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       1                 :            : /******************************************************************************
       2                 :            :  * Top contributors (to current version):
       3                 :            :  *   Andrew Reynolds
       4                 :            :  *
       5                 :            :  * This file is part of the cvc5 project.
       6                 :            :  *
       7                 :            :  * Copyright (c) 2009-2025 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.
      11                 :            :  * ****************************************************************************
      12                 :            :  *
      13                 :            :  * sygus_term_enumerator
      14                 :            :  */
      15                 :            : 
      16                 :            : #include "cvc5_private.h"
      17                 :            : 
      18                 :            : #ifndef CVC5__EXPR__SYGUS_TERM_ENUMERATOR_H
      19                 :            : #define CVC5__EXPR__SYGUS_TERM_ENUMERATOR_H
      20                 :            : 
      21                 :            : #include <unordered_set>
      22                 :            : 
      23                 :            : #include "expr/node.h"
      24                 :            : #include "expr/type_node.h"
      25                 :            : #include "smt/env_obj.h"
      26                 :            : 
      27                 :            : namespace cvc5::internal {
      28                 :            : 
      29                 :            : namespace theory::quantifiers {
      30                 :            : class SygusEnumerator;
      31                 :            : }
      32                 :            : /**
      33                 :            :  * A virtual callback for whether to consider terms in an enumeration.
      34                 :            :  */
      35                 :            : class SygusTermEnumeratorCallback
      36                 :            : {
      37                 :            :  public:
      38                 :       1525 :   SygusTermEnumeratorCallback() {}
      39                 :       1487 :   virtual ~SygusTermEnumeratorCallback() {}
      40                 :            :   /**
      41                 :            :    * Add term, return true if the term should be considered in the enumeration.
      42                 :            :    * Notice that returning false indicates that n should not be considered as a
      43                 :            :    * subterm of any other term in the enumeration.
      44                 :            :    *
      45                 :            :    * @param n The SyGuS term, which is a deep embedding of the next term to
      46                 :            :    * enumerate.
      47                 :            :    * @param bterms The (rewritten, builtin) terms we have already enumerated
      48                 :            :    * @return true if n should be considered in the enumeration.
      49                 :            :    */
      50                 :            :   virtual bool addTerm(const Node& n, std::unordered_set<Node>& bterms) = 0;
      51                 :            : };
      52                 :            : 
      53                 :            : /**
      54                 :            :  * SygusTermEnumerator
      55                 :            :  *
      56                 :            :  * This class is used for enumerating all terms of a sygus datatype type. At
      57                 :            :  * a high level, it is used as an alternative approach to sygus datatypes
      58                 :            :  * solver as a candidate generator in a synthesis loop. It filters terms based
      59                 :            :  * on redundancy criteria, for instance, it does not generate two terms that can
      60                 :            :  * be shown to be equivalent via rewriting. It enumerates terms whose deep
      61                 :            :  * embedding is considered in order of sygus term size
      62                 :            :  * (TermDb::getSygusTermSize).
      63                 :            :  *
      64                 :            :  * It also can be configured to enumerate sygus terms with free variables,
      65                 :            :  * (as opposed to variables bound in the formal arguments list of the
      66                 :            :  * function-to-synthesize), where each free variable appears in exactly one
      67                 :            :  * subterm. For grammar:
      68                 :            :  *   S -> 0 | 1 | x | S+S
      69                 :            :  * this enumerator will generate the stream:
      70                 :            :  *   z1, 0, 1, x, z1+z2, z1+1, 1+1 ...
      71                 :            :  * and so on, where z1 and z2 are variables of type Int. We call
      72                 :            :  * these "shapes". This feature can be enabled by setting enumShapes to true
      73                 :            :  * in the constructor below.
      74                 :            :  *
      75                 :            :  * In detail to generate all terms in a grammar:
      76                 :            :  *
      77                 :            :  *   SygusTermEnumerator enum(...);
      78                 :            :  *   std::vector<Node> terms;
      79                 :            :  *   do
      80                 :            :  *   {
      81                 :            :  *     terms.push_back(enum.getCurrent());
      82                 :            :  *   } while (enum.increment());
      83                 :            :  */
      84                 :            : class SygusTermEnumerator
      85                 :            : {
      86                 :            :  public:
      87                 :            :   /**
      88                 :            :    * @param env Reference to the environment
      89                 :            :    * @param tn The sygus datatype that encodes the grammar
      90                 :            :    * @param sec Pointer to an (optional) callback, required e.g. if we wish to
      91                 :            :    * do conjecture-specific symmetry breaking
      92                 :            :    * @param enumShapes If true, this enumerator will generate terms having any
      93                 :            :    * number of free variables
      94                 :            :    * @param enumAnyConstHoles If true, this enumerator will generate terms where
      95                 :            :    * free variables are the arguments to any-constant constructors.
      96                 :            :    * @param numConstants The number of interpreted constants to consider for
      97                 :            :    * each size in any-constant constructors.
      98                 :            :    */
      99                 :            :   SygusTermEnumerator(Env& env,
     100                 :            :                       const TypeNode& tn,
     101                 :            :                       SygusTermEnumeratorCallback* sec = nullptr,
     102                 :            :                       bool enumShapes = false,
     103                 :            :                       bool enumAnyConstHoles = false,
     104                 :            :                       size_t numConstants = 5);
     105                 :        136 :   ~SygusTermEnumerator() {}
     106                 :            :   /**
     107                 :            :    * Increment. If true, we ensure that getCurrent() is non-null. If false,
     108                 :            :    * there are no more terms in the enumeration.
     109                 :            :    */
     110                 :            :   bool increment();
     111                 :            :   /**
     112                 :            :    * Increment partial. Same as above but does not guarantee that getCurrent
     113                 :            :    * is non-null. This method can be used if the user wants the enumerator
     114                 :            :    * to not put too much effort into trying to enumerate the next value.
     115                 :            :    */
     116                 :            :   bool incrementPartial();
     117                 :            :   /**
     118                 :            :    * Get the current term generated by this class. This can be non-null
     119                 :            :    * prior to the first call to increment.
     120                 :            :    *
     121                 :            :    * In particular, this returns the builtin equivalent of the current sygus
     122                 :            :    * datatype term that was enumerated.
     123                 :            :    */
     124                 :            :   Node getCurrent();
     125                 :            : 
     126                 :            :  private:
     127                 :            :   /** The internal implementation */
     128                 :            :   std::unique_ptr<theory::quantifiers::SygusEnumerator> d_internal;
     129                 :            :   /** The enumerator, a dummy skolem passed to the above class */
     130                 :            :   Node d_enum;
     131                 :            : };
     132                 :            : 
     133                 :            : }  // namespace cvc5::internal
     134                 :            : 
     135                 :            : #endif /* CVC5__EXPR__SYGUS_TERM_ENUMERATOR_H */