        Forest epsilonForm(Input.Region loc, Grammar cache) {
+            return Forest.create(loc, tag, new Forest[0], false);
+        }
+    }
+
+    static class UnwrapLeft extends Sequence {
+        private boolean[] drops;
+        private final Object tag;
+        public UnwrapLeft(Element[] e, Object tag)                  { this(e, tag, null); }
+        public UnwrapLeft(Element[] e, Object tag, boolean[] drops) { super(e); this.drops = drops; this.tag = tag; }
+        Sequence _clone() { return new UnwrapLeft(elements, tag, drops); }
+        public <T> Forest<T> postReduce(Input.Region loc, Forest<T>[] args, Position p) {
+            for(int i=0; i<args.length; i++) if (args[i]==null) throw new Error();
+            if (drops==null) return Forest.create(loc, (T)tag, args, false, true);
+            int count = 0;
+            for(int i=0; i<drops.length; i++) if (!drops[i]) count++;
+            Forest<T>[] args2 = new Forest[count];
+            int j = 0;
+            for(int i=0; i<args.length; i++) if (!drops[i]) args2[j++] = args[i];
+            return Forest.create(loc, (T)tag, args2, false, true);
+        }
+        Forest epsilonForm(Input.Region loc, Grammar cache) {
             return Forest.create(loc, tag, new Forest[0], false);
         }
     }
@@ -284,7 +310,7 @@ public abstract class Sequence implements Iterable<Element>, SequenceOrElement {
             if (spacing) for(int i=0; i<50-len; i++) sb.append(' ');
             return sb;
         }
-        Forest epsilonForm(Input.Region loc, Cache cache) {
+        Forest epsilonForm(Input.Region loc, Grammar cache) {
             return Forest.create(loc, tag, new Forest[0], false);
         }
     }