/******************************************************************************

 * Top contributors (to current version):

 *   Andrew Reynolds, Mathias Preiner

 *

 * This file is part of the cvc5 project.

 *

 * Copyright (c) 2009-2021 by the authors listed in the file AUTHORS

 * in the top-level source directory and their institutional affiliations.

 * All rights reserved.  See the file COPYING in the top-level source

 * directory for licensing information.

 * ****************************************************************************

 *

 * Simple symmetry breaking for sygus.

 */

#include "cvc5_private.h"

#ifndef CVC5__THEORY__DATATYPES__SIMPLE_SYM_BREAK_H

#define CVC5__THEORY__DATATYPES__SIMPLE_SYM_BREAK_H

#include "expr/dtype.h"

#include "theory/quantifiers/sygus/term_database_sygus.h"

namespace cvc5 {

namespace theory {

namespace datatypes {

/** SygusSimpleSymBreak

 *

 * This class implements queries that can be queried statically about sygus

 * grammars, for example, concerning which constructors need not appear at

 * argument positions of others. This is used by the sygus extension of the

 * quantifier-free datatypes procedure for adding symmetry breaking lemmas.

 * We call this class of techniques "simple static symmetry breaking". These

 * techniques have the advantage over "dynamic symmetry breaking" (blocking

 * redundant solutions on demand in datatypes_sygus.h) in that we can design

 * efficient encodings of symmetry breaking constraints, whereas dynamic

 * symmetry breaking may in the worst case block solutions one by one.

 */

class SygusSimpleSymBreak

{

 public:

  SygusSimpleSymBreak(quantifiers::TermDbSygus* tds);

  /** consider argument kind

   *

   * This method returns false if the arg^th argument of terms of parent kind

   * pk need not be of kind k. The type tnp is the sygus type of type

   * containing pk, and tn is the sygus type of the arg^th argument of the

   * constructor whose builtin kind is pk.

   *

   * For example, given grammar:

   *   A -> A + A | 0 | 1 | x | -A

   * This method will return false for inputs such as:

   *   A, A, -, -, 0  (due to cancelling of double unary minus)

   *   A, A, +, +, 1  (due to commutativity of addition, we can assume all

   *                   nested + occurs in the 0^th argument)

   */

  bool considerArgKind(TypeNode tn, TypeNode tnp, Kind k, Kind pk, int arg);

  /** consider constant

   *

   * Similar to the above function, this method returns false if the arg^th

   * argument of terms of parent kind pk need not be the constant c. The type

   * tnp is the sygus type of type containing pk, and tn is the sygus type of

   * the arg^th argument of the constructor whose builtin kind is pk.

   *

   * For example, given grammar:

   *   A -> B * B | A + A | 0 | 1 | x | -A

   *   B -> 0 | x

   * This method will return false for inputs such as:

   *   A, A, 0, +, 0 (due to identity of addition with zero)

   *   B, A, 0, *, 0 (due to simplification 0*x --> 0, and 0 is generated by A)

   */

  bool considerConst(TypeNode tn, TypeNode tnp, Node c, Kind pk, int arg);

  /** solve for argument

   *

   * If this method returns a non-negative integer n, then all terms at

   * the arg^th position of the cindex^th constructor of sygus type tnp need

   * only be of the n^th constructor of that argument.

   *

   * For example, given grammar:

   *   A -> A - A | A + A | 0 | 1 | x | y

   * Say solveForArgument(A, 0, 0)=2. This indicates that all terms of the form

   * x1-x2 need only be such that x1 is 0.

   */

  int solveForArgument(TypeNode tnp, unsigned cindex, unsigned arg);

 private:

  /** Pointer to the sygus term database */

  quantifiers::TermDbSygus* d_tds;

  /** return the index of the first argument position of c that has type tn */

  int getFirstArgOccurrence(const DTypeConstructor& c, TypeNode tn);

  /**

   * Helper function for consider const above, pdt is the datatype of the type

   * of tnp.

   */

  bool considerConst(const DType& pdt, TypeNode tnp, Node c, Kind pk, int arg);

};

}  // namespace datatypes

}  // namespace theory

}  // namespace cvc5

#endif /* CVC5__THEORY__DATATYPES__SIMPLE_SYM_BREAK_H */