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       1                 :            : /******************************************************************************
       2                 :            :  * This file is part of the cvc5 project.
       3                 :            :  *
       4                 :            :  * Copyright (c) 2009-2026 by the authors listed in the file AUTHORS
       5                 :            :  * in the top-level source directory and their institutional affiliations.
       6                 :            :  * All rights reserved.  See the file COPYING in the top-level source
       7                 :            :  * directory for licensing information.
       8                 :            :  * ****************************************************************************
       9                 :            :  *
      10                 :            :  * Regular expression solver for the theory of strings.
      11                 :            :  */
      12                 :            : 
      13                 :            : #include "cvc5_private.h"
      14                 :            : 
      15                 :            : #ifndef CVC5__THEORY__STRINGS__REGEXP_SOLVER_H
      16                 :            : #define CVC5__THEORY__STRINGS__REGEXP_SOLVER_H
      17                 :            : 
      18                 :            : #include <map>
      19                 :            : 
      20                 :            : #include "context/cdhashset.h"
      21                 :            : #include "context/cdlist.h"
      22                 :            : #include "context/context.h"
      23                 :            : #include "expr/node.h"
      24                 :            : #include "smt/env_obj.h"
      25                 :            : #include "theory/strings/extf_solver.h"
      26                 :            : #include "theory/strings/inference_manager.h"
      27                 :            : #include "theory/strings/regexp_operation.h"
      28                 :            : #include "theory/strings/sequences_stats.h"
      29                 :            : #include "theory/strings/skolem_cache.h"
      30                 :            : #include "theory/strings/solver_state.h"
      31                 :            : #include "theory/strings/term_registry.h"
      32                 :            : #include "util/string.h"
      33                 :            : 
      34                 :            : namespace cvc5::internal {
      35                 :            : namespace theory {
      36                 :            : namespace strings {
      37                 :            : 
      38                 :            : class RegExpSolver : protected EnvObj
      39                 :            : {
      40                 :            :   typedef context::CDList<Node> NodeList;
      41                 :            :   typedef context::CDHashMap<Node, bool> NodeBoolMap;
      42                 :            :   typedef context::CDHashMap<Node, int> NodeIntMap;
      43                 :            :   typedef context::CDHashMap<Node, unsigned> NodeUIntMap;
      44                 :            :   typedef context::CDHashMap<Node, Node> NodeNodeMap;
      45                 :            :   typedef context::CDHashSet<Node> NodeSet;
      46                 :            : 
      47                 :            :  public:
      48                 :            :   RegExpSolver(Env& env,
      49                 :            :                SolverState& s,
      50                 :            :                InferenceManager& im,
      51                 :            :                TermRegistry& tr,
      52                 :            :                CoreSolver& cs,
      53                 :            :                ExtfSolver& es,
      54                 :            :                SequencesStatistics& stats);
      55                 :      50707 :   ~RegExpSolver() {}
      56                 :            : 
      57                 :            :   /** check regular expression memberships
      58                 :            :    *
      59                 :            :    * This checks the satisfiability of all regular expression memberships
      60                 :            :    * of the form (not) s in R. We use various heuristic techniques based on
      61                 :            :    * unrolling, combined with techniques from Liang et al, "A Decision Procedure
      62                 :            :    * for Regular Membership and Length Constraints over Unbounded Strings",
      63                 :            :    * FroCoS 2015.
      64                 :            :    */
      65                 :            :   void checkMemberships(Theory::Effort e);
      66                 :            :   /**
      67                 :            :    * Check regular expression memberships eagerly, before running the CAV 14
      68                 :            :    * procedure for word equations. Adds lemmas based on our strategy involving
      69                 :            :    * reductions or simplifications.
      70                 :            :    */
      71                 :            :   void checkMembershipsEager();
      72                 :            : 
      73                 :            :  private:
      74                 :            :   /** compute asserted memberships, store in d_assertedMems */
      75                 :            :   void computeAssertedMemberships();
      76                 :            :   /** Compute active extended terms of kind k, grouped by representative. */
      77                 :            :   std::map<Node, std::vector<Node>> computeAssertions(Kind k) const;
      78                 :            :   /**
      79                 :            :    * Check inclusions,
      80                 :            :    * Assumes d_assertedMems has been computed.
      81                 :            :    */
      82                 :            :   void checkInclusions();
      83                 :            :   /**
      84                 :            :    * Check evaluations, which applies substitutions for normal forms to
      85                 :            :    * regular expression memberships and evaluates them, and also calls
      86                 :            :    * other methods (e.g. partial derivative computations) for the purposes
      87                 :            :    * of discovering conflictx.
      88                 :            :    * Assumes d_assertedMems has been computed.
      89                 :            :    */
      90                 :            :   void checkEvaluations();
      91                 :            :   /**
      92                 :            :    * Check unfold, which unfolds regular expression memberships based on the
      93                 :            :    * effort level.
      94                 :            :    * Assumes d_assertedMems has been computed.
      95                 :            :    */
      96                 :            :   void checkUnfold(Theory::Effort effort);
      97                 :            :   /**
      98                 :            :    * Check memberships in equivalence class for regular expression
      99                 :            :    * inclusion.
     100                 :            :    *
     101                 :            :    * This method returns false if it discovered a conflict for this set of
     102                 :            :    * assertions, and true otherwise. It discovers a conflict e.g. if mems
     103                 :            :    * contains str.in.re(xi, Ri) and ~str.in.re(xj, Rj) and Rj includes Ri.
     104                 :            :    *
     105                 :            :    * @param mems Vector of memberships of the form: (~)str.in.re(x1, R1)
     106                 :            :    *             ... (~)str.in.re(xn, Rn) where x1 = ... = xn in the
     107                 :            :    *             current context. The function removes elements from this
     108                 :            :    *             vector that were marked as reduced.
     109                 :            :    * @return False if a conflict was detected, true otherwise
     110                 :            :    */
     111                 :            :   bool checkEqcInclusion(std::vector<Node>& mems);
     112                 :            : 
     113                 :            :   /**
     114                 :            :    * Check memberships for equivalence class.
     115                 :            :    * The vector mems is a vector of memberships of the form:
     116                 :            :    *   (~) (x1 in R1 ) ... (~) (xn in Rn)
     117                 :            :    * where x1 = ... = xn in the current context.
     118                 :            :    *
     119                 :            :    * This method may add lemmas or conflicts via the inference manager.
     120                 :            :    *
     121                 :            :    * This method returns false if it discovered a conflict for this set of
     122                 :            :    * assertions, and true otherwise. It discovers a conflict e.g. if mems
     123                 :            :    * contains (xi in Ri) and (xj in Rj) and intersect(xi,xj) is empty.
     124                 :            :    */
     125                 :            :   bool checkEqcIntersect(const std::vector<Node>& mems);
     126                 :            :   /**
     127                 :            :    * Return true if we should process regular expression unfoldings with
     128                 :            :    * the given polarity at the given effort.
     129                 :            :    */
     130                 :            :   bool shouldUnfold(Theory::Effort e, bool pol) const;
     131                 :            :   /**
     132                 :            :    * Add the unfolding lemma for asserted regular expression membership
     133                 :            :    * assertion. Return true if a lemma was successfully sent to the inference
     134                 :            :    * manager.
     135                 :            :    */
     136                 :            :   bool doUnfold(const Node& assertion);
     137                 :            :   // Constants
     138                 :            :   Node d_emptyString;
     139                 :            :   Node d_emptyRegexp;
     140                 :            :   Node d_true;
     141                 :            :   Node d_false;
     142                 :            :   /** The solver state of the parent of this object */
     143                 :            :   SolverState& d_state;
     144                 :            :   /** the output channel of the parent of this object */
     145                 :            :   InferenceManager& d_im;
     146                 :            :   /** reference to the core solver, used for certain queries */
     147                 :            :   CoreSolver& d_csolver;
     148                 :            :   /** reference to the extended function solver of the parent */
     149                 :            :   ExtfSolver& d_esolver;
     150                 :            :   /** Reference to the statistics for the theory of strings/sequences. */
     151                 :            :   SequencesStatistics& d_statistics;
     152                 :            :   /**
     153                 :            :    * Check partial derivative
     154                 :            :    *
     155                 :            :    * Returns false if a lemma pertaining to checking the partial derivative
     156                 :            :    * of x in r was added. In this case, addedLemma is updated to true.
     157                 :            :    *
     158                 :            :    * The argument atom is the assertion that explains x in r, which is the
     159                 :            :    * normalized form of atom that may be modified using a substitution whose
     160                 :            :    * explanation is nf_exp.
     161                 :            :    */
     162                 :            :   bool checkPDerivative(Node x, Node r, Node atom, std::vector<Node>& nf_exp);
     163                 :            :   cvc5::internal::String getHeadConst(Node x);
     164                 :            :   bool deriveRegExp(Node x, Node r, Node atom, std::vector<Node>& ant);
     165                 :            :   Node getNormalSymRegExp(Node r, std::vector<Node>& nf_exp);
     166                 :            :   /** regular expression operation module */
     167                 :            :   RegExpOpr d_regexp_opr;
     168                 :            :   /** Asserted memberships, cached during a full effort check */
     169                 :            :   std::map<Node, std::vector<Node>> d_assertedMems;
     170                 :            : }; /* class TheoryStrings */
     171                 :            : 
     172                 :            : }  // namespace strings
     173                 :            : }  // namespace theory
     174                 :            : }  // namespace cvc5::internal
     175                 :            : 
     176                 :            : #endif /* CVC5__THEORY__STRINGS__THEORY_STRINGS_H */