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/********************* */
/*! \file bv_inverter.h
** \verbatim
** Top contributors (to current version):
** Mathias Preiner, Andrew Reynolds, Aina Niemetz
** This file is part of the CVC4 project.
** Copyright (c) 2009-2018 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 inverse rules for bit-vector operators
**/
#include "cvc4_private.h"
#ifndef __CVC4__BV_INVERTER_H
#define __CVC4__BV_INVERTER_H
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include "expr/node.h"
namespace CVC4 {
namespace theory {
namespace quantifiers {
/** BvInverterQuery
*
* This is a virtual class for queries
* required by the BvInverter class.
*/
class BvInverterQuery
{
public:
BvInverterQuery() {}
virtual ~BvInverterQuery() {}
/** returns the current model value of n */
virtual Node getModelValue(Node n) = 0;
/** returns a bound variable of type tn */
virtual Node getBoundVariable(TypeNode tn) = 0;
};
// inverter class
// TODO : move to theory/bv/ if generally useful?
class BvInverter
{
public:
BvInverter() {}
~BvInverter() {}
/** get dummy fresh variable of type tn, used as argument for sv */
Node getSolveVariable(TypeNode tn);
/**
* Get path to pv in lit, replace that occurrence by sv and all others by
* pvs (if pvs is non-null). If return value R is non-null, then :
* lit.path = pv R.path = sv
* R.path' = pvs for all lit.path' = pv, where path' != path
*/
Node getPathToPv(
Node lit, Node pv, Node sv, Node pvs, std::vector<unsigned>& path);
/**
* Same as above, but does not linearize lit for pv.
* Use this version if we know lit is linear wrt pv.
*/
Node getPathToPv(Node lit, Node pv, std::vector<unsigned>& path)
{
return getPathToPv(lit, pv, pv, Node::null(), path);
}
/** solveBvLit
*
* Solve for sv in lit, where lit.path = sv. If this function returns a
* non-null node t, then sv = t is the solved form of lit.
*
* If the BvInverterQuery provided to this function call is null, then
* the solution returned by this call will not contain CHOICE expressions.
* If the solved form for lit requires introducing a CHOICE expression,
* then this call will return null.
*/
Node solveBvLit(Node sv,
Node lit,
std::vector<unsigned>& path,
BvInverterQuery* m);
private:
/** Dummy variables for each type */
std::map<TypeNode, Node> d_solve_var;
/** Helper function for getPathToPv */
Node getPathToPv(Node lit,
Node pv,
Node sv,
std::vector<unsigned>& path,
std::unordered_set<TNode, TNodeHashFunction>& visited);
/** Helper function for getInv.
*
* This expects a condition cond where:
* (exists x. cond)
* is a BV tautology where x is getSolveVariable( tn ).
*
* It returns a term of the form:
* (choice y. cond { x -> y })
* where y is a bound variable and x is getSolveVariable( tn ).
*
* In some cases, we may return a term t if cond implies an equality on
* the solve variable. For example, if cond is x = t where x is
* getSolveVariable(tn), then we return t instead of introducing the choice
* function.
*
* This function will return the null node if the BvInverterQuery m provided
* to this call is null.
*/
Node getInversionNode(Node cond, TypeNode tn, BvInverterQuery* m);
};
} // namespace quantifiers
} // namespace theory
} // namespace CVC4
#endif /* __CVC4__BV_INVERTER_H */
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