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
  45                 // FIXME
  46                 for(Sequence ss : s.needs()) ret = union((Union)e, ret, walk(ss));
  47                 for(Sequence ss : s.hates()) ret = union((Union)e, ret, walk(ss));
  48             }
  49             return ret;
  50         } else {
  51             throw new Error("unknown element of class " + e.getClass().getName() + ": " + e);
  52         }
  53     }
  54
  55     static class YieldSet extends Walk<HashSet<SequenceOrElement>> {
  56         private final SequenceOrElement e;
  57         public final HashSet<SequenceOrElement> walk() { return walk(e); }
  58         public YieldSet(SequenceOrElement e, Cache c)  { super(c); this.e = e; }
  59         public HashSet<SequenceOrElement> bottom(SequenceOrElement e)     { return acc; }
  60         public HashSet<SequenceOrElement> walkSequence(Sequence seq) { return bottom(seq); }
  61         public HashSet<SequenceOrElement> walkAtom(Atom r) {
  62             c.atoms.put(e, c.atoms.get(e)==null ? r : c.atoms.get(e).union(r));
  63             return super.walkAtom(r);
  64         }
  65     }
  66
  67     static class EquivalentTo extends Walk<HashSet<Sequence>> {
  68         private final Sequence s;
  69         private final HashSet<Sequence> eq = new HashSet<Sequence>();
  70         public final HashSet<Sequence> walk() { return walk(s); }
  71         public EquivalentTo(Sequence e, Cache c)  {
  72             super(c); this.s = e;
  73         }
  74         public HashSet<Sequence> bottom(SequenceOrElement e)     { return eq; }
  75         public HashSet<Sequence> walkSequence(Sequence seq) {
  76             eq.add(seq);
  77             Position p = seq.firstp();
  78             for(; !p.isLast(); p = p.next()) {
  79                 if (!p.isLast() && isRightNullable(p.next()))
  80                     walk(p.element());
  81                 if (!c.possiblyEpsilon(p.element())) break;
  82             }
  83             return eq;
  84         }
  85         public HashSet<Sequence> walkAtom(Atom r) {
  86             return eq;
  87         }
  88         private boolean isRightNullable(Position p) {
  89             if (p.isLast()) return true;
  90             if (!c.possiblyEpsilon(p.element())) return false;
  91             return isRightNullable(p.next());
  92         }
  93     }
  94
  95
  96     // Boolean //////////////////////////////////////////////////////////////////////////////
  97
  98     static class PossiblyEpsilon extends Walk<Boolean> {
  99         public Boolean walkAtom(Atom r) { return false; }
 100         public Boolean sequence(Sequence s, Boolean a, Boolean b)  { return new Boolean(a && b); }
 101         public Boolean union(Union u, Boolean a, Boolean b)     { return new Boolean(a || b); }
 102         public Boolean bottom(SequenceOrElement e)    { return (e instanceof Union) ? false : true; }
 103         private HashMap<SequenceOrElement,Boolean> hm = new HashMap<SequenceOrElement,Boolean>();
 104         protected Boolean walk(SequenceOrElement e) {
 105             if (hm.get(e) != null) return hm.get(e);
 106             hm.put(e, false);
 107             Boolean ret = walk2(e);
 108             hm.put(e, ret);
 109             return ret;
 110         }
 111     }
 112
 113     static class EpsilonFollowSet extends Walk<Atom> {
 114         Atom all;
 115         Atom empty;
 116         public EpsilonFollowSet(Atom a, Atom empty, Cache c) {
 117             super(c);
 118             this.all = all;
 119             this.empty = empty;
 120         }
 121         public Atom walkAtom(Atom r) { return all; }
 122         public Atom walkSequence(Sequence s) {
 123             if (s.follow==null) return all;
 124             return s.follow;
 125         }
 126         public Atom sequence(Sequence s, Atom a, Atom b)  {
 127             throw new RuntimeException();
 128         }
 129         public Atom union(Union u, Atom a, Atom b) {
 130             /*
 131             if (a==null) return b;
 132             if (b==null) return a;
 133             */
 134             if (a==null || b==null) return all;
 135             return (Atom)a.union(b);
 136         }
 137         public Atom bottom(SequenceOrElement e) {
 138             return (e instanceof Union) ? empty : all;
 139         }
 140     }
 141
 142     // Input-Set //////////////////////////////////////////////////////////////////////////////
 143
 144     static abstract class WalkTokenSet<Tok extends Input> extends Walk<Topology<Tok>> {
 145         public Topology<Tok> cs;
 146         public WalkTokenSet(Topology<Tok> cs)          { this.cs = cs; }
 147         public WalkTokenSet(Topology<Tok> cs, Cache c) { super(c); this.cs = cs; }
 148         public Topology<Tok> bottom(SequenceOrElement e)         { return cs; }
 149         public Topology<Tok> walkAtom(Atom r)          { cs = cs.union(r.getTokenTopology()); return cs; }
 150     }
 151
 152     static class First<Tok extends Input> extends WalkTokenSet<Tok> {
 153         public First(Topology<Tok> cs, Walk.Cache cache) { super(cs, cache); }
 154         public Topology<Tok> walkSequence(Sequence seq) {
 155             for(Position p = seq.firstp(); p!=null && !p.isLast(); p = p.next()) {
 156                 walk(p.element());
 157                 if (!c.possiblyEpsilon(p.element())) break;
 158             }
 159             return cs;
 160         }
 161     }
 162
 163     static class Follow<Tok extends Input> extends WalkTokenSet<Tok> {
 164         private final SequenceOrElement me;
 165         private final HashSet<SequenceOrElement> all;
 166         private boolean eof = false;
 167         public boolean includesEof() { return eof; }
 168         public Follow(Topology<Tok> cs, SequenceOrElement me, HashSet<SequenceOrElement> all, Cache c)  {
 169           super(cs, c); this.me = me; this.all = all; }
 170         public Topology<Tok> bottom(SequenceOrElement e)                       { return cs; }
 171         public Topology<Tok> walkSequence(Sequence seq)                  { return cs; }
 172         public Topology<Tok> walkAtom(Atom r) { return walk((SequenceOrElement)r); }
 173         public Topology<Tok> walk(SequenceOrElement e) {
 174             if (acc.contains(e)) return bottom(e);
 175             acc.add(e);
 176
 177             if (c != null) {
 178                 Topology<Tok> cached = (Topology<Tok>)c.follow.get(e);
 179                 if (cached != null) {
 180                     cs = cs.union(cached);
 181                     eof |= c.eof.get(e);
 182                     return cs;
 183                 }
 184             }
 185
 186             Topology<Tok> cso = cs;
 187             boolean eofo = eof;
 188             eof = c.eof.get(e) != null && c.eof.get(e).booleanValue();
 189             cs = cso.empty();
 190
 191             for(SequenceOrElement x : all) {
 192                 boolean matched = false;
 193                 if (!(x instanceof Sequence)) continue;
 194                 Sequence a = (Sequence)x;
 195                 Position mp = null;
 196                 for(Position pos = a.firstp(); pos != null && !pos.isLast(); pos = pos.next()) {
 197                     if (matched) cs = cs.union(c.first(pos.element(), cs.empty()));
 198                     if (pos.isLast()) { matched = (matched && c.possiblyEpsilon(pos.element())); continue; }
 199                     boolean good = false;
 200                     if (e instanceof Atom) {
 201                         Topology top = c.atoms.get(pos.element());
 202                         if (top==null) continue;
 203                         if (!(top.containsAll(((Atom)e)))) continue;
 204                     } else {
 205                         if (c.ys.contains(pos.element(),e)) good = true;
 206                     }
 207                     if (good) {
 208                         mp = pos;
 209                         matched = true;
 210                     }
 211                 }
 212                 if (matched) walk(a);
 213             }
 214
 215             if (e instanceof Sequence) {
 216                 Sequence s = (Sequence)e;
 217                 if (s.follow != null) cs = cs.intersect(s.follow.getTokenTopology());
 218             }
 219
 220             if (c != null && e==me) {
 221                 c.follow.put(e, cs);
 222                 c.eof.put(e, eof);
 223             }
 224
 225             cso = cso.union(cs);
 226             cs = cso;
 227             eofo |= eof;
 228             eof = eofo;
 229
 230             return cs;
 231         }
 232     }
 233
 234     static class Cache {
 235         public final HashMap<SequenceOrElement,Boolean> possiblyEpsilon = new HashMap<SequenceOrElement,Boolean>();
 236         public HashMap<SequenceOrElement,Boolean> eof = new HashMap<SequenceOrElement,Boolean>();
 237         public HashMap<SequenceOrElement,Topology> follow = new HashMap<SequenceOrElement,Topology>();
 238         public HashMapBag<SequenceOrElement,SequenceOrElement>  ys = new HashMapBag<SequenceOrElement,SequenceOrElement>();
 239         public HashMap<SequenceOrElement,Topology> atoms = new HashMap<SequenceOrElement,Topology>();
 240         public <Tok extends Input> Topology<Tok> first(SequenceOrElement e, Topology<Tok> empty) {
 241             return new Walk.First<Tok>(empty, this).walk(e);
 242         }
 243         final boolean possiblyEpsilon(SequenceOrElement e) {
 244             Walk.Cache cache = this;
 245             Boolean ret = possiblyEpsilon.get(e);
 246             if (ret != null) return ret.booleanValue();
 247             ret = new Walk.PossiblyEpsilon().walk(e) ? Boolean.TRUE : Boolean.FALSE;
 248             possiblyEpsilon.put(e, ret);
 249             return ret;
 250         }
 251     }
 252 }