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/********************* */
/*! \file operator_elim.h
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 project.
** Copyright (c) 2009-2019 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 Operator elimination for arithmetic
**/
#pragma once
#include <map>
#include "expr/node.h"
#include "theory/logic_info.h"
namespace CVC4 {
namespace theory {
namespace arith {
class OperatorElim
{
public:
OperatorElim(const LogicInfo& info);
~OperatorElim() {}
/**
* Eliminate operators in term n. If n has top symbol that is not a core
* one (including division, int division, mod, to_int, is_int, syntactic sugar
* transcendental functions), then we replace it by a form that eliminates
* that operator. This may involve the introduction of witness terms.
*
* One exception to the above rule is that we may leave certain applications
* like (/ 4 1) unchanged, since replacing this by 4 changes its type from
* real to int. This is important for some subtyping issues during
* expandDefinition. Moreover, applications like this can be eliminated
* trivially later by rewriting.
*
* This method is called both during expandDefinition and during ppRewrite.
*
* @param n The node to eliminate operators from.
* @return The (single step) eliminated form of n.
*/
Node eliminateOperators(Node n);
/**
* Recursively ensure that n has no non-standard operators. This applies
* the above method on all subterms of n.
*
* @param n The node to eliminate operators from.
* @return The eliminated form of n.
*/
Node eliminateOperatorsRec(Node n);
private:
/** Logic info of the owner of this class */
const LogicInfo& d_info;
/**
* Maps for Skolems for to-integer, real/integer div-by-k, and inverse
* non-linear operators that are introduced during ppRewriteTerms.
*/
std::map<Node, Node> d_to_int_skolem;
std::map<Node, Node> d_div_skolem;
std::map<Node, Node> d_int_div_skolem;
std::map<Node, Node> d_nlin_inverse_skolem;
/** Arithmetic skolem identifier */
enum class ArithSkolemId
{
/* an uninterpreted function f s.t. f(x) = x / 0.0 (real division) */
DIV_BY_ZERO,
/* an uninterpreted function f s.t. f(x) = x / 0 (integer division) */
INT_DIV_BY_ZERO,
/* an uninterpreted function f s.t. f(x) = x mod 0 */
MOD_BY_ZERO,
/* an uninterpreted function f s.t. f(x) = sqrt(x) */
SQRT,
};
/**
* Function symbols used to implement:
* (1) Uninterpreted division-by-zero semantics. Needed to deal with partial
* division function ("/"),
* (2) Uninterpreted int-division-by-zero semantics. Needed to deal with
* partial function "div",
* (3) Uninterpreted mod-zero semantics. Needed to deal with partial
* function "mod".
*
* If the option arithNoPartialFun() is enabled, then the range of this map
* stores Skolem constants instead of Skolem functions, meaning that the
* function-ness of e.g. division by zero is ignored.
*/
std::map<ArithSkolemId, Node> d_arith_skolem;
/** get arithmetic skolem
*
* Returns the Skolem in the above map for the given id, creating it if it
* does not already exist.
*/
Node getArithSkolem(ArithSkolemId asi);
/** get arithmetic skolem application
*
* By default, this returns the term f( n ), where f is the Skolem function
* for the identifier asi.
*
* If the option arithNoPartialFun is enabled, this returns f, where f is
* the Skolem constant for the identifier asi.
*/
Node getArithSkolemApp(Node n, ArithSkolemId asi);
/**
* Called when a non-linear term n is given to this class. Throw an exception
* if the logic is linear.
*/
void checkNonLinearLogic(Node term);
};
} // namespace arith
} // namespace theory
} // namespace CVC4
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