src/edu/berkeley/sbp/Forest.java

   1 // Copyright 2006-2007 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     public static <NodeType> Forest<NodeType> create(Input.Region region, NodeType head, Forest<NodeType>[] children) {
  32         return create(region, head, children, new boolean[children==null ? 0 : children.length]); }
  33     public static <NodeType> Forest<NodeType> create(Input.Region region, NodeType head, Forest<NodeType>[] children, boolean[] lifts) {
  34         if (region == null) throw new RuntimeException("invoked Forest.create(region=null) -- this should never happen");
  35         return new One<NodeType>(region, head, children, lifts);
  36     }
  37
  38     abstract void expand(HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus);
  39     abstract void gather(HashSet<Forest<NodeType>> ignore);
  40     abstract void edges(GraphViz.Node n);
  41     boolean ambiguous() { return false; }
  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[]         lifts;
  54
  55         public Input.Region getRegion() { return location; }
  56
  57         private One(Input.Region loc, NodeType head, Forest<NodeType>[] children, boolean[] lifts) {
  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.lifts = lifts;
  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, lifts);
  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,
  82                             Tree<NodeType> bogus) {
  83             if (i==children.length) {
  84                 ht.add(new Tree<NodeType>(location, head, ta, lifts));
  85             } else {
  86                 HashSet<Tree<NodeType>> ht2 = new HashSet<Tree<NodeType>>();
  87                 children[i].expand(ht2, ignore, bogus);
  88                 for(Tree<NodeType> tc : ht2) {
  89                     ta[i] = tc;
  90                     expand(i+1, ta, ht, ignore, bogus);
  91                     ta[i] = null;
  92                 }
  93             }
  94         }
  95
  96         // GraphViz, ToInt //////////////////////////////////////////////////////////////////////////////
  97
  98         public boolean isTransparent() { return false; }
  99         public boolean isHidden() { return false; }
 100         public GraphViz.Node toGraphViz(GraphViz gv) {
 101             if (gv.hasNode(this)) return gv.createNode(this);
 102             GraphViz.Node n = gv.createNode(this);
 103             n.label = headToString()==null?"":headToString();
 104             n.directed = true;
 105             edges(n);
 106             return n;
 107         }
 108         boolean edges = false; // FIXME ??
 109         public void edges(GraphViz.Node n) {
 110             if (edges) return;
 111             edges = true;
 112             for(int i=0; i<children.length; i++) {
 113                 if (lifts[i] && !children[i].ambiguous()) {
 114                     children[i].edges(n);
 115                 } else {
 116                     n.edge(children[i], null);
 117                 }
 118             }
 119         }
 120
 121         protected String  headToString()         { return head==null?null:head.toString(); }
 122         protected String  headToJava()           { return "null"; }
 123         protected String  left()                 { return "{"; }
 124         protected String  right()                { return "}"; }
 125         protected boolean ignoreSingleton()      { return false; }
 126     }
 127
 128
 129     // Many //////////////////////////////////////////////////////////////////////////////
 130
 131     /** An "ambiguity node"; this is immutable once it has been "looked at" */
 132     static class Many<NodeType> extends Forest<NodeType> {
 133
 134         private FastSet<Forest<NodeType>> hp = new FastSet<Forest<NodeType>>();
 135         private boolean touched = false;
 136
 137         public Many() { }
 138
 139         public Input.Region getRegion() { return hp.iterator().next().getRegion(); } // all should be identical
 140
 141         public Tree<NodeType> expand1() throws Ambiguous {
 142             touched();
 143             if (hp.size() > 1) {
 144                 HashSet<Forest<NodeType>> hf0 = new HashSet<Forest<NodeType>>();
 145                 Iterator<Forest<NodeType>> ih = hp.iterator();
 146                 ih.next().gather(hf0);
 147                 for(Forest<NodeType> f : hp) {
 148                     HashSet<Forest<NodeType>> hf1 = new HashSet<Forest<NodeType>>();
 149                     f.gather(hf1);
 150                     hf0.retainAll(hf1);
 151                 }
 152                 HashSet<Tree<NodeType>> ht = new HashSet<Tree<NodeType>>();
 153                 expand(ht, hf0, new Tree(null, "*"));
 154                 throw new Ambiguous((Forest<?>)this,
 155                                     (HashSet<Tree<?>>)(Object)ht);
 156             }
 157             return hp.iterator().next().expand1();
 158         }
 159
 160         void gather(HashSet<Forest<NodeType>> ht) {
 161             touched();
 162
 163             // FIXME: do something more sensible here
 164             if (ht.contains(this)) {
 165                 System.err.println("WARNING: grammar produced a circular forest\n" + this);
 166                 //throw new Error("grammar produced a circular forest:\n" + this);
 167                 return;
 168             }
 169
 170             ht.add(this);
 171             for(Forest<NodeType> f : hp) f.gather(ht);
 172         }
 173
 174         private void touched() {
 175             if (touched) return;
 176             touched = true;
 177             /*
 178             FastSet<Forest<NodeType>> f2 = new FastSet<Forest<NodeType>>();
 179             for(Forest f : hp)
 180                 if (f instanceof Forest.One) f2.add(f);
 181                 else for(Forest ff : ((Forest.Many<NodeType>)f))
 182                     f2.add(ff);
 183             hp = f2;
 184             */
 185         }
 186         public boolean contains(Forest f) {
 187             touched();
 188             return hp.contains(f);
 189         }
 190         public void merge(Forest p) {
 191             if (touched) throw new RuntimeException("attempt to merge() on a Forest.Many that has already been examined");
 192             if (p==this) throw new RuntimeException("attempt to merge() a Forest.Many to itself!");
 193             hp.add(p, true);
 194         }
 195         boolean ambiguous() {
 196             touched();
 197             if (hp.size()==0) return false;
 198             if (hp.size()==1) return hp.iterator().next().ambiguous();
 199             return true;
 200         }
 201
 202         void expand(HashSet<Tree<NodeType>> ht, HashSet<Forest<NodeType>> ignore, Tree<NodeType> bogus) {
 203             touched();
 204             if (ignore.contains(this)) { ht.add(bogus); return; }
 205             for (Forest<NodeType> f : hp) f.expand(ht, ignore, bogus);
 206         }
 207
 208
 209         // GraphViz, ToInt //////////////////////////////////////////////////////////////////////////////
 210
 211         public boolean isTransparent() { return hp.size()==1; }
 212         public boolean isHidden() { return hp.size()==0; }
 213         public void edges(GraphViz.Node n) {
 214             if (hp.size()==1) { hp.iterator().next().edges(n); return; }
 215             for(Forest f : hp) f.edges(n);
 216         }
 217         public GraphViz.Node toGraphViz(GraphViz gv) {
 218             if (hp.size()==1) return hp.iterator().next().toGraphViz(gv);
 219             if (gv.hasNode(this)) return gv.createNode(this);
 220             GraphViz.Node n = gv.createNode(this);
 221             n.label = "?";
 222             n.color = "red";
 223             for(Forest f : hp) n.edge(f, null);
 224             return n;
 225         }
 226     }
 227
 228     // Statics //////////////////////////////////////////////////////////////////////////////
 229
 230     private static Tree[] tree_hint = new Tree[0];
 231     private static String[] string_hint = new String[0];
 232     private static final Forest[] emptyForestArray = new Forest[0];
 233
 234     protected String  headToString()    { return null; }
 235     protected String  headToJava()      { return "null"; }
 236     protected String  left()            { return "<?"; }
 237     protected String  right()           { return "?>"; }
 238     protected boolean ignoreSingleton() { return true; }
 239 }