src/edu/berkeley/sbp/Walk.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.util.*;
   6 import edu.berkeley.sbp.Sequence.Position;
   7 import java.io.*;
   8 import java.util.*;
   9 import java.lang.reflect.*;
  10 import java.lang.ref.*;
  11
  12 /** a traversal of the grammar performed by mapping from SequenceOrElements to a lattice and computing the resulting LUB */
  13 abstract class Walk<T> {
  14     protected HashSet<SequenceOrElement> acc = new HashSet<SequenceOrElement>();
  15     protected abstract T bottom(SequenceOrElement e);
  16
  17     protected final Cache c;
  18     public Walk() { this(null); }
  19     public Walk(Cache c) { this.c = c; }
  20
  21     public  T walkSequence(Sequence s) {
  22         T ret = bottom(s);
  23         for(Position p = s.firstp(); p!=null && !p.isLast(); p = p.next())
  24             ret = sequence(s, ret, walk(p.element()));
  25         return ret;
  26     }
  27
  28     public      T walkAtom(Atom r) { return walk(r); }
  29     public      T union(Union u, T a, T b) { return  bottom(u); }
  30     public      T sequence(Sequence s, T a, T b) { return  bottom(s); }
  31     protected   T walk(SequenceOrElement e) {
  32         if (acc.contains(e)) return bottom(e);
  33         acc.add(e);
  34         return walk2(e);
  35     }
  36
  37     protected T walk2(SequenceOrElement e) {
  38         if      (e instanceof Atom)     return walkAtom((Atom)e);
  39         else if (e instanceof Sequence) return walkSequence((Sequence)e);
  40         else if (e instanceof Union) {
  41             T ret = bottom(e);
  42             for(Sequence s : (Union)e)
  43                 ret = union((Union)e, ret, walk(s));
  44             return ret;
  45         } else {
  46             throw new Error("unknown element of class " + e.getClass().getName() + ": " + e);
  47         }
  48     }
  49
  50     static class YieldSet extends Walk<HashSet<SequenceOrElement>> {
  51         private final SequenceOrElement e;
  52         public final HashSet<SequenceOrElement> walk() { return walk(e); }
  53         public YieldSet(SequenceOrElement e, Cache c)  { super(c); this.e = e; }
  54         public HashSet<SequenceOrElement> bottom(SequenceOrElement e)     { return acc; }
  55         public HashSet<SequenceOrElement> walkSequence(Sequence seq) { return bottom(seq); }
  56         public HashSet<SequenceOrElement> walkAtom(Atom r) {
  57             c.atoms.put(e, c.atoms.get(e)==null ? r : c.atoms.get(e).union(r));
  58             return super.walkAtom(r);
  59         }
  60         protected HashSet<SequenceOrElement> walk2(SequenceOrElement e) {
  61             HashSet<SequenceOrElement> ret = super.walk2(e);
  62             if (e instanceof Union)
  63                 for(Sequence s : (Union)e) {
  64                     for(Sequence ss : s.needs()) ret = union((Union)e, ret, walk(ss));
  65                     for(Sequence ss : s.hates()) ret = union((Union)e, ret, walk(ss));
  66                 }
  67             return ret;
  68         }
  69     }
  70
  71     static class YieldSet2 extends Walk<HashSet<SequenceOrElement>> {
  72         private final SequenceOrElement e;
  73         public final HashSet<SequenceOrElement> walk() { return walk(e); }
  74         public YieldSet2(SequenceOrElement e, Cache c)  { super(c); this.e = e; }
  75         public HashSet<SequenceOrElement> bottom(SequenceOrElement e)     { return acc; }
  76         public HashSet<SequenceOrElement> walkSequence(Sequence seq) { return bottom(seq); }
  77         public HashSet<SequenceOrElement> walkAtom(Atom r) {
  78             c.atoms.put(e, c.atoms.get(e)==null ? r : c.atoms.get(e).union(r));
  79             return super.walkAtom(r);
  80         }
  81     }
  82
  83     static class EquivalentTo extends Walk<HashSet<Sequence>> {
  84         private final Sequence s;
  85         private final HashSet<Sequence> eq = new HashSet<Sequence>();
  86         public final HashSet<Sequence> walk() { return walk(s); }
  87         public EquivalentTo(Sequence e, Cache c)  {
  88             super(c); this.s = e;
  89         }
  90         public HashSet<Sequence> bottom(SequenceOrElement e)     { return eq; }
  91         public HashSet<Sequence> walkSequence(Sequence seq) {
  92             eq.add(seq);
  93             Position p = seq.firstp();
  94             for(; !p.isLast(); p = p.next()) {
  95                 if (!p.isLast() && isRightNullable(p.next()))
  96                     walk(p.element());
  97                 if (!c.possiblyEpsilon(p.element())) break;
  98             }
  99             return eq;
 100         }
 101         public HashSet<Sequence> walkAtom(Atom r) {
 102             return eq;
 103         }
 104         private boolean isRightNullable(Position p) {
 105             if (p.isLast()) return true;
 106             if (!c.possiblyEpsilon(p.element())) return false;
 107             return isRightNullable(p.next());
 108         }
 109     }
 110
 111
 112     // Boolean //////////////////////////////////////////////////////////////////////////////
 113
 114     static class PossiblyEpsilon extends Walk<Boolean> {
 115         public Boolean walkAtom(Atom r) { return false; }
 116         public Boolean sequence(Sequence s, Boolean a, Boolean b)  { return new Boolean(a && b); }
 117         public Boolean union(Union u, Boolean a, Boolean b)     { return new Boolean(a || b); }
 118         public Boolean bottom(SequenceOrElement e)    { return (e instanceof Union) ? false : true; }
 119         private HashMap<SequenceOrElement,Boolean> hm = new HashMap<SequenceOrElement,Boolean>();
 120         protected Boolean walk(SequenceOrElement e) {
 121             if (hm.get(e) != null) return hm.get(e);
 122             hm.put(e, false);
 123             Boolean ret = walk2(e);
 124             hm.put(e, ret);
 125             return ret;
 126         }
 127     }
 128
 129     static class EpsilonFollowSet extends Walk<Atom> {
 130         Atom all;
 131         Atom empty;
 132         public EpsilonFollowSet(Atom a, Atom empty, Cache c) {
 133             super(c);
 134             this.all = all;
 135             this.empty = empty;
 136         }
 137         public Atom walkAtom(Atom r) { return all; }
 138         public Atom walkSequence(Sequence s) {
 139             if (s.follow==null) return all;
 140             return s.follow;
 141         }
 142         public Atom sequence(Sequence s, Atom a, Atom b)  {
 143             throw new RuntimeException();
 144         }
 145         public Atom union(Union u, Atom a, Atom b) {
 146             /*
 147             if (a==null) return b;
 148             if (b==null) return a;
 149             */
 150             if (a==null || b==null) return all;
 151             return (Atom)a.union(b);
 152         }
 153         public Atom bottom(SequenceOrElement e) {
 154             return (e instanceof Union) ? empty : all;
 155         }
 156     }
 157
 158     // Input-Set //////////////////////////////////////////////////////////////////////////////
 159
 160     static abstract class WalkTokenSet<Tok extends Input> extends Walk<Topology<Tok>> {
 161         public Topology<Tok> cs;
 162         public WalkTokenSet(Topology<Tok> cs)          { this.cs = cs; }
 163         public WalkTokenSet(Topology<Tok> cs, Cache c) { super(c); this.cs = cs; }
 164         public Topology<Tok> bottom(SequenceOrElement e)         { return cs; }
 165         public Topology<Tok> walkAtom(Atom r)          { cs = cs.union(r.getTokenTopology()); return cs; }
 166     }
 167
 168     // feature: intersect with "first" set of all positive conjuncts
 169     static class First<Tok extends Input> extends WalkTokenSet<Tok> {
 170         public First(Topology<Tok> cs, Walk.Cache cache) { super(cs, cache); }
 171         public Topology<Tok> walkSequence(Sequence seq) {
 172             for(Position p = seq.firstp(); p!=null && !p.isLast(); p = p.next()) {
 173                 walk(p.element());
 174                 if (!c.possiblyEpsilon(p.element())) break;
 175             }
 176             return cs;
 177         }
 178     }
 179
 180     static class Follow<Tok extends Input> extends WalkTokenSet<Tok> {
 181         private final SequenceOrElement me;
 182         private final HashSet<SequenceOrElement> all;
 183         private boolean eof = false;
 184         public boolean includesEof() { return eof; }
 185         public Follow(Topology<Tok> cs, SequenceOrElement me, HashSet<SequenceOrElement> all, Cache c)  {
 186           super(cs, c); this.me = me; this.all = all; }
 187         public Topology<Tok> bottom(SequenceOrElement e)                       { return cs; }
 188         public Topology<Tok> walkSequence(Sequence seq)                  { return cs; }
 189         public Topology<Tok> walkAtom(Atom r) { return walk((SequenceOrElement)r); }
 190         public Topology<Tok> walk(SequenceOrElement e) {
 191             if (acc.contains(e)) return bottom(e);
 192             acc.add(e);
 193
 194             if (c != null) {
 195                 Topology<Tok> cached = (Topology<Tok>)c.follow.get(e);
 196                 if (cached != null) {
 197                     cs = cs.union(cached);
 198                     eof |= c.eof.get(e);
 199                     return cs;
 200                 }
 201             }
 202
 203             Topology<Tok> cso = cs;
 204             boolean eofo = eof;
 205             eof = c.eof.get(e) != null && c.eof.get(e).booleanValue();
 206             cs = cso.empty();
 207
 208             for(SequenceOrElement x : all) {
 209                 boolean matched = false;
 210                 if (!(x instanceof Sequence)) continue;
 211                 Sequence a = (Sequence)x;
 212                 Position mp = null;
 213                 for(Position pos = a.firstp(); pos != null && !pos.isLast(); pos = pos.next()) {
 214                     if (matched) cs = cs.union(c.first(pos.element(), cs.empty()));
 215                     if (pos.isLast()) { matched = (matched && c.possiblyEpsilon(pos.element())); continue; }
 216                     boolean good = false;
 217                     if (e instanceof Atom) {
 218                         Topology top = c.atoms.get(pos.element());
 219                         if (top==null) continue;
 220                         if (!(top.containsAll(((Atom)e)))) continue;
 221                     } else {
 222                         if (c.ys.contains(pos.element(),e)) good = true;
 223                     }
 224                     if (good) {
 225                         mp = pos;
 226                         matched = true;
 227                     }
 228                 }
 229                 if (matched) walk(a);
 230             }
 231
 232             if (e instanceof Sequence) {
 233                 Sequence s = (Sequence)e;
 234                 if (s.follow != null) cs = cs.intersect(s.follow.getTokenTopology());
 235             }
 236
 237             if (c != null && e==me) {
 238                 c.follow.put(e, cs);
 239                 c.eof.put(e, eof);
 240             }
 241
 242             cso = cso.union(cs);
 243             cs = cso;
 244             eofo |= eof;
 245             eof = eofo;
 246
 247             return cs;
 248         }
 249     }
 250
 251     static class Cache {
 252         public final HashMap<SequenceOrElement,Boolean> possiblyEpsilon = new HashMap<SequenceOrElement,Boolean>();
 253         public HashMap<SequenceOrElement,Boolean> eof = new HashMap<SequenceOrElement,Boolean>();
 254         public HashMap<SequenceOrElement,Topology> follow = new HashMap<SequenceOrElement,Topology>();
 255         public HashMapBag<SequenceOrElement,SequenceOrElement>  ys = new HashMapBag<SequenceOrElement,SequenceOrElement>();
 256         public HashMapBag<SequenceOrElement,SequenceOrElement>  ys2 = new HashMapBag<SequenceOrElement,SequenceOrElement>();
 257         public HashMap<SequenceOrElement,Topology> atoms = new HashMap<SequenceOrElement,Topology>();
 258         public <Tok extends Input> Topology<Tok> first(SequenceOrElement e, Topology<Tok> empty) {
 259             return new Walk.First<Tok>(empty, this).walk(e);
 260         }
 261         final boolean possiblyEpsilon(SequenceOrElement e) {
 262             Walk.Cache cache = this;
 263             Boolean ret = possiblyEpsilon.get(e);
 264             if (ret != null) return ret.booleanValue();
 265             ret = new Walk.PossiblyEpsilon().walk(e) ? Boolean.TRUE : Boolean.FALSE;
 266             possiblyEpsilon.put(e, ret);
 267             return ret;
 268         }
 269     }
 270 }