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/********************* */
/*! \file theory_strings_preprocess.h
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds, Tianyi Liang, Mathias Preiner
** This file is part of the CVC4 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.\endverbatim
**
** \brief Strings Preprocess
**
** Strings Preprocess.
**/
#include "cvc4_private.h"
#ifndef CVC4__THEORY__STRINGS__PREPROCESS_H
#define CVC4__THEORY__STRINGS__PREPROCESS_H
#include <vector>
#include "context/cdhashmap.h"
#include "theory/rewriter.h"
#include "theory/strings/sequences_stats.h"
#include "theory/strings/skolem_cache.h"
#include "theory/theory.h"
#include "util/hash.h"
namespace CVC4 {
namespace theory {
namespace strings {
/** Strings preprocessor
*
* This class is responsible for extended function reductions. It is used as
* a preprocessor when --no-strings-lazy-pp is enabled. By default, it is
* used for reducing extended functions on-demand during the "extended function
* reductions" inference schema of TheoryStrings.
*/
class StringsPreprocess {
public:
StringsPreprocess(SkolemCache* sc,
IntegralHistogramStat<Kind>* statReductions = nullptr);
~StringsPreprocess();
/** The reduce routine
*
* This is the main routine for constructing the reduction lemma for
* an extended function t. It returns the simplified form of t, as well
* as assertions for t, interpeted conjunctively. The reduction lemma
* for t is:
* asserts[0] ^ ... ^ asserts[n] ^ t = t'
* where t' is the term returned by this method.
* The argument sc defines the methods for generating new Skolem variables.
* The return value is t itself if it is not reduced by this class.
*
* The reduction lemma for t is a way of specifying the complete semantics
* of t. In other words, any model satisfying the reduction lemma of t
* correctly interprets t.
*
* @param t The node to reduce,
* @param asserts The vector for storing the assertions that correspond to
* the reduction of t,
* @param sc The skolem cache for generating new variables,
* @return The reduced form of t.
*/
static Node reduce(Node t, std::vector<Node>& asserts, SkolemCache* sc);
/**
* Calls the above method for the skolem cache owned by this class, and
* records statistics.
*/
Node simplify(Node t, std::vector<Node>& asserts);
/**
* Applies simplifyRec on t until a fixed point is reached, and returns
* the resulting term t', which is such that
* (exists k) asserts => t = t'
* is valid, where k are the free skolems introduced when constructing
* asserts.
*/
Node processAssertion(Node t, std::vector<Node>& asserts);
private:
/** pointer to the skolem cache used by this class */
SkolemCache* d_sc;
/** Reference to the statistics for the theory of strings/sequences. */
IntegralHistogramStat<Kind>* d_statReductions;
/** visited cache */
std::map<Node, Node> d_visited;
/**
* Applies simplify to all top-level extended function subterms of t. New
* assertions created in this reduction are added to asserts. The argument
* visited stores a cache of previous results.
*/
Node simplifyRec(Node t, std::vector<Node>& asserts);
/**
* Make internal quantified formula with bound variable list bvl and body.
* Internally, we get a node corresponding to marking a quantified formula as
* an "internal" one. This node is provided as the third argument of the
* FORALL returned by this method. This ensures that E-matching is not applied
* to the quantified formula.
*/
static Node mkForallInternal(Node bvl, Node body);
};
}/* CVC4::theory::strings namespace */
}/* CVC4::theory namespace */
}/* CVC4 namespace */
#endif /* CVC4__THEORY__STRINGS__PREPROCESS_H */
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