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/********************* */
/*! \file quant_elim_solver.h
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 project.
** Copyright (c) 2009-2020 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.\endverbatim
**
** \brief The solver for quantifier elimination queries
**/
#include "cvc4_private.h"
#ifndef CVC4__SMT__QUANT_ELIM_SOLVER_H
#define CVC4__SMT__QUANT_ELIM_SOLVER_H
#include "expr/node.h"
#include "smt/assertions.h"
namespace CVC4 {
namespace smt {
class SmtSolver;
/**
* A solver for quantifier elimination queries.
*
* This class is responsible for responding to get-qe and get-qe-partial
* commands. It uses an underlying SmtSolver, which it queries for
* quantifier instantiations used for unsat which are in turn used for
* constructing the solution for the quantifier elimination query.
*/
class QuantElimSolver
{
public:
QuantElimSolver(SmtSolver& sms);
~QuantElimSolver();
/**
* This function takes as input a quantified formula q
* of the form:
* Q x1...xn. P( x1...xn, y1...yn )
* where P( x1...xn, y1...yn ) is a quantifier-free
* formula in a logic that supports quantifier elimination.
* Currently, the only logics supported by quantifier
* elimination is LRA and LIA.
*
* This function returns a formula ret such that, given
* the current set of formulas A asserted to this SmtEngine :
*
* If doFull = true, then
* - ( A ^ q ) and ( A ^ ret ) are equivalent
* - ret is quantifier-free formula containing
* only free variables in y1...yn.
*
* If doFull = false, then
* - (A ^ q) => (A ^ ret) if Q is forall or
* (A ^ ret) => (A ^ q) if Q is exists,
* - ret is quantifier-free formula containing
* only free variables in y1...yn,
* - If Q is exists, let A^Q_n be the formula
* A ^ ~ret^Q_1 ^ ... ^ ~ret^Q_n
* where for each i=1,...n, formula ret^Q_i
* is the result of calling doQuantifierElimination
* for q with the set of assertions A^Q_{i-1}.
* Similarly, if Q is forall, then let A^Q_n be
* A ^ ret^Q_1 ^ ... ^ ret^Q_n
* where ret^Q_i is the same as above.
* In either case, we have that ret^Q_j will
* eventually be true or false, for some finite j.
*
* The former feature is quantifier elimination, and
* is run on invocations of the smt2 extended command get-qe.
* The latter feature is referred to as partial quantifier
* elimination, and is run on invocations of the smt2
* extended command get-qe-disjunct, which can be used
* for incrementally computing the result of a
* quantifier elimination.
*/
Node getQuantifierElimination(Assertions& as, Node q, bool doFull);
private:
/** The SMT solver, which is used during doQuantifierElimination. */
SmtSolver& d_smtSolver;
};
} // namespace smt
} // namespace CVC4
#endif /* CVC4__SMT__QUANT_ELIM_SOLVER_H */
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