src/theory/theory.h

   1 /*********************                                                        */
   2 /*! \file theory.h
   3  ** \verbatim
   4  ** Top contributors (to current version):
   5  **   Morgan Deters, Dejan Jovanovic, Tim King
   6  ** This file is part of the CVC4 project.
   7  ** Copyright (c) 2009-2019 by the authors listed in the file AUTHORS
   8  ** in the top-level source directory) and their institutional affiliations.
   9  ** All rights reserved.  See the file COPYING in the top-level source
  10  ** directory for licensing 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 <iosfwd>
  23 #include <map>
  24 #include <set>
  25 #include <string>
  26 #include <unordered_set>
  27
  28 #include "context/cdhashset.h"
  29 #include "context/cdlist.h"
  30 #include "context/cdo.h"
  31 #include "context/context.h"
  32 #include "expr/node.h"
  33 #include "lib/ffs.h"
  34 #include "options/options.h"
  35 #include "options/theory_options.h"
  36 #include "smt/command.h"
  37 #include "smt/dump.h"
  38 #include "smt/logic_request.h"
  39 #include "theory/assertion.h"
  40 #include "theory/care_graph.h"
  41 #include "theory/decision_manager.h"
  42 #include "theory/logic_info.h"
  43 #include "theory/output_channel.h"
  44 #include "theory/theory_id.h"
  45 #include "theory/theory_rewriter.h"
  46 #include "theory/valuation.h"
  47 #include "util/statistics_registry.h"
  48
  49 namespace CVC4 {
  50
  51 class TheoryEngine;
  52
  53 namespace theory {
  54
  55 class QuantifiersEngine;
  56 class TheoryModel;
  57 class SubstitutionMap;
  58 class ExtTheory;
  59
  60 class EntailmentCheckParameters;
  61 class EntailmentCheckSideEffects;
  62
  63 namespace rrinst {
  64   class CandidateGenerator;
  65 }/* CVC4::theory::rrinst namespace */
  66
  67 namespace eq {
  68   class EqualityEngine;
  69 }/* CVC4::theory::eq namespace */
  70
  71 /**
  72  * Base class for T-solvers.  Abstract DPLL(T).
  73  *
  74  * This is essentially an interface class.  The TheoryEngine has
  75  * pointers to Theory.  Note that only one specific Theory type (e.g.,
  76  * TheoryUF) can exist per NodeManager, because of how the
  77  * RegisteredAttr works.  (If you need multiple instances of the same
  78  * theory, you'll have to write a multiplexed theory that dispatches
  79  * all calls to them.)
  80  */
  81 class Theory {
  82
  83 private:
  84
  85   friend class ::CVC4::TheoryEngine;
  86
  87   // Disallow default construction, copy, assignment.
  88   Theory() = delete;
  89   Theory(const Theory&) = delete;
  90   Theory& operator=(const Theory&) = delete;
  91
  92   /** An integer identifying the type of the theory. */
  93   TheoryId d_id;
  94
  95   /** Name of this theory instance. Along with the TheoryId this should provide
  96    * an unique string identifier for each instance of a Theory class. We need
  97    * this to ensure unique statistics names over multiple theory instances. */
  98   std::string d_instanceName;
  99
 100   /** The SAT search context for the Theory. */
 101   context::Context* d_satContext;
 102
 103   /** The user level assertion context for the Theory. */
 104   context::UserContext* d_userContext;
 105
 106   /** Information about the logic we're operating within. */
 107   const LogicInfo& d_logicInfo;
 108
 109   /**
 110    * The assertFact() queue.
 111    *
 112    * These can not be TNodes as some atoms (such as equalities) are sent
 113    * across theories without being stored in a global map.
 114    */
 115   context::CDList<Assertion> d_facts;
 116
 117   /** Index into the head of the facts list */
 118   context::CDO<unsigned> d_factsHead;
 119
 120   /** Add shared term to the theory. */
 121   void addSharedTermInternal(TNode node);
 122
 123   /** Indices for splitting on the shared terms. */
 124   context::CDO<unsigned> d_sharedTermsIndex;
 125
 126   /** The care graph the theory will use during combination. */
 127   CareGraph* d_careGraph;
 128
 129   /**
 130    * Pointer to the quantifiers engine (or NULL, if quantifiers are not
 131    * supported or not enabled). Not owned by the theory.
 132    */
 133   QuantifiersEngine* d_quantEngine;
 134
 135   /** Pointer to the decision manager. */
 136   DecisionManager* d_decManager;
 137
 138   /** Extended theory module or NULL. Owned by the theory. */
 139   ExtTheory* d_extTheory;
 140
 141  protected:
 142
 143
 144   // === STATISTICS ===
 145   /** time spent in check calls */
 146   TimerStat d_checkTime;
 147   /** time spent in theory combination */
 148   TimerStat d_computeCareGraphTime;
 149
 150   /**
 151    * The only method to add suff to the care graph.
 152    */
 153   void addCarePair(TNode t1, TNode t2);
 154
 155   /**
 156    * The function should compute the care graph over the shared terms.
 157    * The default function returns all the pairs among the shared variables.
 158    */
 159   virtual void computeCareGraph();
 160
 161   /**
 162    * A list of shared terms that the theory has.
 163    */
 164   context::CDList<TNode> d_sharedTerms;
 165
 166   /**
 167    * Helper function for computeRelevantTerms
 168    */
 169   void collectTerms(TNode n,
 170                     std::set<Kind>& irrKinds,
 171                     std::set<Node>& termSet) const;
 172
 173   /**
 174    * Scans the current set of assertions and shared terms top-down
 175    * until a theory-leaf is reached, and adds all terms found to
 176    * termSet.  This is used by collectModelInfo to delimit the set of
 177    * terms that should be used when constructing a model.
 178    *
 179    * irrKinds: The kinds of terms that appear in assertions that should *not*
 180    * be included in termSet. Note that the kinds EQUAL and NOT are always
 181    * treated as irrelevant kinds.
 182    *
 183    * includeShared: Whether to include shared terms in termSet. Notice that
 184    * shared terms are not influenced by irrKinds.
 185    */
 186   void computeRelevantTerms(std::set<Node>& termSet,
 187                             std::set<Kind>& irrKinds,
 188                             bool includeShared = true) const;
 189   /** same as above, but with empty irrKinds */
 190   void computeRelevantTerms(std::set<Node>& termSet, bool includeShared = true) const;
 191
 192   /**
 193    * Construct a Theory.
 194    *
 195    * The pair <id, instance> is assumed to uniquely identify this Theory
 196    * w.r.t. the SmtEngine.
 197    */
 198   Theory(TheoryId id,
 199          context::Context* satContext,
 200          context::UserContext* userContext,
 201          OutputChannel& out,
 202          Valuation valuation,
 203          const LogicInfo& logicInfo,
 204          std::string instance = "");  // taking : No default.
 205
 206   /**
 207    * This is called at shutdown time by the TheoryEngine, just before
 208    * destruction.  It is important because there are destruction
 209    * ordering issues between PropEngine and Theory (based on what
 210    * hard-links to Nodes are outstanding).  As the fact queue might be
 211    * nonempty, we ensure here that it's clear.  If you overload this,
 212    * you must make an explicit call here to this->Theory::shutdown()
 213    * too.
 214    */
 215   virtual void shutdown() { }
 216
 217   /**
 218    * The output channel for the Theory.
 219    */
 220   OutputChannel* d_out;
 221
 222   /**
 223    * The valuation proxy for the Theory to communicate back with the
 224    * theory engine (and other theories).
 225    */
 226   Valuation d_valuation;
 227
 228   /**
 229    * Whether proofs are enabled
 230    *
 231    */
 232   bool d_proofsEnabled;
 233
 234   /**
 235    * Returns the next assertion in the assertFact() queue.
 236    *
 237    * @return the next assertion in the assertFact() queue
 238    */
 239   inline Assertion get();
 240
 241   const LogicInfo& getLogicInfo() const {
 242     return d_logicInfo;
 243   }
 244
 245   /**
 246    * The theory that owns the uninterpreted sort.
 247    */
 248   static TheoryId s_uninterpretedSortOwner;
 249
 250   void printFacts(std::ostream& os) const;
 251   void debugPrintFacts() const;
 252
 253 public:
 254
 255   /**
 256    * Return the ID of the theory responsible for the given type.
 257    */
 258   static inline TheoryId theoryOf(TypeNode typeNode) {
 259     Trace("theory::internal") << "theoryOf(" << typeNode << ")" << std::endl;
 260     TheoryId id;
 261     if (typeNode.getKind() == kind::TYPE_CONSTANT) {
 262       id = typeConstantToTheoryId(typeNode.getConst<TypeConstant>());
 263     } else {
 264       id = kindToTheoryId(typeNode.getKind());
 265     }
 266     if (id == THEORY_BUILTIN) {
 267       Trace("theory::internal") << "theoryOf(" << typeNode << ") == " << s_uninterpretedSortOwner << std::endl;
 268       return s_uninterpretedSortOwner;
 269     }
 270     return id;
 271   }
 272
 273   /**
 274    * Returns the ID of the theory responsible for the given node.
 275    */
 276   static TheoryId theoryOf(options::TheoryOfMode mode, TNode node);
 277
 278   /**
 279    * Returns the ID of the theory responsible for the given node.
 280    */
 281   static inline TheoryId theoryOf(TNode node) {
 282     return theoryOf(options::theoryOfMode(), node);
 283   }
 284
 285   /**
 286    * Set the owner of the uninterpreted sort.
 287    */
 288   static void setUninterpretedSortOwner(TheoryId theory) {
 289     s_uninterpretedSortOwner = theory;
 290   }
 291
 292   /**
 293    * Get the owner of the uninterpreted sort.
 294    */
 295   static TheoryId getUninterpretedSortOwner() {
 296     return s_uninterpretedSortOwner;
 297   }
 298
 299   /**
 300    * Checks if the node is a leaf node of this theory
 301    */
 302   inline bool isLeaf(TNode node) const {
 303     return node.getNumChildren() == 0 || theoryOf(node) != d_id;
 304   }
 305
 306   /**
 307    * Checks if the node is a leaf node of a theory.
 308    */
 309   inline static bool isLeafOf(TNode node, TheoryId theoryId) {
 310     return node.getNumChildren() == 0 || theoryOf(node) != theoryId;
 311   }
 312
 313   /** Returns true if the assertFact queue is empty*/
 314   bool done() const { return d_factsHead == d_facts.size(); }
 315   /**
 316    * Destructs a Theory.
 317    */
 318   virtual ~Theory();
 319
 320   /**
 321    * Creates a new theory rewriter for the theory.
 322    */
 323   virtual std::unique_ptr<TheoryRewriter> mkTheoryRewriter() = 0;
 324
 325   /**
 326    * Subclasses of Theory may add additional efforts.  DO NOT CHECK
 327    * equality with one of these values (e.g. if STANDARD xxx) but
 328    * rather use range checks (or use the helper functions below).
 329    * Normally we call QUICK_CHECK or STANDARD; at the leaves we call
 330    * with FULL_EFFORT.
 331    */
 332   enum Effort {
 333     /**
 334      * Standard effort where theory need not do anything
 335      */
 336     EFFORT_STANDARD = 50,
 337     /**
 338      * Full effort requires the theory make sure its assertions are satisfiable or not
 339      */
 340     EFFORT_FULL = 100,
 341     /**
 342      * Combination effort means that the individual theories are already satisfied, and
 343      * it is time to put some effort into propagation of shared term equalities
 344      */
 345     EFFORT_COMBINATION = 150,
 346     /**
 347      * Last call effort, reserved for quantifiers.
 348      */
 349     EFFORT_LAST_CALL = 200
 350   };/* enum Effort */
 351
 352   static inline bool standardEffortOrMore(Effort e) CVC4_CONST_FUNCTION
 353     { return e >= EFFORT_STANDARD; }
 354   static inline bool standardEffortOnly(Effort e) CVC4_CONST_FUNCTION
 355     { return e >= EFFORT_STANDARD && e <  EFFORT_FULL; }
 356   static inline bool fullEffort(Effort e) CVC4_CONST_FUNCTION
 357     { return e == EFFORT_FULL; }
 358   static inline bool combination(Effort e) CVC4_CONST_FUNCTION
 359     { return e == EFFORT_COMBINATION; }
 360
 361   /**
 362    * Get the id for this Theory.
 363    */
 364   TheoryId getId() const {
 365     return d_id;
 366   }
 367
 368   /**
 369    * Get the SAT context associated to this Theory.
 370    */
 371   context::Context* getSatContext() const {
 372     return d_satContext;
 373   }
 374
 375   /**
 376    * Get the context associated to this Theory.
 377    */
 378   context::UserContext* getUserContext() const {
 379     return d_userContext;
 380   }
 381
 382   /**
 383    * Set the output channel associated to this theory.
 384    */
 385   void setOutputChannel(OutputChannel& out) {
 386     d_out = &out;
 387   }
 388
 389   /**
 390    * Get the output channel associated to this theory.
 391    */
 392   OutputChannel& getOutputChannel() {
 393     return *d_out;
 394   }
 395
 396   /**
 397    * Get the valuation associated to this theory.
 398    */
 399   Valuation& getValuation() {
 400     return d_valuation;
 401   }
 402
 403   /**
 404    * Get the quantifiers engine associated to this theory.
 405    */
 406   QuantifiersEngine* getQuantifiersEngine() {
 407     return d_quantEngine;
 408   }
 409
 410   /**
 411    * Get the quantifiers engine associated to this theory (const version).
 412    */
 413   const QuantifiersEngine* getQuantifiersEngine() const {
 414     return d_quantEngine;
 415   }
 416
 417   /** Get the decision manager associated to this theory. */
 418   DecisionManager* getDecisionManager() { return d_decManager; }
 419
 420   /**
 421    * Finish theory initialization.  At this point, options and the logic
 422    * setting are final, and the master equality engine and quantifiers
 423    * engine (if any) are initialized.  This base class implementation
 424    * does nothing.
 425    */
 426   virtual void finishInit() { }
 427
 428   /**
 429    * Some theories have kinds that are effectively definitions and
 430    * should be expanded before they are handled.  Definitions allow
 431    * a much wider range of actions than the normal forms given by the
 432    * rewriter; they can enable other theories and create new terms.
 433    * However no assumptions can be made about subterms having been
 434    * expanded or rewritten.  Where possible rewrite rules should be
 435    * used, definitions should only be used when rewrites are not
 436    * possible, for example in handling under-specified operations
 437    * using partially defined functions.
 438    *
 439    * Some theories like sets use expandDefinition as a "context
 440    * independent preRegisterTerm".  This is required for cases where
 441    * a theory wants to be notified about a term before preprocessing
 442    * and simplification but doesn't necessarily want to rewrite it.
 443    */
 444   virtual Node expandDefinition(LogicRequest &logicRequest, Node node) {
 445     // by default, do nothing
 446     return node;
 447   }
 448
 449   /**
 450    * Pre-register a term.  Done one time for a Node per SAT context level.
 451    */
 452   virtual void preRegisterTerm(TNode) { }
 453
 454   /**
 455    * Assert a fact in the current context.
 456    */
 457   void assertFact(TNode assertion, bool isPreregistered) {
 458     Trace("theory") << "Theory<" << getId() << ">::assertFact["
 459                     << d_satContext->getLevel() << "](" << assertion << ", "
 460                     << (isPreregistered ? "true" : "false") << ")" << std::endl;
 461     d_facts.push_back(Assertion(assertion, isPreregistered));
 462   }
 463
 464   /**
 465    * This method is called to notify a theory that the node n should
 466    * be considered a "shared term" by this theory
 467    */
 468   virtual void addSharedTerm(TNode n) { }
 469
 470   /**
 471    * Called to set the master equality engine.
 472    */
 473   virtual void setMasterEqualityEngine(eq::EqualityEngine* eq) { }
 474
 475   /** Called to set the quantifiers engine. */
 476   void setQuantifiersEngine(QuantifiersEngine* qe);
 477   /** Called to set the decision manager. */
 478   void setDecisionManager(DecisionManager* dm);
 479
 480   /** Setup an ExtTheory module for this Theory. Can only be called once. */
 481   void setupExtTheory();
 482
 483   /**
 484    * Return the current theory care graph. Theories should overload
 485    * computeCareGraph to do the actual computation, and use addCarePair to add
 486    * pairs to the care graph.
 487    */
 488   void getCareGraph(CareGraph* careGraph);
 489
 490   /**
 491    * Return the status of two terms in the current context. Should be
 492    * implemented in sub-theories to enable more efficient theory-combination.
 493    */
 494   virtual EqualityStatus getEqualityStatus(TNode a, TNode b) {
 495     return EQUALITY_UNKNOWN;
 496   }
 497
 498   /**
 499    * Return the model value of the give shared term (or null if not available).
 500    */
 501   virtual Node getModelValue(TNode var) { return Node::null(); }
 502
 503   /**
 504    * Check the current assignment's consistency.
 505    *
 506    * An implementation of check() is required to either:
 507    * - return a conflict on the output channel,
 508    * - be interrupted,
 509    * - throw an exception
 510    * - or call get() until done() is true.
 511    */
 512   virtual void check(Effort level = EFFORT_FULL) { }
 513
 514   /** Needs last effort check? */
 515   virtual bool needsCheckLastEffort() { return false; }
 516
 517   /** T-propagate new literal assignments in the current context. */
 518   virtual void propagate(Effort level = EFFORT_FULL) { }
 519
 520   /**
 521    * Return an explanation for the literal represented by parameter n
 522    * (which was previously propagated by this theory).
 523    */
 524   virtual Node explain(TNode n) {
 525     Unimplemented() << "Theory " << identify()
 526                     << " propagated a node but doesn't implement the "
 527                        "Theory::explain() interface!";
 528   }
 529
 530   /**
 531    * Get all relevant information in this theory regarding the current
 532    * model.  This should be called after a call to check( FULL_EFFORT )
 533    * for all theories with no conflicts and no lemmas added.
 534    *
 535    * This method returns true if and only if the equality engine of m is
 536    * consistent as a result of this call.
 537    */
 538   virtual bool collectModelInfo(TheoryModel* m) { return true; }
 539   /** if theories want to do something with model after building, do it here */
 540   virtual void postProcessModel( TheoryModel* m ){ }
 541   /**
 542    * Statically learn from assertion "in," which has been asserted
 543    * true at the top level.  The theory should only add (via
 544    * ::operator<< or ::append()) to the "learned" builder---it should
 545    * *never* clear it.  It is a conjunction to add to the formula at
 546    * the top-level and may contain other theories' contributions.
 547    */
 548   virtual void ppStaticLearn(TNode in, NodeBuilder<>& learned) { }
 549
 550   enum PPAssertStatus {
 551     /** Atom has been solved  */
 552     PP_ASSERT_STATUS_SOLVED,
 553     /** Atom has not been solved */
 554     PP_ASSERT_STATUS_UNSOLVED,
 555     /** Atom is inconsistent */
 556     PP_ASSERT_STATUS_CONFLICT
 557   };
 558
 559   /**
 560    * Given a literal, add the solved substitutions to the map, if any.
 561    * The method should return true if the literal can be safely removed.
 562    */
 563   virtual PPAssertStatus ppAssert(TNode in, SubstitutionMap& outSubstitutions);
 564
 565   /**
 566    * Given an atom of the theory coming from the input formula, this
 567    * method can be overridden in a theory implementation to rewrite
 568    * the atom into an equivalent form.  This is only called just
 569    * before an input atom to the engine.
 570    */
 571   virtual Node ppRewrite(TNode atom) { return atom; }
 572
 573   /**
 574    * Notify preprocessed assertions. Called on new assertions after
 575    * preprocessing before they are asserted to theory engine.
 576    */
 577   virtual void ppNotifyAssertions(const std::vector<Node>& assertions) {}
 578
 579   /**
 580    * A Theory is called with presolve exactly one time per user
 581    * check-sat.  presolve() is called after preregistration,
 582    * rewriting, and Boolean propagation, (other theories'
 583    * propagation?), but the notified Theory has not yet had its
 584    * check() or propagate() method called.  A Theory may empty its
 585    * assertFact() queue using get().  A Theory can raise conflicts,
 586    * add lemmas, and propagate literals during presolve().
 587    *
 588    * NOTE: The presolve property must be added to the kinds file for
 589    * the theory.
 590    */
 591   virtual void presolve() { }
 592
 593   /**
 594    * A Theory is called with postsolve exactly one time per user
 595    * check-sat.  postsolve() is called after the query has completed
 596    * (regardless of whether sat, unsat, or unknown), and after any
 597    * model-querying related to the query has been performed.
 598    * After this call, the theory will not get another check() or
 599    * propagate() call until presolve() is called again.  A Theory
 600    * cannot raise conflicts, add lemmas, or propagate literals during
 601    * postsolve().
 602    */
 603   virtual void postsolve() { }
 604
 605   /**
 606    * Notification sent to the theory wheneven the search restarts.
 607    * Serves as a good time to do some clean-up work, and you can
 608    * assume you're at DL 0 for the purposes of Contexts.  This function
 609    * should not use the output channel.
 610    */
 611   virtual void notifyRestart() { }
 612
 613   /**
 614    * Identify this theory (for debugging, dynamic configuration,
 615    * etc..)
 616    */
 617   virtual std::string identify() const = 0;
 618
 619   /** Set user attribute
 620     * This function is called when an attribute is set by a user.  In SMT-LIBv2 this is done
 621     *  via the syntax (! n :attr)
 622     */
 623   virtual void setUserAttribute(const std::string& attr, Node n, std::vector<Node> node_values, std::string str_value) {
 624     Unimplemented() << "Theory " << identify()
 625                     << " doesn't support Theory::setUserAttribute interface";
 626   }
 627
 628   /** A set of theories */
 629   typedef uint32_t Set;
 630
 631   /** A set of all theories */
 632   static const Set AllTheories = (1 << theory::THEORY_LAST) - 1;
 633
 634   /** Pops a first theory off the set */
 635   static inline TheoryId setPop(Set& set) {
 636     uint32_t i = ffs(set); // Find First Set (bit)
 637     if (i == 0) { return THEORY_LAST; }
 638     TheoryId id = (TheoryId)(i-1);
 639     set = setRemove(id, set);
 640     return id;
 641   }
 642
 643   /** Returns the size of a set of theories */
 644   static inline size_t setSize(Set set) {
 645     size_t count = 0;
 646     while (setPop(set) != THEORY_LAST) {
 647       ++ count;
 648     }
 649     return count;
 650   }
 651
 652   /** Returns the index size of a set of theories */
 653   static inline size_t setIndex(TheoryId id, Set set) {
 654     Assert(setContains(id, set));
 655     size_t count = 0;
 656     while (setPop(set) != id) {
 657       ++ count;
 658     }
 659     return count;
 660   }
 661
 662   /** Add the theory to the set. If no set specified, just returns a singleton set */
 663   static inline Set setInsert(TheoryId theory, Set set = 0) {
 664     return set | (1 << theory);
 665   }
 666
 667   /** Add the theory to the set. If no set specified, just returns a singleton set */
 668   static inline Set setRemove(TheoryId theory, Set set = 0) {
 669     return setDifference(set, setInsert(theory));
 670   }
 671
 672   /** Check if the set contains the theory */
 673   static inline bool setContains(TheoryId theory, Set set) {
 674     return set & (1 << theory);
 675   }
 676
 677   static inline Set setComplement(Set a) {
 678     return (~a) & AllTheories;
 679   }
 680
 681   static inline Set setIntersection(Set a, Set b) {
 682     return a & b;
 683   }
 684
 685   static inline Set setUnion(Set a, Set b) {
 686     return a | b;
 687   }
 688
 689   /** a - b  */
 690   static inline Set setDifference(Set a, Set b) {
 691     return (~b) & a;
 692   }
 693
 694   static inline std::string setToString(theory::Theory::Set theorySet) {
 695     std::stringstream ss;
 696     ss << "[";
 697     for(unsigned theoryId = 0; theoryId < theory::THEORY_LAST; ++theoryId) {
 698       if (theory::Theory::setContains((theory::TheoryId)theoryId, theorySet)) {
 699         ss << (theory::TheoryId) theoryId << " ";
 700       }
 701     }
 702     ss << "]";
 703     return ss.str();
 704   }
 705
 706   typedef context::CDList<Assertion>::const_iterator assertions_iterator;
 707
 708   /**
 709    * Provides access to the facts queue, primarily intended for theory
 710    * debugging purposes.
 711    *
 712    * @return the iterator to the beginning of the fact queue
 713    */
 714   assertions_iterator facts_begin() const {
 715     return d_facts.begin();
 716   }
 717
 718   /**
 719    * Provides access to the facts queue, primarily intended for theory
 720    * debugging purposes.
 721    *
 722    * @return the iterator to the end of the fact queue
 723    */
 724   assertions_iterator facts_end() const {
 725     return d_facts.end();
 726   }
 727   /**
 728    * Whether facts have been asserted to this theory.
 729    *
 730    * @return true iff facts have been asserted to this theory.
 731    */
 732   bool hasFacts() {
 733     return !d_facts.empty();
 734   }
 735
 736   /** Return total number of facts asserted to this theory */
 737   size_t numAssertions() {
 738     return d_facts.size();
 739   }
 740
 741   typedef context::CDList<TNode>::const_iterator shared_terms_iterator;
 742
 743   /**
 744    * Provides access to the shared terms, primarily intended for theory
 745    * debugging purposes.
 746    *
 747    * @return the iterator to the beginning of the shared terms list
 748    */
 749   shared_terms_iterator shared_terms_begin() const {
 750     return d_sharedTerms.begin();
 751   }
 752
 753   /**
 754    * Provides access to the facts queue, primarily intended for theory
 755    * debugging purposes.
 756    *
 757    * @return the iterator to the end of the shared terms list
 758    */
 759   shared_terms_iterator shared_terms_end() const {
 760     return d_sharedTerms.end();
 761   }
 762
 763
 764   /**
 765    * This is a utility function for constructing a copy of the currently shared terms
 766    * in a queriable form.  As this is
 767    */
 768   std::unordered_set<TNode, TNodeHashFunction> currentlySharedTerms() const;
 769
 770   /**
 771    * This allows the theory to be queried for whether a literal, lit, is
 772    * entailed by the theory.  This returns a pair of a Boolean and a node E.
 773    *
 774    * If the Boolean is true, then E is a formula that entails lit and E is propositionally
 775    * entailed by the assertions to the theory.
 776    *
 777    * If the Boolean is false, it is "unknown" if lit is entailed and E may be
 778    * any node.
 779    *
 780    * The literal lit is either an atom a or (not a), which must belong to the theory:
 781    *   There is some TheoryOfMode m s.t. Theory::theoryOf(m, a) == this->getId().
 782    *
 783    * There are NO assumptions that a or the subterms of a have been
 784    * preprocessed in any form.  This includes ppRewrite, rewriting,
 785    * preregistering, registering, definition expansion or ITE removal!
 786    *
 787    * Theories are free to limit the amount of effort they use and so may
 788    * always opt to return "unknown".  Both "unknown" and "not entailed",
 789    * may return for E a non-boolean Node (e.g. Node::null()).  (There is no explicit output
 790    * for the negation of lit is entailed.)
 791    *
 792    * If lit is theory valid, the return result may be the Boolean constant
 793    * true for E.
 794    *
 795    * If lit is entailed by multiple assertions on the theory's getFact()
 796    * queue, a_1, a_2, ... and a_k, this may return E=(and a_1 a_2 ... a_k) or
 797    * another theory entailed explanation E=(and (and a_1 a_2) (and a3 a_4) ... a_k)
 798    *
 799    * If lit is entailed by a single assertion on the theory's getFact()
 800    * queue, say a, this may return E=a.
 801    *
 802    * The theory may always return false!
 803    *
 804    * The search is controlled by the parameter params.  For default behavior,
 805    * this may be left NULL.
 806    *
 807    * Theories that want parameters extend the virtual EntailmentCheckParameters
 808    * class.  Users ask the theory for an appropriate subclass from the theory
 809    * and configure that.  How this is implemented is on a per theory basis.
 810    *
 811    * The search may provide additional output to guide the user of
 812    * this function.  This output is stored in a EntailmentCheckSideEffects*
 813    * output parameter.  The implementation of this is theory specific.  For
 814    * no output, this is NULL.
 815    *
 816    * Theories may not touch their output stream during an entailment check.
 817    *
 818    * @param  lit     a literal belonging to the theory.
 819    * @param  params  the control parameters for the entailment check.
 820    * @param  out     a theory specific output object of the entailment search.
 821    * @return         a pair <b,E> s.t. if b is true, then a formula E such that
 822    * E |= lit in the theory.
 823    */
 824   virtual std::pair<bool, Node> entailmentCheck(
 825       TNode lit, const EntailmentCheckParameters* params = NULL,
 826       EntailmentCheckSideEffects* out = NULL);
 827
 828   /* equality engine TODO: use? */
 829   virtual eq::EqualityEngine* getEqualityEngine() { return NULL; }
 830
 831   /* Get extended theory if one has been installed. */
 832   ExtTheory* getExtTheory();
 833
 834   /* get current substitution at an effort
 835    *   input : vars
 836    *   output : subs, exp
 837    *   where ( exp[vars[i]] => vars[i] = subs[i] ) holds for all i
 838    */
 839   virtual bool getCurrentSubstitution(int effort, std::vector<Node>& vars,
 840                                       std::vector<Node>& subs,
 841                                       std::map<Node, std::vector<Node> >& exp) {
 842     return false;
 843   }
 844
 845   /* is extended function reduced */
 846   virtual bool isExtfReduced( int effort, Node n, Node on, std::vector< Node >& exp ) { return n.isConst(); }
 847
 848   /**
 849    * Get reduction for node
 850    * If return value is not 0, then n is reduced.
 851    * If return value <0 then n is reduced SAT-context-independently (e.g. by a
 852    *  lemma that persists at this user-context level).
 853    * If nr is non-null, then ( n = nr ) should be added as a lemma by caller,
 854    *  and return value should be <0.
 855    */
 856   virtual int getReduction( int effort, Node n, Node& nr ) { return 0; }
 857
 858   /** Turn on proof-production mode. */
 859   void produceProofs() { d_proofsEnabled = true; }
 860
 861 };/* class Theory */
 862
 863 std::ostream& operator<<(std::ostream& os, theory::Theory::Effort level);
 864
 865
 866 inline theory::Assertion Theory::get() {
 867   Assert(!done()) << "Theory::get() called with assertion queue empty!";
 868
 869   // Get the assertion
 870   Assertion fact = d_facts[d_factsHead];
 871   d_factsHead = d_factsHead + 1;
 872
 873   Trace("theory") << "Theory::get() => " << fact << " (" << d_facts.size() - d_factsHead << " left)" << std::endl;
 874
 875   if(Dump.isOn("state")) {
 876     Dump("state") << AssertCommand(fact.d_assertion.toExpr());
 877   }
 878
 879   return fact;
 880 }
 881
 882 inline std::ostream& operator<<(std::ostream& out,
 883                                 const CVC4::theory::Theory& theory) {
 884   return out << theory.identify();
 885 }
 886
 887 inline std::ostream& operator << (std::ostream& out, theory::Theory::PPAssertStatus status) {
 888   switch (status) {
 889   case theory::Theory::PP_ASSERT_STATUS_SOLVED:
 890     out << "SOLVE_STATUS_SOLVED"; break;
 891   case theory::Theory::PP_ASSERT_STATUS_UNSOLVED:
 892     out << "SOLVE_STATUS_UNSOLVED"; break;
 893   case theory::Theory::PP_ASSERT_STATUS_CONFLICT:
 894     out << "SOLVE_STATUS_CONFLICT"; break;
 895   default:
 896     Unhandled();
 897   }
 898   return out;
 899 }
 900
 901 class EntailmentCheckParameters {
 902 private:
 903   TheoryId d_tid;
 904 protected:
 905   EntailmentCheckParameters(TheoryId tid);
 906 public:
 907   TheoryId getTheoryId() const;
 908   virtual ~EntailmentCheckParameters();
 909 };/* class EntailmentCheckParameters */
 910
 911 class EntailmentCheckSideEffects {
 912 private:
 913   TheoryId d_tid;
 914 protected:
 915   EntailmentCheckSideEffects(TheoryId tid);
 916 public:
 917   TheoryId getTheoryId() const;
 918   virtual ~EntailmentCheckSideEffects();
 919 };/* class EntailmentCheckSideEffects */
 920
 921 }/* CVC4::theory namespace */
 922 }/* CVC4 namespace */
 923
 924 #endif /* CVC4__THEORY__THEORY_H */