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.util.*;
   5 import java.io.*;
   6 import java.util.*;
   7
   8 /**
   9  *   <font color=blue>
  10  *   An efficient representation of a collection of trees (Tomita's
  11  *   shared packed parse forest).
  12  *   </font>
  13  */
  14 public abstract class Forest<NodeType> implements GraphViz.ToGraphViz {
  15
  16     /** assume that this forest contains exactly one tree and return it; otherwise throw an exception */
  17     public abstract Tree<NodeType> expand1() throws Ambiguous;
  18
  19     /** expand this forest into a set of trees */
  20     public Iterable<Tree<NodeType>> expand() {
  21         HashSet<Tree<NodeType>> ht = new HashSet<Tree<NodeType>>();
  22         expand(ht, new HashSet<Forest<NodeType>>(), null);
  23         return ht;
  24     }
  25
  26     /** returns the input Region which this Forest was parsed from */
  27     public abstract Input.Region getRegion();
  28
  29     // Package-Private //////////////////////////////////////////////////////////////////////////////
  30
  31     static <NodeType> Forest<NodeType> create(Input.Region region, NodeType head, Forest<NodeType>[] children, boolean lift) {
  32         if (region == null) throw new RuntimeException("invoked Forest.create(region=null) -- this should never happen");
  33         return new One<NodeType>(region, head, children, lift);
  34     }
  35
  36     /** create a new forest */
  37     public static <NodeType> Forest<NodeType> create(Input.Region region, NodeType head, Forest<NodeType>[] children) {
  38         return Forest.create(region, head, children, false); }
  39
  40     abstract void expand(HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus);
  41     abstract void gather(HashSet<Forest<NodeType>> ignore);
  42     abstract void edges(GraphViz.Node n);
  43     boolean ambiguous() { return false; }
  44
  45     // One //////////////////////////////////////////////////////////////////////////////
  46
  47     /** A "single" forest with a head and child subforests */
  48     private static class One<NodeType> extends Forest<NodeType> {
  49
  50         private final Input.Region      location;
  51         private final NodeType                head;
  52         private final Forest<NodeType>[]       children;
  53
  54         /** if true, the last child's children are considered children of this node */
  55         private final boolean           lift;
  56
  57         public Input.Region getRegion() { return location; }
  58
  59         private One(Input.Region loc, NodeType head, Forest<NodeType>[] children, boolean lift) {
  60             this.location = loc;
  61             this.head = head;
  62             if (head==null) throw new RuntimeException("invoked Forest.create(,null,,,) -- this should never happen");
  63             this.children = children==null ? emptyForestArray : new Forest[children.length];
  64             if (children != null) System.arraycopy(children, 0, this.children, 0, children.length);
  65             if (children != null) for(int i=0; i<children.length; i++) if (children[i]==null) throw new Error(i+"");
  66             this.lift = lift;
  67         }
  68
  69         public Tree<NodeType> expand1() throws Ambiguous {
  70             Tree<NodeType>[] ret = new Tree[children.length];
  71             for(int i=0; i<children.length; i++) ret[i] = children[i].expand1();
  72             return new Tree<NodeType>(location, head, ret, lift);
  73         }
  74
  75         void gather(HashSet<Forest<NodeType>> hf) {
  76             hf.add(this);
  77             for(Forest<NodeType> f : children) f.gather(hf);
  78         }
  79         void expand(HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus) {
  80             if (ignore.contains(this)) { ht.add(bogus); return; }
  81             expand(0, new Tree[children.length], ht, ignore, bogus);
  82         }
  83         private void expand(final int i, Tree<NodeType>[] ta, HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore,
  84                             Tree<NodeType> bogus) {
  85             if (i==children.length) {
  86                 ht.add(new Tree<NodeType>(location, head, ta, lift));
  87             } else {
  88                 HashSet<Tree<NodeType>> ht2 = new HashSet<Tree<NodeType>>();
  89                 children[i].expand(ht2, ignore, bogus);
  90                 for(Tree<NodeType> tc : ht2) {
  91                     ta[i] = tc;
  92                     expand(i+1, ta, ht, ignore, bogus);
  93                     ta[i] = null;
  94                 }
  95             }
  96         }
  97
  98         // GraphViz, ToInt //////////////////////////////////////////////////////////////////////////////
  99
 100         public boolean isTransparent() { return false; }
 101         public boolean isHidden() { return false; }
 102         public GraphViz.Node toGraphViz(GraphViz gv) {
 103             if (gv.hasNode(this)) return gv.createNode(this);
 104             GraphViz.Node n = gv.createNode(this);
 105             n.label = headToString()==null?"":headToString();
 106             n.directed = true;
 107             edges(n);
 108             return n;
 109         }
 110         boolean edges = false; // FIXME ??
 111         public void edges(GraphViz.Node n) {
 112             if (edges) return;
 113             edges = true;
 114             for(int i=0; i<children.length; i++) {
 115                 if (i==children.length-1 && lift && !children[i].ambiguous()) {
 116                     children[i].edges(n);
 117                 } else {
 118                     n.edge(children[i], null);
 119                 }
 120             }
 121         }
 122
 123         protected String  headToString()         { return head==null?null:head.toString(); }
 124         protected String  headToJava()           { return "null"; }
 125         protected String  left()                 { return "{"; }
 126         protected String  right()                { return "}"; }
 127         protected boolean ignoreSingleton()      { return false; }
 128     }
 129
 130
 131     // Many //////////////////////////////////////////////////////////////////////////////
 132
 133     /** An "ambiguity node"; this is immutable once it has been "looked at" */
 134     static class Many<NodeType> extends Forest<NodeType> {
 135
 136         private FastSet<Forest<NodeType>> hp = new FastSet<Forest<NodeType>>();
 137         private boolean touched = false;
 138
 139         public Many() { }
 140
 141         public Input.Region getRegion() { return hp.iterator().next().getRegion(); } // all should be identical
 142
 143         public Tree<NodeType> expand1() throws Ambiguous {
 144             touched();
 145             if (hp.size() > 1) {
 146                 HashSet<Forest<NodeType>> hf0 = new HashSet<Forest<NodeType>>();
 147                 Iterator<Forest<NodeType>> ih = hp.iterator();
 148                 ih.next().gather(hf0);
 149                 for(Forest<NodeType> f : hp) {
 150                     HashSet<Forest<NodeType>> hf1 = new HashSet<Forest<NodeType>>();
 151                     f.gather(hf1);
 152                     hf0.retainAll(hf1);
 153                 }
 154                 HashSet<Tree<NodeType>> ht = new HashSet<Tree<NodeType>>();
 155                 expand(ht, hf0, new Tree(null, "*"));
 156                 throw new Ambiguous((Forest<?>)this,
 157                                     (HashSet<Tree<?>>)(Object)ht);
 158             }
 159             return hp.iterator().next().expand1();
 160         }
 161
 162         void gather(HashSet<Forest<NodeType>> ht) {
 163             touched();
 164
 165             // FIXME: do something more sensible here
 166             if (ht.contains(this)) {
 167                 System.err.println("WARNING: grammar produced a circular forest\n" + this);
 168                 //throw new Error("grammar produced a circular forest:\n" + this);
 169                 return;
 170             }
 171
 172             ht.add(this);
 173             for(Forest<NodeType> f : hp) f.gather(ht);
 174         }
 175
 176         private void touched() {
 177             if (touched) return;
 178             touched = true;
 179             /*
 180             FastSet<Forest<NodeType>> f2 = new FastSet<Forest<NodeType>>();
 181             for(Forest f : hp)
 182                 if (f instanceof Forest.One) f2.add(f);
 183                 else for(Forest ff : ((Forest.Many<NodeType>)f))
 184                     f2.add(ff);
 185             hp = f2;
 186             */
 187         }
 188         public boolean contains(Forest f) {
 189             touched();
 190             return hp.contains(f);
 191         }
 192         public void merge(Forest p) {
 193             if (touched) throw new RuntimeException("attempt to merge() on a Forest.Many that has already been examined");
 194             if (p==this) throw new RuntimeException("attempt to merge() a Forest.Many to itself!");
 195             hp.add(p, true);
 196         }
 197         boolean ambiguous() {
 198             touched();
 199             if (hp.size()==0) return false;
 200             if (hp.size()==1) return hp.iterator().next().ambiguous();
 201             return true;
 202         }
 203
 204         void expand(HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus) {
 205             touched();
 206             if (ignore.contains(this)) { ht.add(bogus); return; }
 207             for (Forest<NodeType> f : hp) f.expand(ht, ignore, bogus);
 208         }
 209
 210
 211         // GraphViz, ToInt //////////////////////////////////////////////////////////////////////////////
 212
 213         public boolean isTransparent() { return hp.size()==1; }
 214         public boolean isHidden() { return hp.size()==0; }
 215         public void edges(GraphViz.Node n) {
 216             if (hp.size()==1) { hp.iterator().next().edges(n); return; }
 217             for(Forest f : hp) f.edges(n);
 218         }
 219         public GraphViz.Node toGraphViz(GraphViz gv) {
 220             if (hp.size()==1) return hp.iterator().next().toGraphViz(gv);
 221             if (gv.hasNode(this)) return gv.createNode(this);
 222             GraphViz.Node n = gv.createNode(this);
 223             n.label = "?";
 224             n.color = "red";
 225             for(Forest f : hp) n.edge(f, null);
 226             return n;
 227         }
 228     }
 229
 230     // Statics //////////////////////////////////////////////////////////////////////////////
 231
 232     private static Tree[] tree_hint = new Tree[0];
 233     private static String[] string_hint = new String[0];
 234     private static final Forest[] emptyForestArray = new Forest[0];
 235
 236     protected String  headToString()    { return null; }
 237     protected String  headToJava()      { return "null"; }
 238     protected String  left()            { return "<?"; }
 239     protected String  right()           { return "?>"; }
 240     protected boolean ignoreSingleton() { return true; }
 241 }