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/********************* */
/*! \file extended_rewrite.h
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 project.
** Copyright (c) 2009-2017 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 extended rewriting class
**/
#include "cvc4_private.h"
#ifndef __CVC4__THEORY__QUANTIFIERS__EXTENDED_REWRITE_H
#define __CVC4__THEORY__QUANTIFIERS__EXTENDED_REWRITE_H
#include <unordered_map>
#include "expr/node.h"
namespace CVC4 {
namespace theory {
namespace quantifiers {
/** Extended rewriter
*
* This class is used for all rewriting that is not necessarily
* helpful for quantifier-free solving, but is helpful
* in other use cases. An example of this is SyGuS, where rewriting
* can be used for generalizing refinement lemmas, and hence
* should be highly aggressive.
*
* This class extended the standard techniques for rewriting
* with techniques, including but not limited to:
* - ITE branch merging,
* - ITE conditional variable elimination,
* - ITE condition subsumption, and
* - Aggressive rewriting for string equalities.
*/
class ExtendedRewriter
{
public:
ExtendedRewriter(bool aggr = true);
~ExtendedRewriter() {}
/** return the extended rewritten form of n */
Node extendedRewrite(Node n);
private:
/**
* Whether this extended rewriter applies aggressive rewriting techniques,
* which are more expensive. Examples of aggressive rewriting include:
* - conditional rewriting,
* - condition merging,
* - sorting childing of commutative operators with more than 5 children.
*
* Aggressive rewriting is applied for SyGuS, whereas non-aggressive rewriting
* may be applied as a preprocessing step.
*/
bool d_aggr;
/** true and false nodes */
Node d_true;
Node d_false;
/** cache for extendedRewrite */
std::unordered_map<Node, Node, NodeHashFunction> d_ext_rewrite_cache;
/** pull ITE
* Do simple ITE pulling, e.g.:
* C2 --->^E false
* implies:
* ite( C, C1, C2 ) --->^E C ^ C1
* where ---->^E denotes extended rewriting.
*/
Node extendedRewritePullIte(Node n);
/** extended rewrite aggressive */
Node extendedRewriteAggr(Node n);
};
} /* CVC4::theory::quantifiers namespace */
} /* CVC4::theory namespace */
} /* CVC4 namespace */
#endif /* __CVC4__THEORY__QUANTIFIERS__EXTENDED_REWRITE_H */
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