src/theory/theory_proof_step_buffer.h

   1 /*********************                                                        */
   2 /*! \file theory_proof_step_buffer.h
   3  ** \verbatim
   4  ** Top contributors (to current version):
   5  **   Andrew Reynolds, Haniel Barbosa
   6  ** This file is part of the CVC4 project.
   7  ** Copyright (c) 2009-2020 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 Theory proof step buffer utility.
  13  **/
  14
  15 #include "cvc4_private.h"
  16
  17 #ifndef CVC4__THEORY__THEORY_PROOF_STEP_BUFFER_H
  18 #define CVC4__THEORY__THEORY_PROOF_STEP_BUFFER_H
  19
  20 #include <vector>
  21
  22 #include "expr/node.h"
  23 #include "expr/proof_step_buffer.h"
  24 #include "theory/builtin/proof_checker.h"
  25
  26 namespace CVC4 {
  27 namespace theory {
  28 /**
  29  * Class used to speculatively try and buffer a set of proof steps before
  30  * sending them to a proof object, extended with theory-specfic proof rule
  31  * utilities.
  32  */
  33 class TheoryProofStepBuffer : public ProofStepBuffer
  34 {
  35  public:
  36   TheoryProofStepBuffer(ProofChecker* pc = nullptr);
  37   ~TheoryProofStepBuffer() {}
  38   //---------------------------- utilities builtin proof rules
  39   /**
  40    * Apply equality introduction. If this method returns true, it adds proof
  41    * step(s) to the buffer that conclude (= src tgt) from premises exp. In
  42    * particular, it may attempt to apply the rule MACRO_SR_EQ_INTRO. This
  43    * method should be applied when tgt is equivalent to src assuming exp.
  44    */
  45   bool applyEqIntro(Node src,
  46                     Node tgt,
  47                     const std::vector<Node>& exp,
  48                     MethodId ids = MethodId::SB_DEFAULT,
  49                     MethodId idr = MethodId::RW_REWRITE);
  50   /**
  51    * Apply predicate transform. If this method returns true, it adds (at most
  52    * one) proof step to the buffer that conclude tgt from premises src, exp. In
  53    * particular, it may attempt to apply MACRO_SR_PRED_TRANSFORM. This method
  54    * should be applied when src and tgt are equivalent formulas assuming exp.
  55    */
  56   bool applyPredTransform(Node src,
  57                           Node tgt,
  58                           const std::vector<Node>& exp,
  59                           MethodId ids = MethodId::SB_DEFAULT,
  60                           MethodId idr = MethodId::RW_REWRITE);
  61   /**
  62    * Apply predicate introduction. If this method returns true, it adds proof
  63    * step(s) to the buffer that conclude tgt from premises exp. In particular,
  64    * it may attempt to apply the rule MACRO_SR_PRED_INTRO. This method should be
  65    * applied when tgt is equivalent to true assuming exp.
  66    */
  67   bool applyPredIntro(Node tgt,
  68                       const std::vector<Node>& exp,
  69                       MethodId ids = MethodId::SB_DEFAULT,
  70                       MethodId idr = MethodId::RW_REWRITE);
  71   /**
  72    * Apply predicate elimination. This method returns the result of applying
  73    * the rule MACRO_SR_PRED_ELIM on src, exp. The returned formula is equivalent
  74    * to src assuming exp. If the return value is equivalent to src, then no
  75    * proof step is added to this buffer, since this step is a no-op in this
  76    * case.
  77    *
  78    * Notice that in contrast to the other rules above, predicate elimination
  79    * never fails and proves a formula that is not explicitly given as an
  80    * argument tgt. Thus, the return value of this method is Node not bool.
  81    */
  82   Node applyPredElim(Node src,
  83                      const std::vector<Node>& exp,
  84                      MethodId ids = MethodId::SB_DEFAULT,
  85                      MethodId idr = MethodId::RW_REWRITE);
  86   //---------------------------- end utilities builtin proof rules
  87
  88   //---------------------------- utility methods for normalizing clauses
  89   /**
  90    * Normalizes a non-unit clause (an OR node) according to factoring and
  91    * reordering, i.e. removes duplicates and reorders literals (according to
  92    * node ids). Moreover it eliminates double negations, which can be done also
  93    * for unit clauses (a arbitrary Boolean node). All normalization steps are
  94    * tracked via proof steps added to this proof step buffer.
  95    *
  96    * @param n the clause to be normalized
  97    * @return the normalized clause node
  98    */
  99   Node factorReorderElimDoubleNeg(Node n);
 100
 101   /**
 102    * Eliminates double negation of a literal if it has the form
 103    *  (not (not t))
 104    * If the elimination happens, a step is added to this proof step buffer.
 105    *
 106    * @param n the node to have the top-level double negation eliminated
 107    * @return the normalized clause node
 108    */
 109   Node elimDoubleNegLit(Node n);
 110 };
 111
 112 }  // namespace theory
 113 }  // namespace CVC4
 114
 115 #endif /* CVC4__THEORY__THEORY_PROOF_STEP_BUFFER_H */