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/********************* */
/*! \file skolem_cache.cpp
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** 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 Implementation of a cache of skolems for theory of strings.
**/
#include "theory/strings/skolem_cache.h"
#include "theory/rewriter.h"
#include "theory/strings/theory_strings.h"
#include "theory/strings/theory_strings_rewriter.h"
#include "util/rational.h"
using namespace CVC4::kind;
namespace CVC4 {
namespace theory {
namespace strings {
SkolemCache::SkolemCache(TheoryStrings* ts)
{
NodeManager* nm = NodeManager::currentNM();
d_ts = ts;
d_strType = nm->stringType();
d_zero = nm->mkConst(Rational(0));
}
Node SkolemCache::mkSkolemCached(Node a, Node b, SkolemId id, const char* c)
{
return mkTypedSkolemCached(d_strType, a, b, id, c);
}
Node SkolemCache::mkSkolemCached(Node a, SkolemId id, const char* c)
{
return mkSkolemCached(a, Node::null(), id, c);
}
Node SkolemCache::mkTypedSkolemCached(
TypeNode tn, Node a, Node b, SkolemId id, const char* c)
{
a = a.isNull() ? a : Rewriter::rewrite(a);
b = b.isNull() ? b : Rewriter::rewrite(b);
if (tn == d_strType)
{
std::tie(id, a, b) = normalizeStringSkolem(id, a, b);
}
std::map<SkolemId, Node>::iterator it = d_skolemCache[a][b].find(id);
if (it == d_skolemCache[a][b].end())
{
Node sk = mkTypedSkolem(tn, c);
d_skolemCache[a][b][id] = sk;
if (id == SK_FIRST_CTN_POST && a.getKind() == STRING_SUBSTR) {
NodeManager* nm = NodeManager::currentNM();
Node aLen = nm->mkNode(STRING_LENGTH, a[0]);
Node sum = nm->mkNode(PLUS, a[1], a[2]);
if (TheoryStringsRewriter::checkEntailArith(sum, aLen)) {
Node skLen = nm->mkNode(STRING_LENGTH, sk);
Node sk2Len = nm->mkNode(STRING_LENGTH, mkSkolemCached(a[0], b, SK_FIRST_CTN_POST, "foo"));
d_ts->sendLemma(nm->mkConst(true), nm->mkNode(GEQ, sk2Len, skLen), "foo");
}
}
return sk;
}
return it->second;
}
Node SkolemCache::mkTypedSkolemCached(TypeNode tn,
Node a,
SkolemId id,
const char* c)
{
return mkTypedSkolemCached(tn, a, Node::null(), id, c);
}
Node SkolemCache::mkSkolem(const char* c)
{
return mkTypedSkolem(d_strType, c);
}
Node SkolemCache::mkTypedSkolem(TypeNode tn, const char* c)
{
Node n = NodeManager::currentNM()->mkSkolem(c, tn, "string skolem");
d_allSkolems.insert(n);
return n;
}
bool SkolemCache::isSkolem(Node n) const
{
return d_allSkolems.find(n) != d_allSkolems.end();
}
std::tuple<SkolemCache::SkolemId, Node, Node>
SkolemCache::normalizeStringSkolem(SkolemId id, Node a, Node b)
{
Trace("skolem-cache") << "normalizeStringSkolem start: (" << id << ", " << a
<< ", " << b << ")" << std::endl;
NodeManager* nm = NodeManager::currentNM();
/*
if (id == SK_FIRST_CTN_POST)
{
// SK_FIRST_CTN_POST(x, y) --->
// SK_SUFFIX_REM(x, (+ (str.len SK_FIRST_CTN_PRE(x, y)) (str.len y)))
id = SK_SUFFIX_REM;
Node pre = mkSkolemCached(a, b, SK_FIRST_CTN_PRE, "pre");
b = Rewriter::rewrite(nm->mkNode(
PLUS, nm->mkNode(STRING_LENGTH, pre), nm->mkNode(STRING_LENGTH, b)));
}
*/
// SK_PURIFY(str.substr x 0 (str.indexof x y 0)) ---> SK_FIRST_CTN_PRE(x, y)
if (id == SK_PURIFY && a.getKind() == kind::STRING_SUBSTR)
{
Node s = a[0];
Node n = a[1];
Node m = a[2];
if (m.getKind() == kind::STRING_STRIDOF && m[0] == s)
{
if (n == d_zero && m[2] == d_zero)
{
id = SK_FIRST_CTN_PRE;
a = m[0];
b = m[1];
}
}
}
if (id == SK_FIRST_CTN_PRE)
{
// SK_FIRST_CTN_PRE((str.substr x 0 n), y) ---> SK_FIRST_CTN_PRE(x, y)
while (a.getKind() == kind::STRING_SUBSTR && a[1] == d_zero)
{
a = a[0];
}
}
Trace("skolem-cache") << "normalizeStringSkolem end: (" << id << ", " << a
<< ", " << b << ")" << std::endl;
return std::make_tuple(id, a, b);
}
} // namespace strings
} // namespace theory
} // namespace CVC4
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