src/edu/berkeley/sbp/Parser.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
  10 /** a parser which translates an Input&lt;Token&gt; into a Forest&lt;NodeType&gt; */
  11 public abstract class Parser<Token, NodeType> {
  12
  13     protected final Table<Token> pt;
  14
  15     /** create a parser to parse the grammar with start symbol <tt>u</tt> */
  16     public Parser(Union u, Topology<Token> top)  { this.pt = new Table<Token>(u, top); }
  17
  18     /** implement this method to create the output forest corresponding to a lone shifted input token */
  19     public abstract Forest<NodeType> shiftToken(Token t, Input.Location newloc);
  20
  21     public String toString() { return pt.toString(); }
  22
  23     private boolean verbose = false;;
  24     private static final char[] spin = new char[] { '-', '\\', '|', '/' };
  25     private int spinpos = 0;
  26     private long last = 0;
  27     void spin() {
  28         if (verbose) {
  29             long now = System.currentTimeMillis();
  30             if (now-last < 70) return;
  31             last = now;
  32             System.err.print("\r  " + spin[spinpos++ % (spin.length)]+ANSI.clreol()+"\r");
  33         }
  34     }
  35
  36     /** parse <tt>input</tt>, and return the shared packed parse forest (or throw an exception) */
  37     public Forest<NodeType> parse(Input<Token> input) throws IOException, ParseFailed {
  38         verbose = System.getProperty("sbp.verbose", null) != null;
  39         spinpos = 0;
  40         try {
  41             GSS gss = new GSS(input, this);
  42             for(GSS.Phase current = gss.new Phase<Token>(pt.start); ;) {
  43
  44                 if (verbose) {
  45                     String s;
  46                     s = "  " + spin[spinpos++ % (spin.length)]+" parsing ";
  47                     s += input.getName();
  48                     s += " "+input.getLocation();
  49                     while(s.indexOf(':') != -1 && s.indexOf(':') < 8) s = " " + s;
  50                     String y = "@"+gss.viewPos+" ";
  51                     while(y.length() < 9) y = " " + y;
  52                     s += y;
  53                     //s += "   doom="+Node.doomedNodes;
  54                     //while(s.length() < 40) s = s + " ";
  55                     s += "   nodes="+gss.numOldNodes;
  56                     while(s.length() < 50) s = s + " ";
  57                     s += " shifted="+gss.numNewNodes;
  58                     while(s.length() < 60) s = s + " ";
  59                     s += " reductions="+gss.numReductions;
  60                     System.err.print("\r"+s+ANSI.clreol()+"\r");
  61                 }
  62
  63                 // FIXME: make sure all the locations line up properly in here
  64                 if (current.isDone()) return (Forest<NodeType>)current.finalResult;
  65                 Forest forest = shiftToken((Token)current.token, input.getLocation());
  66                 current = gss.new Phase<Token>(current, forest);
  67             }
  68         } finally {
  69             if (verbose)
  70                 System.err.print("\r                                                                                \r");
  71         }
  72     }
  73
  74
  75     // Table //////////////////////////////////////////////////////////////////////////////
  76
  77     /** an SLR(1) parse table which may contain conflicts */
  78     static class Table<Token> extends Cache {
  79
  80         /** the start state */
  81         public  final State<Token>   start;
  82
  83         /** the state from which no reductions can be done */
  84         private final State<Token>   dead_state;
  85
  86         /** used to generate unique values for State.idx */
  87         private int master_state_idx = 0;
  88         HashSet<State<Token>>   all_states    = new HashSet<State<Token>>();
  89         HashMap<HashSet<Position>,State<Token>>   doomed_states    = new HashMap<HashSet<Position>,State<Token>>();
  90         HashMap<HashSet<Position>,State<Token>>   normal_states    = new HashMap<HashSet<Position>,State<Token>>();
  91
  92         /** construct a parse table for the given grammar */
  93         public Table(Topology top) { this("s", top); }
  94         public Table(String startSymbol, Topology top) { this(new Union(startSymbol), top); }
  95         public Table(Union ux, Topology top) {
  96             super(ux, top);
  97             Union start0 = new Union("0");
  98             Sequence seq0 = new Sequence.Singleton(ux);
  99             start0.add(seq0);
 100             buildFollowSet(seq0, top, true);
 101
 102             // construct the set of states
 103             HashSet<Position> hp = new HashSet<Position>();
 104             reachable(start0, hp);
 105
 106             this.dead_state = new State<Token>(new HashSet<Position>(), true);
 107             this.start = new State<Token>(hp);
 108
 109             // for each state, fill in the corresponding "row" of the parse table
 110             for(State<Token> state : all_states)
 111                 for(Position p : state.hs) {
 112
 113                     // the Grammar's designated "last position" is the only accepting state
 114                     if (start0.contains(p.owner()) && p.next()==null && !state.doomed)
 115                         state.accept = true;
 116
 117                     if (isRightNullable(p)) {
 118                         Topology<Token> follow = (Topology<Token>)follow(p.owner());
 119                         for(Position p2 = p; p2 != null && p2.element() != null; p2 = p2.next()) {
 120                             if (!(p2.element() instanceof Union)) throw new Error("impossible");
 121                             Union u = (Union)p2.element();
 122                             Atom set = new edu.berkeley.sbp.chr.CharAtom(new edu.berkeley.sbp.chr.CharTopology((Topology<Character>)epsilonFollowSet(u)));
 123                             Element p2e = p2.element();
 124                             if (p2e instanceof Union)
 125                                 for(Sequence p2es : ((Union)p2e))
 126                                     follow = follow.intersect(follow(p2es));
 127                             if (set != null) follow = follow.intersect(set.getTokenTopology());
 128                         }
 129                         state.reductions.put(follow, p);
 130                         if (followEof.contains(p.owner())) state.eofReductions.add(p);
 131                     }
 132
 133                     // if the element following this position is an atom, copy the corresponding
 134                     // set of rows out of the "master" goto table and into this state's shift table
 135                     if (p.element() != null && p.element() instanceof Atom)
 136                         state.shifts.addAll(state.gotoSetTerminals.subset(((Atom)p.element()).getTokenTopology()));
 137                 }
 138
 139             if (top instanceof IntegerTopology)
 140                 for(State<Token> state : all_states) {
 141                     state.oreductions = state.reductions.optimize(((IntegerTopology)top).functor());
 142                     state.oshifts = state.shifts.optimize(((IntegerTopology)top).functor());
 143                 }
 144
 145             // crude algorithm to assing an ordinal ordering to every position
 146             // al will be sorted in DECREASING order (al[0] >= al[1])
 147             ArrayList<Sequence.Position> al = new ArrayList<Sequence.Position>();
 148             for(State s : all_states) {
 149                 for(Object po : s) {
 150                     Sequence.Position p = (Sequence.Position)po;
 151                     if (al.contains(p)) continue;
 152                     int i=0;
 153                     for(; i<al.size(); i++) {
 154                         if (comparePositions(p, al.get(i)) < 0)
 155                             break;
 156                     }
 157                     al.add(i, p);
 158                 }
 159             }
 160             // FIXME: this actually pollutes the "pure" objects (the ones that should not be modified by the Parser)
 161             // sort in increasing order...
 162             OUTER: while(true) {
 163                 for(int i=0; i<al.size(); i++)
 164                     for(int j=i+1; j<al.size(); j++)
 165                         if (comparePositions(al.get(i), al.get(j)) > 0) {
 166                             Sequence.Position p = al.remove(j);
 167                             al.add(i, p);
 168                             continue OUTER;
 169                         }
 170                 break;
 171             }
 172
 173             int j = 1;
 174             int pk = 0;
 175             for(int i=0; i<al.size(); i++) {
 176                 boolean inc = false;
 177                 for(int k=pk; k<i; k++) {
 178                     if (comparePositions(al.get(k), al.get(i)) > 0)
 179                         { inc = true; break; }
 180                 }
 181                 inc = true;
 182                 if (inc) {
 183                     j++;
 184                     pk = i;
 185                 }
 186                 al.get(i).ord = j;
 187             }
 188
 189             /*
 190             for(int i=0; i<al.size(); i++)
 191                 if (isRightNullable(al.get(i)))
 192                     System.out.println(al.get(i).ord + "   " + al.get(i));
 193             */
 194             //mastercache = this;
 195         }
 196
 197         /** a single state in the LR table and the transitions possible from it */
 198         class State<Token> implements IntegerMappable, Iterable<Position> {
 199
 200             public  final     int               idx    = master_state_idx++;
 201             private final     HashSet<Position> hs;
 202             public HashSet<State<Token>> also = new HashSet<State<Token>>();
 203
 204             public  transient HashMap<Sequence,State<Token>>         gotoSetNonTerminals = new HashMap<Sequence,State<Token>>();
 205             private transient TopologicalBag<Token,State<Token>>     gotoSetTerminals    = new TopologicalBag<Token,State<Token>>();
 206
 207             private           TopologicalBag<Token,Position>      reductions          = new TopologicalBag<Token,Position>();
 208             private           HashSet<Position>                   eofReductions       = new HashSet<Position>();
 209             private           TopologicalBag<Token,State<Token>>  shifts              = new TopologicalBag<Token,State<Token>>();
 210             private           boolean                             accept              = false;
 211
 212             private VisitableMap<Token,State<Token>> oshifts     = null;
 213             private VisitableMap<Token,Position>     oreductions = null;
 214
 215             // Interface Methods //////////////////////////////////////////////////////////////////////////////
 216
 217             boolean                    isAccepting()           { return accept; }
 218             public Iterator<Position>  iterator()              { return hs.iterator(); }
 219             boolean                    canShift(Token t)       { return oshifts!=null && oshifts.contains(t); }
 220             void                       invokeShifts(Token t, GSS.Phase phase, Result r) { oshifts.invoke(t, phase, r); }
 221             boolean                    canReduce(Token t)        {
 222                 return oreductions != null && (t==null ? eofReductions.size()>0 : oreductions.contains(t)); }
 223             void          invokeEpsilonReductions(Token t, Node node) {
 224                 if (t==null) for(Position r : eofReductions) node.invoke(r, null);
 225                 else         oreductions.invoke(t, node, null);
 226             }
 227             void          invokeReductions(Token t, Node node, Result b) {
 228                 //System.err.println("\rinvokage:  " + this);
 229                 if (t==null) for(Position r : eofReductions) node.invoke(r, b);
 230                 else         oreductions.invoke(t, node, b);
 231             }
 232
 233             // Constructor //////////////////////////////////////////////////////////////////////////////
 234
 235             /**
 236              *  create a new state consisting of all the <tt>Position</tt>s in <tt>hs</tt>
 237              *  @param hs           the set of <tt>Position</tt>s comprising this <tt>State</tt>
 238              *  @param all the set of all elements (Atom instances need not be included)
 239              *
 240              *   In principle these two steps could be merged, but they
 241              *   are written separately to highlight these two facts:
 242              * <ul>
 243              * <li> Non-atom elements either match all-or-nothing, and do not overlap
 244              *      with each other (at least not in the sense of which element corresponds
 245              *      to the last reduction performed).  Therefore, in order to make sure we
 246              *      wind up with the smallest number of states and shifts, we wait until
 247              *      we've figured out all the token-to-position multimappings before creating
 248              *      any new states
 249              *
 250              * <li> In order to be able to run the state-construction algorithm in a single
 251              *      shot (rather than repeating until no new items appear in any state set),
 252              *      we need to use the "yields" semantics rather than the "produces" semantics
 253              *      for non-Atom Elements.
 254              *  </ul>
 255              */
 256             public State(HashSet<Position> hs) { this(hs, false); }
 257             public boolean doomed;
 258             public State(HashSet<Position> hs, boolean doomed) {
 259                 this.hs = hs;
 260                 this.doomed = doomed;
 261
 262                 // register ourselves in the all_states hash so that no
 263                 // two states are ever created with an identical position set
 264                 ((HashMap)(doomed ? doomed_states : normal_states)).put(hs, this);
 265                 ((HashSet)all_states).add(this);
 266
 267                 for(Position p : hs) {
 268                     if (!p.isFirst()) continue;
 269                     for(Sequence s : p.owner().needs()) {
 270                         if (hs.contains(s.firstp())) continue;
 271                         HashSet<Position> h2 = new HashSet<Position>();
 272                         reachable(s, h2);
 273                         also.add(mkstate(h2, true));
 274                     }
 275                     for(Sequence s : p.owner().hates()) {
 276                         if (hs.contains(s.firstp())) continue;
 277                         HashSet<Position> h2 = new HashSet<Position>();
 278                         reachable(s, h2);
 279                         also.add(mkstate(h2, true));
 280                     }
 281                 }
 282
 283                 // Step 1a: examine all Position's in this state and compute the mappings from
 284                 //          sets of follow tokens (tokens which could follow this position) to sets
 285                 //          of _new_ positions (positions after shifting).  These mappings are
 286                 //          collectively known as the _closure_
 287
 288                 TopologicalBag<Token,Position> bag0 = new TopologicalBag<Token,Position>();
 289                 for(Position position : hs) {
 290                     if (position.isLast() || !(position.element() instanceof Atom)) continue;
 291                     Atom a = (Atom)position.element();
 292                     HashSet<Position> hp = new HashSet<Position>();
 293                     reachable(position.next(), hp);
 294                     bag0.addAll(a.getTokenTopology(), hp);
 295                 }
 296
 297                 // Step 1b: for each _minimal, contiguous_ set of characters having an identical next-position
 298                 //          set, add that character set to the goto table (with the State corresponding to the
 299                 //          computed next-position set).
 300
 301                 for(Topology<Token> r : bag0) {
 302                     HashSet<Position> h = new HashSet<Position>();
 303                     for(Position p : bag0.getAll(r)) h.add(p);
 304                     ((TopologicalBag)gotoSetTerminals).put(r, mkstate(h, doomed));
 305                 }
 306
 307                 // Step 2: for every Sequence, compute the closure over every position in this set which
 308                 //         is followed by a symbol which could yield the Sequence.
 309                 //
 310                 //         "yields" [in one or more step] is used instead of "produces" [in exactly one step]
 311                 //         to avoid having to iteratively construct our set of States as shown in most
 312                 //         expositions of the algorithm (ie "keep doing XYZ until things stop changing").
 313
 314                 HashMapBag<Sequence,Position> move = new HashMapBag<Sequence,Position>();
 315                 for(Position p : hs)
 316                     if (!p.isLast() && p.element() instanceof Union)
 317                         for(Sequence s : ((Union)p.element())) {
 318                             HashSet<Position> hp = new HashSet<Position>();
 319                             reachable(p.next(), hp);
 320                             move.addAll(s, hp);
 321                         }
 322                 OUTER: for(Sequence y : move) {
 323                     // if a reduction is "lame", it should wind up in the dead_state after reducing
 324                     HashSet<Position> h = move.getAll(y);
 325                     State<Token> s = mkstate(h, doomed);
 326                     for(Position p : hs)
 327                         if (p.element() != null && (p.element() instanceof Union))
 328                             for(Sequence seq : ((Union)p.element()))
 329                                 if (seq.needs.contains(y) || seq.hates.contains(y)) {
 330                                     // FIXME: assumption that no sequence is ever both usefully (non-lamely) matched
 331                                     //        and also directly lamely matched
 332                                     ((HashMap)gotoSetNonTerminals).put(y, dead_state);
 333                                     continue OUTER;
 334                                 }
 335                     gotoSetNonTerminals.put(y, s);
 336                 }
 337             }
 338
 339             private State<Token> mkstate(HashSet<Position> h, boolean b) {
 340                 if (b) return doomed_states.get(h) == null ? (State)new State<Token>(h,b) : (State)doomed_states.get(h);
 341                 else   return normal_states.get(h) == null ? (State)new State<Token>(h,b) : (State)normal_states.get(h);
 342             }
 343
 344             public String toStringx() {
 345                 StringBuffer st = new StringBuffer();
 346                 for(Position p : this) {
 347                     if (st.length() > 0) st.append("\n");
 348                     st.append(p);
 349                 }
 350                 return st.toString();
 351             }
 352
 353             public String toString() {
 354                 StringBuffer ret = new StringBuffer();
 355                 ret.append("state["+idx+"]: ");
 356                 for(Position p : this) ret.append("{"+p+"}  ");
 357                 return ret.toString();
 358             }
 359
 360             public int toInt() { return idx; }
 361         }
 362
 363         public String toString() {
 364             StringBuffer sb = new StringBuffer();
 365             sb.append("parse table");
 366             for(State<Token> state : all_states) {
 367                 sb.append("  " + state + "\n");
 368                 for(Topology<Token> t : state.shifts) {
 369                     sb.append("      shift  \""+
 370                               new edu.berkeley.sbp.chr.CharTopology((IntegerTopology<Character>)t)+"\" => ");
 371                     for(State st : state.shifts.getAll(t))
 372                         sb.append(st.idx+"  ");
 373                     sb.append("\n");
 374                 }
 375                 for(Topology<Token> t : state.reductions)
 376                     sb.append("      reduce \""+
 377                               new edu.berkeley.sbp.chr.CharTopology((IntegerTopology<Character>)t)+"\" => " +
 378                               state.reductions.getAll(t) + "\n");
 379                 for(Sequence s : state.gotoSetNonTerminals.keySet())
 380                     sb.append("      goto   "+state.gotoSetNonTerminals.get(s)+" from " + s + "\n");
 381             }
 382             return sb.toString();
 383         }
 384     }
 385
 386     // Helpers //////////////////////////////////////////////////////////////////////////////
 387
 388     private static void reachable(Sequence s, HashSet<Position> h) {
 389         reachable(s.firstp(), h);
 390         //for(Sequence ss : s.needs()) reachable(ss, h);
 391         //for(Sequence ss : s.hates()) reachable(ss, h);
 392     }
 393     private static void reachable(Element e, HashSet<Position> h) {
 394         if (e instanceof Atom) return;
 395         for(Sequence s : ((Union)e))
 396             reachable(s, h);
 397     }
 398     private static void reachable(Position p, HashSet<Position> h) {
 399         if (h.contains(p)) return;
 400         h.add(p);
 401         if (p.element() != null) reachable(p.element(), h);
 402     }
 403     //public static Cache mastercache = null;
 404 }