src/theory/theory.h

   1 /*********************                                                        */
   2 /*! \file theory.h
   3  ** \verbatim
   4  ** Original author: Morgan Deters
   5  ** Major contributors: Tim King, Dejan Jovanovic
   6  ** Minor contributors (to current version): Francois Bobot, Kshitij Bansal, Martin Brain <>, Clark Barrett, Andrew Reynolds
   7  ** This file is part of the CVC4 project.
   8  ** Copyright (c) 2009-2014  New York University and The University of Iowa
   9  ** See the file COPYING in the top-level source directory for licensing
  10  ** information.\endverbatim
  11  **
  12  ** \brief Base of the theory interface.
  13  **
  14  ** Base of the theory interface.
  15  **/
  16
  17 #include "cvc4_private.h"
  18
  19 #ifndef __CVC4__THEORY__THEORY_H
  20 #define __CVC4__THEORY__THEORY_H
  21
  22 #include "expr/node.h"
  23 //#include "expr/attribute.h"
  24 #include "expr/command.h"
  25 #include "smt/logic_request.h"
  26 #include "theory/valuation.h"
  27 #include "theory/output_channel.h"
  28 #include "theory/logic_info.h"
  29 #include "theory/options.h"
  30 #include "theory/theoryof_mode.h"
  31 #include "context/context.h"
  32 #include "context/cdlist.h"
  33 #include "context/cdo.h"
  34 #include "options/options.h"
  35 #include "util/statistics_registry.h"
  36 #include "util/dump.h"
  37 #include "lib/ffs.h"
  38
  39 #include <string>
  40 #include <iostream>
  41
  42 #include <strings.h>
  43 #include <ext/hash_set>
  44
  45 namespace CVC4 {
  46
  47 class TheoryEngine;
  48
  49 namespace theory {
  50
  51 class QuantifiersEngine;
  52 class TheoryModel;
  53 class SubstitutionMap;
  54
  55 class EntailmentCheckParameters;
  56 class EntailmentCheckSideEffects;
  57
  58 namespace rrinst {
  59   class CandidateGenerator;
  60 }/* CVC4::theory::rrinst namespace */
  61
  62 namespace eq {
  63   class EqualityEngine;
  64 }/* CVC4::theory::eq namespace */
  65
  66 /**
  67  * Information about an assertion for the theories.
  68  */
  69 struct Assertion {
  70
  71   /** The assertion */
  72   Node assertion;
  73   /** Has this assertion been preregistered with this theory */
  74   bool isPreregistered;
  75
  76   Assertion(TNode assertion, bool isPreregistered)
  77   : assertion(assertion), isPreregistered(isPreregistered) {}
  78
  79   /**
  80    * Convert the assertion to a TNode.
  81    */
  82   operator TNode () const {
  83     return assertion;
  84   }
  85
  86   /**
  87    * Convert the assertion to a Node.
  88    */
  89   operator Node () const {
  90     return assertion;
  91   }
  92
  93 };/* struct Assertion */
  94
  95 /**
  96  * A (oredered) pair of terms a theory cares about.
  97  */
  98 struct CarePair {
  99
 100   TNode a, b;
 101   TheoryId theory;
 102
 103 public:
 104
 105   CarePair(TNode a, TNode b, TheoryId theory)
 106   : a(a < b ? a : b), b(a < b ? b : a), theory(theory) {}
 107
 108   bool operator == (const CarePair& other) const {
 109     return (theory == other.theory) && (a == other.a) && (b == other.b);
 110   }
 111
 112   bool operator < (const CarePair& other) const {
 113     if (theory < other.theory) return true;
 114     if (theory > other.theory) return false;
 115     if (a < other.a) return true;
 116     if (a > other.a) return false;
 117     return b < other.b;
 118   }
 119
 120 };/* struct CarePair */
 121
 122 /**
 123  * A set of care pairs.
 124  */
 125 typedef std::set<CarePair> CareGraph;
 126
 127 /**
 128  * Base class for T-solvers.  Abstract DPLL(T).
 129  *
 130  * This is essentially an interface class.  The TheoryEngine has
 131  * pointers to Theory.  Note that only one specific Theory type (e.g.,
 132  * TheoryUF) can exist per NodeManager, because of how the
 133  * RegisteredAttr works.  (If you need multiple instances of the same
 134  * theory, you'll have to write a multiplexed theory that dispatches
 135  * all calls to them.)
 136  */
 137 class Theory {
 138
 139 private:
 140
 141   friend class ::CVC4::TheoryEngine;
 142
 143   // Disallow default construction, copy, assignment.
 144   Theory() CVC4_UNUSED;
 145   Theory(const Theory&) CVC4_UNUSED;
 146   Theory& operator=(const Theory&) CVC4_UNUSED;
 147
 148   /**
 149    * An integer identifying the type of the theory
 150    */
 151   TheoryId d_id;
 152
 153   /**
 154    * The SAT search context for the Theory.
 155    */
 156   context::Context* d_satContext;
 157
 158   /**
 159    * The user level assertion context for the Theory.
 160    */
 161   context::UserContext* d_userContext;
 162
 163   /**
 164    * Information about the logic we're operating within.
 165    */
 166   const LogicInfo& d_logicInfo;
 167
 168   /**
 169    * The assertFact() queue.
 170    *
 171    * These can not be TNodes as some atoms (such as equalities) are sent
 172    * across theories without being stored in a global map.
 173    */
 174   context::CDList<Assertion> d_facts;
 175
 176   /** Index into the head of the facts list */
 177   context::CDO<unsigned> d_factsHead;
 178
 179   /**
 180    * Add shared term to the theory.
 181    */
 182   void addSharedTermInternal(TNode node);
 183
 184   /**
 185    * Indices for splitting on the shared terms.
 186    */
 187   context::CDO<unsigned> d_sharedTermsIndex;
 188
 189   /**
 190    * The care graph the theory will use during combination.
 191    */
 192   CareGraph* d_careGraph;
 193
 194   /**
 195    * Reference to the quantifiers engine (or NULL, if quantifiers are
 196    * not supported or not enabled).
 197    */
 198   QuantifiersEngine* d_quantEngine;
 199
 200   // === STATISTICS ===
 201   /** time spent in theory combination */
 202   TimerStat d_computeCareGraphTime;
 203
 204   static std::string statName(TheoryId id, const char* statName) {
 205     std::stringstream ss;
 206     ss << "theory<" << id << ">::" << statName;
 207     return ss.str();
 208   }
 209
 210 protected:
 211
 212   /**
 213    * The only method to add suff to the care graph.
 214    */
 215   void addCarePair(TNode t1, TNode t2) {
 216     if (d_careGraph) {
 217       d_careGraph->insert(CarePair(t1, t2, d_id));
 218     }
 219   }
 220
 221   /**
 222    * The function should compute the care graph over the shared terms.
 223    * The default function returns all the pairs among the shared variables.
 224    */
 225   virtual void computeCareGraph();
 226
 227   /**
 228    * A list of shared terms that the theory has.
 229    */
 230   context::CDList<TNode> d_sharedTerms;
 231
 232   /**
 233    * Helper function for computeRelevantTerms
 234    */
 235   void collectTerms(TNode n, std::set<Node>& termSet) const;
 236   /**
 237    * Scans the current set of assertions and shared terms top-down
 238    * until a theory-leaf is reached, and adds all terms found to
 239    * termSet.  This is used by collectModelInfo to delimit the set of
 240    * terms that should be used when constructing a model
 241    */
 242   void computeRelevantTerms(std::set<Node>& termSet) const;
 243
 244   /**
 245    * Construct a Theory.
 246    */
 247   Theory(TheoryId id, context::Context* satContext, context::UserContext* userContext,
 248          OutputChannel& out, Valuation valuation, const LogicInfo& logicInfo) throw()
 249   : d_id(id)
 250   , d_satContext(satContext)
 251   , d_userContext(userContext)
 252   , d_logicInfo(logicInfo)
 253   , d_facts(satContext)
 254   , d_factsHead(satContext, 0)
 255   , d_sharedTermsIndex(satContext, 0)
 256   , d_careGraph(NULL)
 257   , d_quantEngine(NULL)
 258   , d_computeCareGraphTime(statName(id, "computeCareGraphTime"))
 259   , d_sharedTerms(satContext)
 260   , d_out(&out)
 261   , d_valuation(valuation)
 262   , d_proofEnabled(false)
 263   {
 264     StatisticsRegistry::registerStat(&d_computeCareGraphTime);
 265   }
 266
 267   /**
 268    * This is called at shutdown time by the TheoryEngine, just before
 269    * destruction.  It is important because there are destruction
 270    * ordering issues between PropEngine and Theory (based on what
 271    * hard-links to Nodes are outstanding).  As the fact queue might be
 272    * nonempty, we ensure here that it's clear.  If you overload this,
 273    * you must make an explicit call here to this->Theory::shutdown()
 274    * too.
 275    */
 276   virtual void shutdown() { }
 277
 278   /**
 279    * The output channel for the Theory.
 280    */
 281   OutputChannel* d_out;
 282
 283   /**
 284    * The valuation proxy for the Theory to communicate back with the
 285    * theory engine (and other theories).
 286    */
 287   Valuation d_valuation;
 288
 289   /**
 290    * Returns the next assertion in the assertFact() queue.
 291    *
 292    * @return the next assertion in the assertFact() queue
 293    */
 294   inline Assertion get();
 295
 296   const LogicInfo& getLogicInfo() const {
 297     return d_logicInfo;
 298   }
 299
 300   /**
 301    * The theory that owns the uninterpreted sort.
 302    */
 303   static TheoryId s_uninterpretedSortOwner;
 304
 305   void printFacts(std::ostream& os) const;
 306   void debugPrintFacts() const;
 307
 308   /**
 309    * Whether proofs are enabled
 310    *
 311    */
 312   bool d_proofEnabled;
 313
 314 public:
 315
 316   /**
 317    * Return the ID of the theory responsible for the given type.
 318    */
 319   static inline TheoryId theoryOf(TypeNode typeNode) {
 320     Trace("theory::internal") << "theoryOf(" << typeNode << ")" << std::endl;
 321     TheoryId id;
 322     while (typeNode.isPredicateSubtype()) {
 323       typeNode = typeNode.getSubtypeParentType();
 324     }
 325     if (typeNode.getKind() == kind::TYPE_CONSTANT) {
 326       id = typeConstantToTheoryId(typeNode.getConst<TypeConstant>());
 327     } else {
 328       id = kindToTheoryId(typeNode.getKind());
 329     }
 330     if (id == THEORY_BUILTIN) {
 331       Trace("theory::internal") << "theoryOf(" << typeNode << ") == " << s_uninterpretedSortOwner << std::endl;
 332       return s_uninterpretedSortOwner;
 333     }
 334     return id;
 335   }
 336
 337   /**
 338    * Returns the ID of the theory responsible for the given node.
 339    */
 340   static TheoryId theoryOf(TheoryOfMode mode, TNode node);
 341
 342   /**
 343    * Returns the ID of the theory responsible for the given node.
 344    */
 345   static inline TheoryId theoryOf(TNode node) {
 346     return theoryOf(options::theoryOfMode(), node);
 347   }
 348
 349   /**
 350    * Set the owner of the uninterpreted sort.
 351    */
 352   static void setUninterpretedSortOwner(TheoryId theory) {
 353     s_uninterpretedSortOwner = theory;
 354   }
 355
 356   /**
 357    * Get the owner of the uninterpreted sort.
 358    */
 359   static TheoryId getUninterpretedSortOwner() {
 360     return s_uninterpretedSortOwner;
 361   }
 362
 363   /**
 364    * Checks if the node is a leaf node of this theory
 365    */
 366   inline bool isLeaf(TNode node) const {
 367     return node.getNumChildren() == 0 || theoryOf(node) != d_id;
 368   }
 369
 370   /**
 371    * Checks if the node is a leaf node of a theory.
 372    */
 373   inline static bool isLeafOf(TNode node, TheoryId theoryId) {
 374     return node.getNumChildren() == 0 || theoryOf(node) != theoryId;
 375   }
 376
 377   /**
 378    * Returns true if the assertFact queue is empty
 379    */
 380   bool done() const throw() {
 381     return d_factsHead == d_facts.size();
 382   }
 383
 384   /**
 385    * Destructs a Theory.
 386    */
 387   virtual ~Theory();
 388
 389   /**
 390    * Subclasses of Theory may add additional efforts.  DO NOT CHECK
 391    * equality with one of these values (e.g. if STANDARD xxx) but
 392    * rather use range checks (or use the helper functions below).
 393    * Normally we call QUICK_CHECK or STANDARD; at the leaves we call
 394    * with FULL_EFFORT.
 395    */
 396   enum Effort {
 397     /**
 398      * Standard effort where theory need not do anything
 399      */
 400     EFFORT_STANDARD = 50,
 401     /**
 402      * Full effort requires the theory make sure its assertions are satisfiable or not
 403      */
 404     EFFORT_FULL = 100,
 405     /**
 406      * Combination effort means that the individual theories are already satisfied, and
 407      * it is time to put some effort into propagation of shared term equalities
 408      */
 409     EFFORT_COMBINATION = 150,
 410     /**
 411      * Last call effort, reserved for quantifiers.
 412      */
 413     EFFORT_LAST_CALL = 200
 414   };/* enum Effort */
 415
 416   static inline bool standardEffortOrMore(Effort e) CVC4_CONST_FUNCTION
 417     { return e >= EFFORT_STANDARD; }
 418   static inline bool standardEffortOnly(Effort e) CVC4_CONST_FUNCTION
 419     { return e >= EFFORT_STANDARD && e <  EFFORT_FULL; }
 420   static inline bool fullEffort(Effort e) CVC4_CONST_FUNCTION
 421     { return e == EFFORT_FULL; }
 422   static inline bool combination(Effort e) CVC4_CONST_FUNCTION
 423     { return e == EFFORT_COMBINATION; }
 424
 425   /**
 426    * Get the id for this Theory.
 427    */
 428   TheoryId getId() const {
 429     return d_id;
 430   }
 431
 432   /**
 433    * Get the SAT context associated to this Theory.
 434    */
 435   context::Context* getSatContext() const {
 436     return d_satContext;
 437   }
 438
 439   /**
 440    * Get the context associated to this Theory.
 441    */
 442   context::UserContext* getUserContext() const {
 443     return d_userContext;
 444   }
 445
 446   /**
 447    * Set the output channel associated to this theory.
 448    */
 449   void setOutputChannel(OutputChannel& out) {
 450     d_out = &out;
 451   }
 452
 453   /**
 454    * Get the output channel associated to this theory.
 455    */
 456   OutputChannel& getOutputChannel() {
 457     return *d_out;
 458   }
 459
 460   /**
 461    * Get the valuation associated to this theory.
 462    */
 463   Valuation& getValuation() {
 464     return d_valuation;
 465   }
 466
 467   /**
 468    * Get the quantifiers engine associated to this theory.
 469    */
 470   QuantifiersEngine* getQuantifiersEngine() {
 471     return d_quantEngine;
 472   }
 473
 474   /**
 475    * Get the quantifiers engine associated to this theory (const version).
 476    */
 477   const QuantifiersEngine* getQuantifiersEngine() const {
 478     return d_quantEngine;
 479   }
 480
 481   /**
 482    * Finish theory initialization.  At this point, options and the logic
 483    * setting are final, and the master equality engine and quantifiers
 484    * engine (if any) are initialized.  This base class implementation
 485    * does nothing.
 486    */
 487   virtual void finishInit() { }
 488
 489   /**
 490    * Some theories have kinds that are effectively definitions and
 491    * should be expanded before they are handled.  Definitions allow
 492    * a much wider range of actions than the normal forms given by the
 493    * rewriter; they can enable other theories and create new terms.
 494    * However no assumptions can be made about subterms having been
 495    * expanded or rewritten.  Where possible rewrite rules should be
 496    * used, definitions should only be used when rewrites are not
 497    * possible, for example in handling under-specified operations
 498    * using partially defined functions.
 499    */
 500   virtual Node expandDefinition(LogicRequest &logicRequest, Node node) {
 501     // by default, do nothing
 502     return node;
 503   }
 504
 505   /**
 506    * Pre-register a term.  Done one time for a Node per SAT context level.
 507    */
 508   virtual void preRegisterTerm(TNode) { }
 509
 510   /**
 511    * Assert a fact in the current context.
 512    */
 513   void assertFact(TNode assertion, bool isPreregistered) {
 514     Trace("theory") << "Theory<" << getId() << ">::assertFact[" << d_satContext->getLevel() << "](" << assertion << ", " << (isPreregistered ? "true" : "false") << ")" << std::endl;
 515     d_facts.push_back(Assertion(assertion, isPreregistered));
 516   }
 517
 518   /**
 519    * This method is called to notify a theory that the node n should
 520    * be considered a "shared term" by this theory
 521    */
 522   virtual void addSharedTerm(TNode n) { }
 523
 524   /**
 525    * Called to set the master equality engine.
 526    */
 527   virtual void setMasterEqualityEngine(eq::EqualityEngine* eq) { }
 528
 529   /**
 530    * Called to set the quantifiers engine.
 531    */
 532   virtual void setQuantifiersEngine(QuantifiersEngine* qe) {
 533     d_quantEngine = qe;
 534   }
 535
 536   /**
 537    * Return the current theory care graph. Theories should overload computeCareGraph to do
 538    * the actual computation, and use addCarePair to add pairs to the care graph.
 539    */
 540   void getCareGraph(CareGraph& careGraph) {
 541     Trace("sharing") << "Theory<" << getId() << ">::getCareGraph()" << std::endl;
 542     TimerStat::CodeTimer computeCareGraphTime(d_computeCareGraphTime);
 543     d_careGraph = &careGraph;
 544     computeCareGraph();
 545     d_careGraph = NULL;
 546   }
 547
 548   /**
 549    * Return the status of two terms in the current context. Should be implemented in
 550    * sub-theories to enable more efficient theory-combination.
 551    */
 552   virtual EqualityStatus getEqualityStatus(TNode a, TNode b) { return EQUALITY_UNKNOWN; }
 553
 554   /**
 555    * Return the model value of the give shared term (or null if not available).
 556    */
 557   virtual Node getModelValue(TNode var) { return Node::null(); }
 558
 559   /**
 560    * Check the current assignment's consistency.
 561    *
 562    * An implementation of check() is required to either:
 563    * - return a conflict on the output channel,
 564    * - be interrupted,
 565    * - throw an exception
 566    * - or call get() until done() is true.
 567    */
 568   virtual void check(Effort level = EFFORT_FULL) { }
 569
 570   /**
 571    * T-propagate new literal assignments in the current context.
 572    */
 573   virtual void propagate(Effort level = EFFORT_FULL) { }
 574
 575   /**
 576    * Return an explanation for the literal represented by parameter n
 577    * (which was previously propagated by this theory).
 578    */
 579   virtual Node explain(TNode n) {
 580     Unimplemented("Theory %s propagated a node but doesn't implement the "
 581                   "Theory::explain() interface!", identify().c_str());
 582   }
 583
 584   /**
 585    * Get all relevant information in this theory regarding the current
 586    * model.  This should be called after a call to check( FULL_EFFORT )
 587    * for all theories with no conflicts and no lemmas added.
 588    * If fullModel is true, then we must specify sufficient information for
 589    * the model class to construct constant representatives for each equivalence
 590    * class.
 591    */
 592   virtual void collectModelInfo( TheoryModel* m, bool fullModel ){ }
 593
 594   /**
 595    * Return a decision request, if the theory has one, or the NULL node
 596    * otherwise.
 597    */
 598   virtual Node getNextDecisionRequest() { return Node(); }
 599
 600   /**
 601    * Statically learn from assertion "in," which has been asserted
 602    * true at the top level.  The theory should only add (via
 603    * ::operator<< or ::append()) to the "learned" builder---it should
 604    * *never* clear it.  It is a conjunction to add to the formula at
 605    * the top-level and may contain other theories' contributions.
 606    */
 607   virtual void ppStaticLearn(TNode in, NodeBuilder<>& learned) { }
 608
 609   enum PPAssertStatus {
 610     /** Atom has been solved  */
 611     PP_ASSERT_STATUS_SOLVED,
 612     /** Atom has not been solved */
 613     PP_ASSERT_STATUS_UNSOLVED,
 614     /** Atom is inconsistent */
 615     PP_ASSERT_STATUS_CONFLICT
 616   };
 617
 618   /**
 619    * Given a literal, add the solved substitutions to the map, if any.
 620    * The method should return true if the literal can be safely removed.
 621    */
 622   virtual PPAssertStatus ppAssert(TNode in, SubstitutionMap& outSubstitutions);
 623
 624   /**
 625    * Given an atom of the theory coming from the input formula, this
 626    * method can be overridden in a theory implementation to rewrite
 627    * the atom into an equivalent form.  This is only called just
 628    * before an input atom to the engine.
 629    */
 630   virtual Node ppRewrite(TNode atom) { return atom; }
 631
 632   /**
 633    * Don't preprocess subterm of this term
 634    */
 635   virtual bool ppDontRewriteSubterm(TNode atom) { return false; }
 636
 637   /**
 638    * A Theory is called with presolve exactly one time per user
 639    * check-sat.  presolve() is called after preregistration,
 640    * rewriting, and Boolean propagation, (other theories'
 641    * propagation?), but the notified Theory has not yet had its
 642    * check() or propagate() method called.  A Theory may empty its
 643    * assertFact() queue using get().  A Theory can raise conflicts,
 644    * add lemmas, and propagate literals during presolve().
 645    *
 646    * NOTE: The presolve property must be added to the kinds file for
 647    * the theory.
 648    */
 649   virtual void presolve() { }
 650
 651   /**
 652    * A Theory is called with postsolve exactly one time per user
 653    * check-sat.  postsolve() is called after the query has completed
 654    * (regardless of whether sat, unsat, or unknown), and after any
 655    * model-querying related to the query has been performed.
 656    * After this call, the theory will not get another check() or
 657    * propagate() call until presolve() is called again.  A Theory
 658    * cannot raise conflicts, add lemmas, or propagate literals during
 659    * postsolve().
 660    */
 661   virtual void postsolve() { }
 662
 663   /**
 664    * Notification sent to the theory wheneven the search restarts.
 665    * Serves as a good time to do some clean-up work, and you can
 666    * assume you're at DL 0 for the purposes of Contexts.  This function
 667    * should not use the output channel.
 668    */
 669   virtual void notifyRestart() { }
 670
 671   /**
 672    * Identify this theory (for debugging, dynamic configuration,
 673    * etc..)
 674    */
 675   virtual std::string identify() const = 0;
 676
 677   /** Set user attribute
 678     * This function is called when an attribute is set by a user.  In SMT-LIBv2 this is done
 679     *  via the syntax (! n :attr)
 680     */
 681   virtual void setUserAttribute(const std::string& attr, Node n, std::vector<Node> node_values, std::string str_value) {
 682     Unimplemented("Theory %s doesn't support Theory::setUserAttribute interface",
 683                   identify().c_str());
 684   }
 685
 686   /** A set of theories */
 687   typedef uint32_t Set;
 688
 689   /** A set of all theories */
 690   static const Set AllTheories = (1 << theory::THEORY_LAST) - 1;
 691
 692   /** Pops a first theory off the set */
 693   static inline TheoryId setPop(Set& set) {
 694     uint32_t i = ffs(set); // Find First Set (bit)
 695     if (i == 0) { return THEORY_LAST; }
 696     TheoryId id = (TheoryId)(i-1);
 697     set = setRemove(id, set);
 698     return id;
 699   }
 700
 701   /** Returns the size of a set of theories */
 702   static inline size_t setSize(Set set) {
 703     size_t count = 0;
 704     while (setPop(set) != THEORY_LAST) {
 705       ++ count;
 706     }
 707     return count;
 708   }
 709
 710   /** Returns the index size of a set of theories */
 711   static inline size_t setIndex(TheoryId id, Set set) {
 712     Assert (setContains(id, set));
 713     size_t count = 0;
 714     while (setPop(set) != id) {
 715       ++ count;
 716     }
 717     return count;
 718   }
 719
 720   /** Add the theory to the set. If no set specified, just returns a singleton set */
 721   static inline Set setInsert(TheoryId theory, Set set = 0) {
 722     return set | (1 << theory);
 723   }
 724
 725   /** Add the theory to the set. If no set specified, just returns a singleton set */
 726   static inline Set setRemove(TheoryId theory, Set set = 0) {
 727     return setDifference(set, setInsert(theory));
 728   }
 729
 730   /** Check if the set contains the theory */
 731   static inline bool setContains(TheoryId theory, Set set) {
 732     return set & (1 << theory);
 733   }
 734
 735   static inline Set setComplement(Set a) {
 736     return (~a) & AllTheories;
 737   }
 738
 739   static inline Set setIntersection(Set a, Set b) {
 740     return a & b;
 741   }
 742
 743   static inline Set setUnion(Set a, Set b) {
 744     return a | b;
 745   }
 746
 747   /** a - b  */
 748   static inline Set setDifference(Set a, Set b) {
 749     return (~b) & a;
 750   }
 751
 752   static inline std::string setToString(theory::Theory::Set theorySet) {
 753     std::stringstream ss;
 754     ss << "[";
 755     for(unsigned theoryId = 0; theoryId < theory::THEORY_LAST; ++theoryId) {
 756       if (theory::Theory::setContains((theory::TheoryId)theoryId, theorySet)) {
 757         ss << (theory::TheoryId) theoryId << " ";
 758       }
 759     }
 760     ss << "]";
 761     return ss.str();
 762   }
 763
 764   typedef context::CDList<Assertion>::const_iterator assertions_iterator;
 765
 766   /**
 767    * Provides access to the facts queue, primarily intended for theory
 768    * debugging purposes.
 769    *
 770    * @return the iterator to the beginning of the fact queue
 771    */
 772   assertions_iterator facts_begin() const {
 773     return d_facts.begin();
 774   }
 775
 776   /**
 777    * Provides access to the facts queue, primarily intended for theory
 778    * debugging purposes.
 779    *
 780    * @return the iterator to the end of the fact queue
 781    */
 782   assertions_iterator facts_end() const {
 783     return d_facts.end();
 784   }
 785
 786   typedef context::CDList<TNode>::const_iterator shared_terms_iterator;
 787
 788   /**
 789    * Provides access to the shared terms, primarily intended for theory
 790    * debugging purposes.
 791    *
 792    * @return the iterator to the beginning of the shared terms list
 793    */
 794   shared_terms_iterator shared_terms_begin() const {
 795     return d_sharedTerms.begin();
 796   }
 797
 798   /**
 799    * Provides access to the facts queue, primarily intended for theory
 800    * debugging purposes.
 801    *
 802    * @return the iterator to the end of the shared terms list
 803    */
 804   shared_terms_iterator shared_terms_end() const {
 805     return d_sharedTerms.end();
 806   }
 807
 808
 809   /**
 810    * This is a utility function for constructing a copy of the currently shared terms
 811    * in a queriable form.  As this is
 812    */
 813   std::hash_set<TNode, TNodeHashFunction> currentlySharedTerms() const;
 814
 815   /**
 816    * This allows the theory to be queried for whether a literal, lit, is
 817    * entailed by the theory.  This returns a pair of a Boolean and a node E.
 818    *
 819    * If the Boolean is true, then E is a formula that entails lit and E is propositionally
 820    * entailed by the assertions to the theory.
 821    *
 822    * If the Boolean is false, it is "unknown" if lit is entailed and E may be
 823    * any node.
 824    *
 825    * The literal lit is either an atom a or (not a), which must belong to the theory:
 826    *   There is some TheoryOfMode m s.t. Theory::theoryOf(m, a) == this->getId().
 827    *
 828    * There are NO assumptions that a or the subterms of a have been
 829    * preprocessed in any form.  This includes ppRewrite, rewriting,
 830    * preregistering, registering, definition expansion or ITE removal!
 831    *
 832    * Theories are free to limit the amount of effort they use and so may
 833    * always opt to return "unknown".  Both "unknown" and "not entailed",
 834    * may return for E a non-boolean Node (e.g. Node::null()).  (There is no explicit output
 835    * for the negation of lit is entailed.)
 836    *
 837    * If lit is theory valid, the return result may be the Boolean constant
 838    * true for E.
 839    *
 840    * If lit is entailed by multiple assertions on the theory's getFact()
 841    * queue, a_1, a_2, ... and a_k, this may return E=(and a_1 a_2 ... a_k) or
 842    * another theory entailed explanation E=(and (and a_1 a_2) (and a3 a_4) ... a_k)
 843    *
 844    * If lit is entailed by a single assertion on the theory's getFact()
 845    * queue, say a, this may return E=a.
 846    *
 847    * The theory may always return false!
 848    *
 849    * The search is controlled by the parameter params.  For default behavior,
 850    * this may be left NULL.
 851    *
 852    * Theories that want parameters extend the virtual EntailmentCheckParameters
 853    * class.  Users ask the theory for an appropriate subclass from the theory
 854    * and configure that.  How this is implemented is on a per theory basis.
 855    *
 856    * The search may provide additional output to guide the user of
 857    * this function.  This output is stored in a EntailmentCheckSideEffects*
 858    * output parameter.  The implementation of this is theory specific.  For
 859    * no output, this is NULL.
 860    *
 861    * Theories may not touch their output stream during an entailment check.
 862    *
 863    * @param  lit     a literal belonging to the theory.
 864    * @param  params  the control parameters for the entailment check.
 865    * @param  out     a theory specific output object of the entailment search.
 866    * @return         a pair <b,E> s.t. if b is true, then a formula E such that
 867    * E |= lit in the theory.
 868    */
 869   virtual std::pair<bool, Node> entailmentCheck(TNode lit, const EntailmentCheckParameters* params = NULL, EntailmentCheckSideEffects* out = NULL);
 870
 871 };/* class Theory */
 872
 873 std::ostream& operator<<(std::ostream& os, theory::Theory::Effort level);
 874 inline std::ostream& operator<<(std::ostream& out, const theory::Assertion& a);
 875
 876 inline theory::Assertion Theory::get() {
 877   Assert( !done(), "Theory::get() called with assertion queue empty!" );
 878
 879   // Get the assertion
 880   Assertion fact = d_facts[d_factsHead];
 881   d_factsHead = d_factsHead + 1;
 882
 883   Trace("theory") << "Theory::get() => " << fact << " (" << d_facts.size() - d_factsHead << " left)" << std::endl;
 884
 885   if(Dump.isOn("state")) {
 886     Dump("state") << AssertCommand(fact.assertion.toExpr());
 887   }
 888
 889   return fact;
 890 }
 891
 892 inline std::ostream& operator<<(std::ostream& out, const theory::Assertion& a) {
 893   return out << a.assertion;
 894 }
 895
 896 inline std::ostream& operator<<(std::ostream& out,
 897                                 const CVC4::theory::Theory& theory) {
 898   return out << theory.identify();
 899 }
 900
 901 inline std::ostream& operator << (std::ostream& out, theory::Theory::PPAssertStatus status) {
 902   switch (status) {
 903   case theory::Theory::PP_ASSERT_STATUS_SOLVED:
 904     out << "SOLVE_STATUS_SOLVED"; break;
 905   case theory::Theory::PP_ASSERT_STATUS_UNSOLVED:
 906     out << "SOLVE_STATUS_UNSOLVED"; break;
 907   case theory::Theory::PP_ASSERT_STATUS_CONFLICT:
 908     out << "SOLVE_STATUS_CONFLICT"; break;
 909   default:
 910     Unhandled();
 911   }
 912   return out;
 913 }
 914
 915 class EntailmentCheckParameters {
 916 private:
 917   TheoryId d_tid;
 918 protected:
 919   EntailmentCheckParameters(TheoryId tid);
 920 public:
 921   TheoryId getTheoryId() const;
 922   virtual ~EntailmentCheckParameters();
 923 };/* class EntailmentCheckParameters */
 924
 925 class EntailmentCheckSideEffects {
 926 private:
 927   TheoryId d_tid;
 928 protected:
 929   EntailmentCheckSideEffects(TheoryId tid);
 930 public:
 931   TheoryId getTheoryId() const;
 932   virtual ~EntailmentCheckSideEffects();
 933 };/* class EntailmentCheckSideEffects */
 934
 935 }/* CVC4::theory namespace */
 936 }/* CVC4 namespace */
 937
 938 #endif /* __CVC4__THEORY__THEORY_H */