src/edu/berkeley/sbp/Forest.java

   1 // Copyright 2006 all rights reserved; see LICENSE file for BSD-style license
   2
   3 package edu.berkeley.sbp;
   4 import edu.berkeley.sbp.*;
   5 import edu.berkeley.sbp.Sequence.Position;
   6 import edu.berkeley.sbp.util.*;
   7 import java.io.*;
   8 import java.util.*;
   9 import java.lang.reflect.*;
  10
  11 /**
  12  *   <font color=blue>
  13  *   An efficient representation of a collection of trees (Tomita's
  14  *   shared packed parse forest).
  15  *   </font>
  16  */
  17 public abstract class Forest<NodeType> implements GraphViz.ToGraphViz {
  18
  19     /** assume that this forest contains exactly one tree and return it; otherwise throw an exception */
  20     public abstract Tree<NodeType> expand1() throws Ambiguous;
  21
  22     /** expand this forest into a set of trees */
  23     public void expand(HashSet<Tree<NodeType>> ht) { expand(ht, new HashSet<Forest<NodeType>>(), null); }
  24
  25     static <NodeType> Forest<NodeType> create(Input.Region loc, NodeType head, Forest<NodeType>[] children, boolean lift) {
  26         if (loc == null) throw new RuntimeException("invoked Forest.create(null,,,,) -- this should never happen");
  27         return new One<NodeType>(loc, head, children, lift);
  28     }
  29
  30     /** create a new forest */
  31     public static <NodeType> Forest<NodeType> create(Input.Region loc, NodeType head, Forest<NodeType>[] children) {
  32         return Forest.create(loc, head, children, false); }
  33
  34     // Package-Private //////////////////////////////////////////////////////////////////////////////
  35
  36     abstract void expand(HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus);
  37     abstract void gather(HashSet<Forest<NodeType>> ignore);
  38     abstract void edges(GraphViz.Node n);
  39     boolean ambiguous() { return false; }
  40
  41     abstract Input.Region getRegion();
  42
  43     // One //////////////////////////////////////////////////////////////////////////////
  44
  45     /** A "single" forest with a head and child subforests */
  46     private static class One<NodeType> extends Forest<NodeType> {
  47
  48         private final Input.Region      location;
  49         private final NodeType                head;
  50         private final Forest<NodeType>[]       children;
  51
  52         /** if true, the last child's children are considered children of this node */
  53         private final boolean           lift;
  54
  55         Input.Region getRegion() { return location; }
  56
  57         private One(Input.Region loc, NodeType head, Forest<NodeType>[] children, boolean lift) {
  58             this.location = loc;
  59             this.head = head;
  60             if (head==null) throw new RuntimeException("invoked Forest.create(,null,,,) -- this should never happen");
  61             this.children = children==null ? emptyForestArray : new Forest[children.length];
  62             if (children != null) System.arraycopy(children, 0, this.children, 0, children.length);
  63             if (children != null) for(int i=0; i<children.length; i++) if (children[i]==null) throw new Error(i+"");
  64             this.lift = lift;
  65         }
  66
  67         public Tree<NodeType> expand1() throws Ambiguous {
  68             Tree<NodeType>[] ret = new Tree[children.length];
  69             for(int i=0; i<children.length; i++) ret[i] = children[i].expand1();
  70             return new Tree<NodeType>(location, head, ret, lift);
  71         }
  72
  73         void gather(HashSet<Forest<NodeType>> hf) {
  74             hf.add(this);
  75             for(Forest<NodeType> f : children) f.gather(hf);
  76         }
  77         void expand(HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus) {
  78             if (ignore.contains(this)) { ht.add(bogus); return; }
  79             expand(0, new Tree[children.length], ht, ignore, bogus);
  80         }
  81         private void expand(final int i, Tree<NodeType>[] ta, HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus) {
  82             if (i==children.length) {
  83                 ht.add(new Tree<NodeType>(location, head, ta, lift));
  84             } else {
  85                 HashSet<Tree<NodeType>> ht2 = new HashSet<Tree<NodeType>>();
  86                 children[i].expand(ht2, ignore, bogus);
  87                 for(Tree<NodeType> tc : ht2) {
  88                     ta[i] = tc;
  89                     expand(i+1, ta, ht, ignore, bogus);
  90                     ta[i] = null;
  91                 }
  92             }
  93         }
  94
  95         // GraphViz, ToInt //////////////////////////////////////////////////////////////////////////////
  96
  97         public boolean isTransparent() { return false; }
  98         public boolean isHidden() { return false; }
  99         public GraphViz.Node toGraphViz(GraphViz gv) {
 100             if (gv.hasNode(this)) return gv.createNode(this);
 101             GraphViz.Node n = gv.createNode(this);
 102             n.label = headToString()==null?"":headToString();
 103             n.directed = true;
 104             edges(n);
 105             return n;
 106         }
 107         boolean edges = false; // FIXME ??
 108         public void edges(GraphViz.Node n) {
 109             if (edges) return;
 110             edges = true;
 111             for(int i=0; i<children.length; i++) {
 112                 if (i==children.length-1 && lift && !children[i].ambiguous()) {
 113                     children[i].edges(n);
 114                 } else {
 115                     n.edge(children[i], null);
 116                 }
 117             }
 118         }
 119
 120         protected String  headToString()         { return head==null?null:head.toString(); }
 121         protected String  headToJava()           { return "null"; }
 122         protected String  left()                 { return "{"; }
 123         protected String  right()                { return "}"; }
 124         protected boolean ignoreSingleton()      { return false; }
 125     }
 126
 127
 128     // Many //////////////////////////////////////////////////////////////////////////////
 129
 130     /** An "ambiguity node"; this is immutable once it has been "looked at" */
 131     static class Many<NodeType> extends Forest<NodeType> {
 132
 133         private FastSet<Forest<NodeType>> hp = new FastSet<Forest<NodeType>>();
 134         private boolean touched = false;
 135
 136         public Many() { }
 137
 138         Input.Region getRegion() { return hp.iterator().next().getRegion(); } // all should be identical
 139
 140         public Tree<NodeType> expand1() throws Ambiguous {
 141             touched();
 142             if (hp.size() > 1) {
 143                 HashSet<Forest<NodeType>> hf0 = new HashSet<Forest<NodeType>>();
 144                 Iterator<Forest<NodeType>> ih = hp.iterator();
 145                 ih.next().gather(hf0);
 146                 for(Forest<NodeType> f : hp) {
 147                     HashSet<Forest<NodeType>> hf1 = new HashSet<Forest<NodeType>>();
 148                     f.gather(hf1);
 149                     hf0.retainAll(hf1);
 150                 }
 151                 HashSet<Tree<NodeType>> ht = new HashSet<Tree<NodeType>>();
 152                 expand(ht, hf0, new Tree(null, "*"));
 153                 throw new Ambiguous((Forest<?>)this,
 154                                     (HashSet<Tree<?>>)(Object)ht);
 155             }
 156             return hp.iterator().next().expand1();
 157         }
 158
 159         void gather(HashSet<Forest<NodeType>> ht) {
 160             touched();
 161
 162             // FIXME: do something more sensible here
 163             if (ht.contains(this)) {
 164                 System.err.println("WARNING: grammar produced a circular forest\n" + this);
 165                 //throw new Error("grammar produced a circular forest:\n" + this);
 166                 return;
 167             }
 168
 169             ht.add(this);
 170             for(Forest<NodeType> f : hp) f.gather(ht);
 171         }
 172
 173         private void touched() {
 174             if (touched) return;
 175             touched = true;
 176             /*
 177             FastSet<Forest<NodeType>> f2 = new FastSet<Forest<NodeType>>();
 178             for(Forest f : hp)
 179                 if (f instanceof Forest.One) f2.add(f);
 180                 else for(Forest ff : ((Forest.Many<NodeType>)f))
 181                     f2.add(ff);
 182             hp = f2;
 183             */
 184         }
 185         public boolean contains(Forest f) {
 186             touched();
 187             return hp.contains(f);
 188         }
 189         public void merge(Forest p) {
 190             if (touched) throw new RuntimeException("attempt to merge() on a Forest.Many that has already been examined");
 191             if (p==this) throw new RuntimeException("attempt to merge() a Forest.Many to itself!");
 192             hp.add(p, true);
 193         }
 194         boolean ambiguous() {
 195             touched();
 196             if (hp.size()==0) return false;
 197             if (hp.size()==1) return hp.iterator().next().ambiguous();
 198             return true;
 199         }
 200
 201         void expand(HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus) {
 202             touched();
 203             if (ignore.contains(this)) { ht.add(bogus); return; }
 204             for (Forest<NodeType> f : hp) f.expand(ht, ignore, bogus);
 205         }
 206
 207
 208         // GraphViz, ToInt //////////////////////////////////////////////////////////////////////////////
 209
 210         public boolean isTransparent() { return hp.size()==1; }
 211         public boolean isHidden() { return hp.size()==0; }
 212         public void edges(GraphViz.Node n) {
 213             if (hp.size()==1) { hp.iterator().next().edges(n); return; }
 214             for(Forest f : hp) f.edges(n);
 215         }
 216         public GraphViz.Node toGraphViz(GraphViz gv) {
 217             if (hp.size()==1) return hp.iterator().next().toGraphViz(gv);
 218             if (gv.hasNode(this)) return gv.createNode(this);
 219             GraphViz.Node n = gv.createNode(this);
 220             n.label = "?";
 221             n.color = "red";
 222             for(Forest f : hp) n.edge(f, null);
 223             return n;
 224         }
 225     }
 226
 227     // Statics //////////////////////////////////////////////////////////////////////////////
 228
 229     private static Tree[] tree_hint = new Tree[0];
 230     private static String[] string_hint = new String[0];
 231     private static final Forest[] emptyForestArray = new Forest[0];
 232
 233     protected String  headToString()    { return null; }
 234     protected String  headToJava()      { return "null"; }
 235     protected String  left()            { return "<?"; }
 236     protected String  right()           { return "?>"; }
 237     protected boolean ignoreSingleton() { return true; }
 238 }