Head

GCC Code Coverage Report

Directory:	.		Exec	Total	Coverage
File:	src/theory/strings/term_registry.cpp	Lines:	285	310	91.9 %
Date:	2021-09-15	Branches:	688	1422	48.4 %


/******************************************************************************
 * Top contributors (to current version):
 *   Andrew Reynolds, Andres Noetzli, Morgan Deters
 *
 * This file is part of the cvc5 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.
 * ****************************************************************************
 *
 * Implementation of term registry for the theory of strings.
 */

#include "theory/strings/term_registry.h"

#include "expr/attribute.h"
#include "options/smt_options.h"
#include "options/strings_options.h"
#include "smt/logic_exception.h"
#include "theory/rewriter.h"
#include "theory/strings/inference_manager.h"
#include "theory/strings/theory_strings_utils.h"
#include "theory/strings/word.h"
#include "util/rational.h"
#include "util/string.h"

using namespace std;
using namespace cvc5::context;
using namespace cvc5::kind;

namespace cvc5 {
namespace theory {
namespace strings {

struct StringsProxyVarAttributeId
{
};
typedef expr::Attribute<StringsProxyVarAttributeId, bool>
    StringsProxyVarAttribute;

TermRegistry::TermRegistry(Env& env,
                           SolverState& s,
                           SequencesStatistics& statistics,
                           ProofNodeManager* pnm)
    : EnvObj(env),
      d_state(s),
      d_im(nullptr),
      d_statistics(statistics),
      d_hasStrCode(false),
      d_functionsTerms(context()),
      d_inputVars(userContext()),
      d_preregisteredTerms(context()),
      d_registeredTerms(userContext()),
      d_registeredTypes(userContext()),
      d_proxyVar(userContext()),
      d_lengthLemmaTermsCache(userContext()),
      d_epg(
          pnm ? new EagerProofGenerator(
              pnm, userContext(), "strings::TermRegistry::EagerProofGenerator")
              : nullptr)
{
  NodeManager* nm = NodeManager::currentNM();
  d_zero = nm->mkConst(Rational(0));
  d_one = nm->mkConst(Rational(1));
  d_negOne = NodeManager::currentNM()->mkConst(Rational(-1));
  d_cardSize = utils::getAlphabetCardinality();
}

TermRegistry::~TermRegistry() {}

void TermRegistry::finishInit(InferenceManager* im) { d_im = im; }

Node TermRegistry::eagerReduce(Node t, SkolemCache* sc)
{
  NodeManager* nm = NodeManager::currentNM();
  Node lemma;
  Kind tk = t.getKind();
  if (tk == STRING_TO_CODE)
  {
    // ite( str.len(s)==1, 0 <= str.code(s) < |A|, str.code(s)=-1 )
    Node code_len = utils::mkNLength(t[0]).eqNode(nm->mkConst(Rational(1)));
    Node code_eq_neg1 = t.eqNode(nm->mkConst(Rational(-1)));
    Node code_range = nm->mkNode(
        AND,
        nm->mkNode(GEQ, t, nm->mkConst(Rational(0))),
        nm->mkNode(
            LT, t, nm->mkConst(Rational(utils::getAlphabetCardinality()))));
    lemma = nm->mkNode(ITE, code_len, code_range, code_eq_neg1);
  }
  else if (tk == STRING_INDEXOF || tk == STRING_INDEXOF_RE)
  {
    // (and
    //   (or (= (f x y n) (- 1)) (>= (f x y n) n))
    //   (<= (f x y n) (str.len x)))
    //
    // where f in { str.indexof, str.indexof_re }
    Node l = nm->mkNode(STRING_LENGTH, t[0]);
    lemma = nm->mkNode(
        AND,
        nm->mkNode(
            OR, nm->mkConst(Rational(-1)).eqNode(t), nm->mkNode(GEQ, t, t[2])),
        nm->mkNode(LEQ, t, l));
  }
  else if (tk == STRING_STOI)
  {
    // (>= (str.to_int x) (- 1))
    lemma = nm->mkNode(GEQ, t, nm->mkConst(Rational(-1)));
  }
  else if (tk == STRING_CONTAINS)
  {
    // ite( (str.contains s r), (= s (str.++ sk1 r sk2)), (not (= s r)))
    Node sk1 =
        sc->mkSkolemCached(t[0], t[1], SkolemCache::SK_FIRST_CTN_PRE, "sc1");
    Node sk2 =
        sc->mkSkolemCached(t[0], t[1], SkolemCache::SK_FIRST_CTN_POST, "sc2");
    lemma = t[0].eqNode(utils::mkNConcat(sk1, t[1], sk2));
    lemma = nm->mkNode(ITE, t, lemma, t[0].eqNode(t[1]).notNode());
  }
  return lemma;
}

Node TermRegistry::lengthPositive(Node t)
{
  NodeManager* nm = NodeManager::currentNM();
  Node zero = nm->mkConst(Rational(0));
  Node emp = Word::mkEmptyWord(t.getType());
  Node tlen = nm->mkNode(STRING_LENGTH, t);
  Node tlenEqZero = tlen.eqNode(zero);
  Node tEqEmp = t.eqNode(emp);
  Node caseEmpty = nm->mkNode(AND, tlenEqZero, tEqEmp);
  Node caseNEmpty = nm->mkNode(GT, tlen, zero);
  // (or (and (= (str.len t) 0) (= t "")) (> (str.len t) 0))
  return nm->mkNode(OR, caseEmpty, caseNEmpty);
}

void TermRegistry::preRegisterTerm(TNode n)
{
  if (d_preregisteredTerms.find(n) != d_preregisteredTerms.end())
  {
    return;
  }
  eq::EqualityEngine* ee = d_state.getEqualityEngine();
  d_preregisteredTerms.insert(n);
  Trace("strings-preregister")
      << "TheoryString::preregister : " << n << std::endl;
  // check for logic exceptions
  Kind k = n.getKind();
  if (!options::stringExp())
  {
    if (k == STRING_INDEXOF || k == STRING_INDEXOF_RE || k == STRING_ITOS
        || k == STRING_STOI || k == STRING_REPLACE || k == STRING_SUBSTR
        || k == STRING_REPLACE_ALL || k == SEQ_NTH || k == STRING_REPLACE_RE
        || k == STRING_REPLACE_RE_ALL || k == STRING_CONTAINS || k == STRING_LEQ
        || k == STRING_TOLOWER || k == STRING_TOUPPER || k == STRING_REV
        || k == STRING_UPDATE)
    {
      std::stringstream ss;
      ss << "Term of kind " << k
         << " not supported in default mode, try --strings-exp";
      throw LogicException(ss.str());
    }
  }
  if (k == EQUAL)
  {
    if (n[0].getType().isRegExp())
    {
      std::stringstream ss;
      ss << "Equality between regular expressions is not supported";
      throw LogicException(ss.str());
    }
    ee->addTriggerPredicate(n);
    return;
  }
  else if (k == STRING_IN_REGEXP)
  {
    d_im->requirePhase(n, true);
    ee->addTriggerPredicate(n);
    ee->addTerm(n[0]);
    ee->addTerm(n[1]);
    return;
  }
  else if (k == STRING_TO_CODE)
  {
    d_hasStrCode = true;
  }
  else if (k == REGEXP_RANGE)
  {
    for (const Node& nc : n)
    {
      if (!nc.isConst())
      {
        throw LogicException(
            "expecting a constant string term in regexp range");
      }
      if (nc.getConst<String>().size() != 1)
      {
        throw LogicException(
            "expecting a single constant string term in regexp range");
      }
    }
  }
  registerTerm(n, 0);
  TypeNode tn = n.getType();
  if (tn.isRegExp() && n.isVar())
  {
    std::stringstream ss;
    ss << "Regular expression variables are not supported.";
    throw LogicException(ss.str());
  }
  if (tn.isString())  // string-only
  {
    // all characters of constants should fall in the alphabet
    if (n.isConst())
    {
      std::vector<unsigned> vec = n.getConst<String>().getVec();
      for (unsigned u : vec)
      {
        if (u >= d_cardSize)
        {
          std::stringstream ss;
          ss << "Characters in string \"" << n
             << "\" are outside of the given alphabet.";
          throw LogicException(ss.str());
        }
      }
    }
    ee->addTerm(n);
  }
  else if (tn.isBoolean())
  {
    // All kinds that we do congruence over that may return a Boolean go here
    if (k == STRING_CONTAINS || k == STRING_LEQ || k == SEQ_NTH)
    {
      // Get triggered for both equal and dis-equal
      ee->addTriggerPredicate(n);
    }
  }
  else
  {
    // Function applications/predicates
    ee->addTerm(n);
  }
  // Set d_functionsTerms stores all function applications that are
  // relevant to theory combination. Notice that this is a subset of
  // the applications whose kinds are function kinds in the equality
  // engine. This means it does not include applications of operators
  // like re.++, which is not a function kind in the equality engine.
  // Concatenation terms do not need to be considered here because
  // their arguments have string type and do not introduce any shared
  // terms.
  if (n.hasOperator() && ee->isFunctionKind(k)
      && kindToTheoryId(k) == THEORY_STRINGS && k != STRING_CONCAT)
  {
    d_functionsTerms.push_back(n);
  }
  if (options::stringFMF())
  {
    if (tn.isStringLike())
    {
      // Our decision strategy will minimize the length of this term if it is a
      // variable but not an internally generated Skolem, or a term that does
      // not belong to this theory.
      if (n.isVar() ? !d_skCache.isSkolem(n)
                    : kindToTheoryId(k) != THEORY_STRINGS)
      {
        d_inputVars.insert(n);
        Trace("strings-preregister") << "input variable: " << n << std::endl;
      }
    }
  }
}

void TermRegistry::registerTerm(Node n, int effort)
{
  Trace("strings-register") << "TheoryStrings::registerTerm() " << n
                            << ", effort = " << effort << std::endl;
  if (d_registeredTerms.find(n) != d_registeredTerms.end())
  {
    Trace("strings-register") << "...already registered" << std::endl;
    return;
  }
  bool do_register = true;
  TypeNode tn = n.getType();
  if (!tn.isStringLike())
  {
    if (options::stringEagerLen())
    {
      do_register = effort == 0;
    }
    else
    {
      do_register = effort > 0 || n.getKind() != STRING_CONCAT;
    }
  }
  if (!do_register)
  {
    Trace("strings-register") << "...do not register" << std::endl;
    return;
  }
  Trace("strings-register") << "...register" << std::endl;
  d_registeredTerms.insert(n);
  // ensure the type is registered
  registerType(tn);
  TrustNode regTermLem;
  if (tn.isStringLike())
  {
    // register length information:
    //  for variables, split on empty vs positive length
    //  for concat/const/replace, introduce proxy var and state length relation
    regTermLem = getRegisterTermLemma(n);
  }
  else if (n.getKind() != STRING_CONTAINS)
  {
    // we don't send out eager reduction lemma for str.contains currently
    Node eagerRedLemma = eagerReduce(n, &d_skCache);
    if (!eagerRedLemma.isNull())
    {
      // if there was an eager reduction, we make the trust node for it
      if (d_epg != nullptr)
      {
        regTermLem = d_epg->mkTrustNode(
            eagerRedLemma, PfRule::STRING_EAGER_REDUCTION, {}, {n});
      }
      else
      {
        regTermLem = TrustNode::mkTrustLemma(eagerRedLemma, nullptr);
      }
    }
  }
  if (!regTermLem.isNull())
  {
    Trace("strings-lemma") << "Strings::Lemma REG-TERM : " << regTermLem
                           << std::endl;
    Trace("strings-assert")
        << "(assert " << regTermLem.getNode() << ")" << std::endl;
    d_im->trustedLemma(regTermLem, InferenceId::STRINGS_REGISTER_TERM);
  }
}

void TermRegistry::registerType(TypeNode tn)
{
  if (d_registeredTypes.find(tn) != d_registeredTypes.end())
  {
    return;
  }
  d_registeredTypes.insert(tn);
  if (tn.isStringLike())
  {
    // preregister the empty word for the type
    Node emp = Word::mkEmptyWord(tn);
    if (!d_state.hasTerm(emp))
    {
      preRegisterTerm(emp);
    }
  }
}

TrustNode TermRegistry::getRegisterTermLemma(Node n)
{
  Assert(n.getType().isStringLike());
  NodeManager* nm = NodeManager::currentNM();
  // register length information:
  //  for variables, split on empty vs positive length
  //  for concat/const/replace, introduce proxy var and state length relation
  Node lsum;
  if (n.getKind() != STRING_CONCAT && !n.isConst())
  {
    Node lsumb = nm->mkNode(STRING_LENGTH, n);
    lsum = Rewriter::rewrite(lsumb);
    // can register length term if it does not rewrite
    if (lsum == lsumb)
    {
      registerTermAtomic(n, LENGTH_SPLIT);
      return TrustNode::null();
    }
  }
  Node sk = d_skCache.mkSkolemCached(n, SkolemCache::SK_PURIFY, "lsym");
  StringsProxyVarAttribute spva;
  sk.setAttribute(spva, true);
  Node eq = Rewriter::rewrite(sk.eqNode(n));
  d_proxyVar[n] = sk;
  // If we are introducing a proxy for a constant or concat term, we do not
  // need to send lemmas about its length, since its length is already
  // implied.
  if (n.isConst() || n.getKind() == STRING_CONCAT)
  {
    // do not send length lemma for sk.
    registerTermAtomic(sk, LENGTH_IGNORE);
  }
  Node skl = nm->mkNode(STRING_LENGTH, sk);
  if (n.getKind() == STRING_CONCAT)
  {
    std::vector<Node> nodeVec;
    for (const Node& nc : n)
    {
      if (nc.getAttribute(StringsProxyVarAttribute()))
      {
        Assert(d_proxyVarToLength.find(nc) != d_proxyVarToLength.end());
        nodeVec.push_back(d_proxyVarToLength[nc]);
      }
      else
      {
        Node lni = nm->mkNode(STRING_LENGTH, nc);
        nodeVec.push_back(lni);
      }
    }
    lsum = nm->mkNode(PLUS, nodeVec);
    lsum = Rewriter::rewrite(lsum);
  }
  else if (n.isConst())
  {
    lsum = nm->mkConst(Rational(Word::getLength(n)));
  }
  Assert(!lsum.isNull());
  d_proxyVarToLength[sk] = lsum;
  Node ceq = Rewriter::rewrite(skl.eqNode(lsum));

  Node ret = nm->mkNode(AND, eq, ceq);

  // it is a simple rewrite to justify this
  if (d_epg != nullptr)
  {
    return d_epg->mkTrustNode(ret, PfRule::MACRO_SR_PRED_INTRO, {}, {ret});
  }
  return TrustNode::mkTrustLemma(ret, nullptr);
}

void TermRegistry::registerTermAtomic(Node n, LengthStatus s)
{
  if (d_lengthLemmaTermsCache.find(n) != d_lengthLemmaTermsCache.end())
  {
    return;
  }
  d_lengthLemmaTermsCache.insert(n);

  if (s == LENGTH_IGNORE)
  {
    // ignore it
    return;
  }
  std::map<Node, bool> reqPhase;
  TrustNode lenLem = getRegisterTermAtomicLemma(n, s, reqPhase);
  if (!lenLem.isNull())
  {
    Trace("strings-lemma") << "Strings::Lemma REGISTER-TERM-ATOMIC : " << lenLem
                           << std::endl;
    Trace("strings-assert")
        << "(assert " << lenLem.getNode() << ")" << std::endl;
    d_im->trustedLemma(lenLem, InferenceId::STRINGS_REGISTER_TERM_ATOMIC);
  }
  for (const std::pair<const Node, bool>& rp : reqPhase)
  {
    d_im->requirePhase(rp.first, rp.second);
  }
}

SkolemCache* TermRegistry::getSkolemCache() { return &d_skCache; }

const context::CDList<TNode>& TermRegistry::getFunctionTerms() const
{
  return d_functionsTerms;
}

const context::CDHashSet<Node>& TermRegistry::getInputVars() const
{
  return d_inputVars;
}

bool TermRegistry::hasStringCode() const { return d_hasStrCode; }

TrustNode TermRegistry::getRegisterTermAtomicLemma(
    Node n, LengthStatus s, std::map<Node, bool>& reqPhase)
{
  if (n.isConst())
  {
    // No need to send length for constant terms. This case may be triggered
    // for cases where the skolem cache automatically replaces a skolem by
    // a constant.
    return TrustNode::null();
  }
  Assert(n.getType().isStringLike());
  NodeManager* nm = NodeManager::currentNM();
  Node n_len = nm->mkNode(kind::STRING_LENGTH, n);
  Node emp = Word::mkEmptyWord(n.getType());
  if (s == LENGTH_GEQ_ONE)
  {
    Node neq_empty = n.eqNode(emp).negate();
    Node len_n_gt_z = nm->mkNode(GT, n_len, d_zero);
    Node len_geq_one = nm->mkNode(AND, neq_empty, len_n_gt_z);
    Trace("strings-lemma") << "Strings::Lemma SK-GEQ-ONE : " << len_geq_one
                           << std::endl;
    Trace("strings-assert") << "(assert " << len_geq_one << ")" << std::endl;
    return TrustNode::mkTrustLemma(len_geq_one, nullptr);
  }

  if (s == LENGTH_ONE)
  {
    Node len_one = n_len.eqNode(d_one);
    Trace("strings-lemma") << "Strings::Lemma SK-ONE : " << len_one
                           << std::endl;
    Trace("strings-assert") << "(assert " << len_one << ")" << std::endl;
    return TrustNode::mkTrustLemma(len_one, nullptr);
  }
  Assert(s == LENGTH_SPLIT);

  // get the positive length lemma
  Node lenLemma = lengthPositive(n);
  // split whether the string is empty
  Node n_len_eq_z = n_len.eqNode(d_zero);
  Node n_len_eq_z_2 = n.eqNode(emp);
  Node case_empty = nm->mkNode(AND, n_len_eq_z, n_len_eq_z_2);
  Node case_emptyr = Rewriter::rewrite(case_empty);
  if (!case_emptyr.isConst())
  {
    // prefer trying the empty case first
    // notice that requirePhase must only be called on rewritten literals that
    // occur in the CNF stream.
    n_len_eq_z = Rewriter::rewrite(n_len_eq_z);
    Assert(!n_len_eq_z.isConst());
    reqPhase[n_len_eq_z] = true;
    n_len_eq_z_2 = Rewriter::rewrite(n_len_eq_z_2);
    Assert(!n_len_eq_z_2.isConst());
    reqPhase[n_len_eq_z_2] = true;
  }
  else
  {
    // If n = "" ---> true or len( n ) = 0 ----> true, then we expect that
    // n ---> "". Since this method is only called on non-constants n, it must
    // be that n = "" ^ len( n ) = 0 does not rewrite to true.
    Assert(!case_emptyr.getConst<bool>());
  }

  if (d_epg != nullptr)
  {
    return d_epg->mkTrustNode(lenLemma, PfRule::STRING_LENGTH_POS, {}, {n});
  }
  return TrustNode::mkTrustLemma(lenLemma, nullptr);
}

Node TermRegistry::getSymbolicDefinition(Node n, std::vector<Node>& exp) const
{
  if (n.getNumChildren() == 0)
  {
    Node pn = getProxyVariableFor(n);
    if (pn.isNull())
    {
      return Node::null();
    }
    Node eq = n.eqNode(pn);
    eq = Rewriter::rewrite(eq);
    if (std::find(exp.begin(), exp.end(), eq) == exp.end())
    {
      exp.push_back(eq);
    }
    return pn;
  }
  std::vector<Node> children;
  if (n.getMetaKind() == metakind::PARAMETERIZED)
  {
    children.push_back(n.getOperator());
  }
  for (const Node& nc : n)
  {
    if (n.getType().isRegExp())
    {
      children.push_back(nc);
    }
    else
    {
      Node ns = getSymbolicDefinition(nc, exp);
      if (ns.isNull())
      {
        return Node::null();
      }
      else
      {
        children.push_back(ns);
      }
    }
  }
  return NodeManager::currentNM()->mkNode(n.getKind(), children);
}

Node TermRegistry::getProxyVariableFor(Node n) const
{
  NodeNodeMap::const_iterator it = d_proxyVar.find(n);
  if (it != d_proxyVar.end())
  {
    return (*it).second;
  }
  return Node::null();
}

Node TermRegistry::ensureProxyVariableFor(Node n)
{
  Node proxy = getProxyVariableFor(n);
  if (proxy.isNull())
  {
    registerTerm(n, 0);
    proxy = getProxyVariableFor(n);
  }
  Assert(!proxy.isNull());
  return proxy;
}

void TermRegistry::removeProxyEqs(Node n, std::vector<Node>& unproc) const
{
  if (n.getKind() == AND)
  {
    for (const Node& nc : n)
    {
      removeProxyEqs(nc, unproc);
    }
    return;
  }
  Trace("strings-subs-proxy") << "Input : " << n << std::endl;
  Node ns = Rewriter::rewrite(n);
  if (ns.getKind() == EQUAL)
  {
    for (size_t i = 0; i < 2; i++)
    {
      // determine whether this side has a proxy variable
      if (ns[i].getAttribute(StringsProxyVarAttribute()))
      {
        if (getProxyVariableFor(ns[1 - i]) == ns[i])
        {
          Trace("strings-subs-proxy")
              << "...trivial definition via " << ns[i] << std::endl;
          // it is a trivial equality, e.g. between a proxy variable
          // and its definition
          return;
        }
      }
    }
  }
  if (!n.isConst() || !n.getConst<bool>())
  {
    Trace("strings-subs-proxy") << "...unprocessed" << std::endl;
    unproc.push_back(n);
  }
}

}  // namespace strings
}  // namespace theory
}  // namespace cvc5


Generated by: GCOVR (Version 3.2)

Line	Exec	Source
1		/******************************************************************************
2		* Top contributors (to current version):
3		* Andrew Reynolds, Andres Noetzli, Morgan Deters
4		*
5		* This file is part of the cvc5 project.
6		*
7		* Copyright (c) 2009-2021 by the authors listed in the file AUTHORS
8		* in the top-level source directory and their institutional affiliations.
9		* All rights reserved. See the file COPYING in the top-level source
10		* directory for licensing information.
11		* ****************************************************************************
12		*
13		* Implementation of term registry for the theory of strings.
14		*/
15
16		#include "theory/strings/term_registry.h"
17
18		#include "expr/attribute.h"
19		#include "options/smt_options.h"
20		#include "options/strings_options.h"
21		#include "smt/logic_exception.h"
22		#include "theory/rewriter.h"
23		#include "theory/strings/inference_manager.h"
24		#include "theory/strings/theory_strings_utils.h"
25		#include "theory/strings/word.h"
26		#include "util/rational.h"
27		#include "util/string.h"
28
29		using namespace std;
30		using namespace cvc5::context;
31		using namespace cvc5::kind;
32
33		namespace cvc5 {
34		namespace theory {
35		namespace strings {
36
37		struct StringsProxyVarAttributeId
38		{
39		};
40		typedef expr::Attribute<StringsProxyVarAttributeId, bool>
41		StringsProxyVarAttribute;
42
43	9942	TermRegistry::TermRegistry(Env& env,
44		SolverState& s,
45		SequencesStatistics& statistics,
46	9942	ProofNodeManager* pnm)
47		: EnvObj(env),
48		d_state(s),
49		d_im(nullptr),
50		d_statistics(statistics),
51		d_hasStrCode(false),
52		d_functionsTerms(context()),
53	9942	d_inputVars(userContext()),
54		d_preregisteredTerms(context()),
55	9942	d_registeredTerms(userContext()),
56	9942	d_registeredTypes(userContext()),
57	9942	d_proxyVar(userContext()),
58	9942	d_lengthLemmaTermsCache(userContext()),
59		d_epg(
60		pnm ? new EagerProofGenerator(
61	2486	pnm, userContext(), "strings::TermRegistry::EagerProofGenerator")
62	62138	: nullptr)
63		{
64	9942	NodeManager* nm = NodeManager::currentNM();
65	9942	d_zero = nm->mkConst(Rational(0));
66	9942	d_one = nm->mkConst(Rational(1));
67	9942	d_negOne = NodeManager::currentNM()->mkConst(Rational(-1));
68	9942	d_cardSize = utils::getAlphabetCardinality();
69	9942	}
70
71	9939	TermRegistry::~TermRegistry() {}
72
73	9942	void TermRegistry::finishInit(InferenceManager* im) { d_im = im; }
74
75	30558	Node TermRegistry::eagerReduce(Node t, SkolemCache* sc)
76		{
77	30558	NodeManager* nm = NodeManager::currentNM();
78	30558	Node lemma;
79	30558	Kind tk = t.getKind();
80	30558	if (tk == STRING_TO_CODE)
81		{
82		// ite( str.len(s)==1, 0 <= str.code(s) < \|A\|, str.code(s)=-1 )
83	3322	Node code_len = utils::mkNLength(t[0]).eqNode(nm->mkConst(Rational(1)));
84	3322	Node code_eq_neg1 = t.eqNode(nm->mkConst(Rational(-1)));
85		Node code_range = nm->mkNode(
86		AND,
87	3322	nm->mkNode(GEQ, t, nm->mkConst(Rational(0))),
88	3322	nm->mkNode(
89	9966	LT, t, nm->mkConst(Rational(utils::getAlphabetCardinality()))));
90	1661	lemma = nm->mkNode(ITE, code_len, code_range, code_eq_neg1);
91		}
92	28897	else if (tk == STRING_INDEXOF \|\| tk == STRING_INDEXOF_RE)
93		{
94		// (and
95		// (or (= (f x y n) (- 1)) (>= (f x y n) n))
96		// (<= (f x y n) (str.len x)))
97		//
98		// where f in { str.indexof, str.indexof_re }
99	628	Node l = nm->mkNode(STRING_LENGTH, t[0]);
100	942	lemma = nm->mkNode(
101		AND,
102	1256	nm->mkNode(
103	1256	OR, nm->mkConst(Rational(-1)).eqNode(t), nm->mkNode(GEQ, t, t[2])),
104	942	nm->mkNode(LEQ, t, l));
105		}
106	28583	else if (tk == STRING_STOI)
107		{
108		// (>= (str.to_int x) (- 1))
109	91	lemma = nm->mkNode(GEQ, t, nm->mkConst(Rational(-1)));
110		}
111	28492	else if (tk == STRING_CONTAINS)
112		{
113		// ite( (str.contains s r), (= s (str.++ sk1 r sk2)), (not (= s r)))
114		Node sk1 =
115	8268	sc->mkSkolemCached(t[0], t[1], SkolemCache::SK_FIRST_CTN_PRE, "sc1");
116		Node sk2 =
117	8268	sc->mkSkolemCached(t[0], t[1], SkolemCache::SK_FIRST_CTN_POST, "sc2");
118	4134	lemma = t[0].eqNode(utils::mkNConcat(sk1, t[1], sk2));
119	4134	lemma = nm->mkNode(ITE, t, lemma, t[0].eqNode(t[1]).notNode());
120		}
121	30558	return lemma;
122		}
123
124	11263	Node TermRegistry::lengthPositive(Node t)
125		{
126	11263	NodeManager* nm = NodeManager::currentNM();
127	22526	Node zero = nm->mkConst(Rational(0));
128	22526	Node emp = Word::mkEmptyWord(t.getType());
129	22526	Node tlen = nm->mkNode(STRING_LENGTH, t);
130	22526	Node tlenEqZero = tlen.eqNode(zero);
131	22526	Node tEqEmp = t.eqNode(emp);
132	22526	Node caseEmpty = nm->mkNode(AND, tlenEqZero, tEqEmp);
133	22526	Node caseNEmpty = nm->mkNode(GT, tlen, zero);
134		// (or (and (= (str.len t) 0) (= t "")) (> (str.len t) 0))
135	22526	return nm->mkNode(OR, caseEmpty, caseNEmpty);
136		}
137
138	158451	void TermRegistry::preRegisterTerm(TNode n)
139		{
140	158451	if (d_preregisteredTerms.find(n) != d_preregisteredTerms.end())
141		{
142	65046	return;
143		}
144	157519	eq::EqualityEngine* ee = d_state.getEqualityEngine();
145	157519	d_preregisteredTerms.insert(n);
146	315038	Trace("strings-preregister")
147	157519	<< "TheoryString::preregister : " << n << std::endl;
148		// check for logic exceptions
149	157519	Kind k = n.getKind();
150	157519	if (!options::stringExp())
151		{
152	4103	if (k == STRING_INDEXOF \|\| k == STRING_INDEXOF_RE \|\| k == STRING_ITOS
153	4103	\|\| k == STRING_STOI \|\| k == STRING_REPLACE \|\| k == STRING_SUBSTR
154	4103	\|\| k == STRING_REPLACE_ALL \|\| k == SEQ_NTH \|\| k == STRING_REPLACE_RE
155	4103	\|\| k == STRING_REPLACE_RE_ALL \|\| k == STRING_CONTAINS \|\| k == STRING_LEQ
156	4103	\|\| k == STRING_TOLOWER \|\| k == STRING_TOUPPER \|\| k == STRING_REV
157	4103	\|\| k == STRING_UPDATE)
158		{
159		std::stringstream ss;
160		ss << "Term of kind " << k
161		<< " not supported in default mode, try --strings-exp";
162		throw LogicException(ss.str());
163		}
164		}
165	157519	if (k == EQUAL)
166		{
167	60017	if (n[0].getType().isRegExp())
168		{
169		std::stringstream ss;
170		ss << "Equality between regular expressions is not supported";
171		throw LogicException(ss.str());
172		}
173	60017	ee->addTriggerPredicate(n);
174	60017	return;
175		}
176	97502	else if (k == STRING_IN_REGEXP)
177		{
178	3165	d_im->requirePhase(n, true);
179	3165	ee->addTriggerPredicate(n);
180	3165	ee->addTerm(n[0]);
181	3165	ee->addTerm(n[1]);
182	3165	return;
183		}
184	94337	else if (k == STRING_TO_CODE)
185		{
186	2953	d_hasStrCode = true;
187		}
188	91384	else if (k == REGEXP_RANGE)
189		{
190	255	for (const Node& nc : n)
191		{
192	170	if (!nc.isConst())
193		{
194		throw LogicException(
195		"expecting a constant string term in regexp range");
196		}
197	170	if (nc.getConst<String>().size() != 1)
198		{
199		throw LogicException(
200		"expecting a single constant string term in regexp range");
201		}
202		}
203		}
204	94337	registerTerm(n, 0);
205	188674	TypeNode tn = n.getType();
206	94337	if (tn.isRegExp() && n.isVar())
207		{
208		std::stringstream ss;
209		ss << "Regular expression variables are not supported.";
210		throw LogicException(ss.str());
211		}
212	94337	if (tn.isString()) // string-only
213		{
214		// all characters of constants should fall in the alphabet
215	47818	if (n.isConst())
216		{
217	8158	std::vector<unsigned> vec = n.getConst<String>().getVec();
218	17746	for (unsigned u : vec)
219		{
220	13667	if (u >= d_cardSize)
221		{
222		std::stringstream ss;
223		ss << "Characters in string \"" << n
224		<< "\" are outside of the given alphabet.";
225		throw LogicException(ss.str());
226		}
227		}
228		}
229	47818	ee->addTerm(n);
230		}
231	46519	else if (tn.isBoolean())
232		{
233		// All kinds that we do congruence over that may return a Boolean go here
234	1883	if (k == STRING_CONTAINS \|\| k == STRING_LEQ \|\| k == SEQ_NTH)
235		{
236		// Get triggered for both equal and dis-equal
237	1877	ee->addTriggerPredicate(n);
238		}
239		}
240		else
241		{
242		// Function applications/predicates
243	44636	ee->addTerm(n);
244		}
245		// Set d_functionsTerms stores all function applications that are
246		// relevant to theory combination. Notice that this is a subset of
247		// the applications whose kinds are function kinds in the equality
248		// engine. This means it does not include applications of operators
249		// like re.++, which is not a function kind in the equality engine.
250		// Concatenation terms do not need to be considered here because
251		// their arguments have string type and do not introduce any shared
252		// terms.
253	246808	if (n.hasOperator() && ee->isFunctionKind(k)
254	148869	&& kindToTheoryId(k) == THEORY_STRINGS && k != STRING_CONCAT)
255		{
256	43606	d_functionsTerms.push_back(n);
257		}
258	94337	if (options::stringFMF())
259		{
260	15158	if (tn.isStringLike())
261		{
262		// Our decision strategy will minimize the length of this term if it is a
263		// variable but not an internally generated Skolem, or a term that does
264		// not belong to this theory.
265	11096	if (n.isVar() ? !d_skCache.isSkolem(n)
266	3230	: kindToTheoryId(k) != THEORY_STRINGS)
267		{
268	518	d_inputVars.insert(n);
269	518	Trace("strings-preregister") << "input variable: " << n << std::endl;
270		}
271		}
272		}
273		}
274
275	206767	void TermRegistry::registerTerm(Node n, int effort)
276		{
277	413534	Trace("strings-register") << "TheoryStrings::registerTerm() " << n
278	206767	<< ", effort = " << effort << std::endl;
279	206767	if (d_registeredTerms.find(n) != d_registeredTerms.end())
280		{
281	149560	Trace("strings-register") << "...already registered" << std::endl;
282	299120	return;
283		}
284	57207	bool do_register = true;
285	114414	TypeNode tn = n.getType();
286	57207	if (!tn.isStringLike())
287		{
288	27437	if (options::stringEagerLen())
289		{
290	27437	do_register = effort == 0;
291		}
292		else
293		{
294		do_register = effort > 0 \|\| n.getKind() != STRING_CONCAT;
295		}
296		}
297	57207	if (!do_register)
298		{
299		Trace("strings-register") << "...do not register" << std::endl;
300		return;
301		}
302	57207	Trace("strings-register") << "...register" << std::endl;
303	57207	d_registeredTerms.insert(n);
304		// ensure the type is registered
305	57207	registerType(tn);
306	114414	TrustNode regTermLem;
307	57207	if (tn.isStringLike())
308		{
309		// register length information:
310		// for variables, split on empty vs positive length
311		// for concat/const/replace, introduce proxy var and state length relation
312	29770	regTermLem = getRegisterTermLemma(n);
313		}
314	27437	else if (n.getKind() != STRING_CONTAINS)
315		{
316		// we don't send out eager reduction lemma for str.contains currently
317	52742	Node eagerRedLemma = eagerReduce(n, &d_skCache);
318	26371	if (!eagerRedLemma.isNull())
319		{
320		// if there was an eager reduction, we make the trust node for it
321	2013	if (d_epg != nullptr)
322		{
323	624	regTermLem = d_epg->mkTrustNode(
324	312	eagerRedLemma, PfRule::STRING_EAGER_REDUCTION, {}, {n});
325		}
326		else
327		{
328	1701	regTermLem = TrustNode::mkTrustLemma(eagerRedLemma, nullptr);
329		}
330		}
331		}
332	57207	if (!regTermLem.isNull())
333		{
334	22894	Trace("strings-lemma") << "Strings::Lemma REG-TERM : " << regTermLem
335	11447	<< std::endl;
336	22894	Trace("strings-assert")
337	11447	<< "(assert " << regTermLem.getNode() << ")" << std::endl;
338	11447	d_im->trustedLemma(regTermLem, InferenceId::STRINGS_REGISTER_TERM);
339		}
340		}
341
342	57207	void TermRegistry::registerType(TypeNode tn)
343		{
344	57207	if (d_registeredTypes.find(tn) != d_registeredTypes.end())
345		{
346	54855	return;
347		}
348	2352	d_registeredTypes.insert(tn);
349	2352	if (tn.isStringLike())
350		{
351		// preregister the empty word for the type
352	1864	Node emp = Word::mkEmptyWord(tn);
353	932	if (!d_state.hasTerm(emp))
354		{
355	932	preRegisterTerm(emp);
356		}
357		}
358		}
359
360	29770	TrustNode TermRegistry::getRegisterTermLemma(Node n)
361		{
362	29770	Assert(n.getType().isStringLike());
363	29770	NodeManager* nm = NodeManager::currentNM();
364		// register length information:
365		// for variables, split on empty vs positive length
366		// for concat/const/replace, introduce proxy var and state length relation
367	59540	Node lsum;
368	29770	if (n.getKind() != STRING_CONCAT && !n.isConst())
369		{
370	20648	Node lsumb = nm->mkNode(STRING_LENGTH, n);
371	20492	lsum = Rewriter::rewrite(lsumb);
372		// can register length term if it does not rewrite
373	20492	if (lsum == lsumb)
374		{
375	20336	registerTermAtomic(n, LENGTH_SPLIT);
376	20336	return TrustNode::null();
377		}
378		}
379	18868	Node sk = d_skCache.mkSkolemCached(n, SkolemCache::SK_PURIFY, "lsym");
380		StringsProxyVarAttribute spva;
381	9434	sk.setAttribute(spva, true);
382	18868	Node eq = Rewriter::rewrite(sk.eqNode(n));
383	9434	d_proxyVar[n] = sk;
384		// If we are introducing a proxy for a constant or concat term, we do not
385		// need to send lemmas about its length, since its length is already
386		// implied.
387	9434	if (n.isConst() \|\| n.getKind() == STRING_CONCAT)
388		{
389		// do not send length lemma for sk.
390	9278	registerTermAtomic(sk, LENGTH_IGNORE);
391		}
392	18868	Node skl = nm->mkNode(STRING_LENGTH, sk);
393	9434	if (n.getKind() == STRING_CONCAT)
394		{
395	11720	std::vector<Node> nodeVec;
396	19952	for (const Node& nc : n)
397		{
398	14092	if (nc.getAttribute(StringsProxyVarAttribute()))
399		{
400	60	Assert(d_proxyVarToLength.find(nc) != d_proxyVarToLength.end());
401	60	nodeVec.push_back(d_proxyVarToLength[nc]);
402		}
403		else
404		{
405	28064	Node lni = nm->mkNode(STRING_LENGTH, nc);
406	14032	nodeVec.push_back(lni);
407		}
408		}
409	5860	lsum = nm->mkNode(PLUS, nodeVec);
410	5860	lsum = Rewriter::rewrite(lsum);
411		}
412	3574	else if (n.isConst())
413		{
414	3418	lsum = nm->mkConst(Rational(Word::getLength(n)));
415		}
416	9434	Assert(!lsum.isNull());
417	9434	d_proxyVarToLength[sk] = lsum;
418	18868	Node ceq = Rewriter::rewrite(skl.eqNode(lsum));
419
420	18868	Node ret = nm->mkNode(AND, eq, ceq);
421
422		// it is a simple rewrite to justify this
423	9434	if (d_epg != nullptr)
424		{
425	1280	return d_epg->mkTrustNode(ret, PfRule::MACRO_SR_PRED_INTRO, {}, {ret});
426		}
427	8154	return TrustNode::mkTrustLemma(ret, nullptr);
428		}
429
430	31037	void TermRegistry::registerTermAtomic(Node n, LengthStatus s)
431		{
432	31037	if (d_lengthLemmaTermsCache.find(n) != d_lengthLemmaTermsCache.end())
433		{
434	30656	return;
435		}
436	20340	d_lengthLemmaTermsCache.insert(n);
437
438	20340	if (s == LENGTH_IGNORE)
439		{
440		// ignore it
441	9262	return;
442		}
443	22156	std::map<Node, bool> reqPhase;
444	22156	TrustNode lenLem = getRegisterTermAtomicLemma(n, s, reqPhase);
445	11078	if (!lenLem.isNull())
446		{
447	22148	Trace("strings-lemma") << "Strings::Lemma REGISTER-TERM-ATOMIC : " << lenLem
448	11074	<< std::endl;
449	22148	Trace("strings-assert")
450	11074	<< "(assert " << lenLem.getNode() << ")" << std::endl;
451	11074	d_im->trustedLemma(lenLem, InferenceId::STRINGS_REGISTER_TERM_ATOMIC);
452		}
453	33194	for (const std::pair<const Node, bool>& rp : reqPhase)
454		{
455	22116	d_im->requirePhase(rp.first, rp.second);
456		}
457		}
458
459	35386	SkolemCache* TermRegistry::getSkolemCache() { return &d_skCache; }
460
461	6957	const context::CDList<TNode>& TermRegistry::getFunctionTerms() const
462		{
463	6957	return d_functionsTerms;
464		}
465
466	78	const context::CDHashSet<Node>& TermRegistry::getInputVars() const
467		{
468	78	return d_inputVars;
469		}
470
471	11894	bool TermRegistry::hasStringCode() const { return d_hasStrCode; }
472
473	11078	TrustNode TermRegistry::getRegisterTermAtomicLemma(
474		Node n, LengthStatus s, std::map<Node, bool>& reqPhase)
475		{
476	11078	if (n.isConst())
477		{
478		// No need to send length for constant terms. This case may be triggered
479		// for cases where the skolem cache automatically replaces a skolem by
480		// a constant.
481	4	return TrustNode::null();
482		}
483	11074	Assert(n.getType().isStringLike());
484	11074	NodeManager* nm = NodeManager::currentNM();
485	22148	Node n_len = nm->mkNode(kind::STRING_LENGTH, n);
486	22148	Node emp = Word::mkEmptyWord(n.getType());
487	11074	if (s == LENGTH_GEQ_ONE)
488		{
489	32	Node neq_empty = n.eqNode(emp).negate();
490	32	Node len_n_gt_z = nm->mkNode(GT, n_len, d_zero);
491	32	Node len_geq_one = nm->mkNode(AND, neq_empty, len_n_gt_z);
492	32	Trace("strings-lemma") << "Strings::Lemma SK-GEQ-ONE : " << len_geq_one
493	16	<< std::endl;
494	16	Trace("strings-assert") << "(assert " << len_geq_one << ")" << std::endl;
495	16	return TrustNode::mkTrustLemma(len_geq_one, nullptr);
496		}
497
498	11058	if (s == LENGTH_ONE)
499		{
500		Node len_one = n_len.eqNode(d_one);
501		Trace("strings-lemma") << "Strings::Lemma SK-ONE : " << len_one
502		<< std::endl;
503		Trace("strings-assert") << "(assert " << len_one << ")" << std::endl;
504		return TrustNode::mkTrustLemma(len_one, nullptr);
505		}
506	11058	Assert(s == LENGTH_SPLIT);
507
508		// get the positive length lemma
509	22116	Node lenLemma = lengthPositive(n);
510		// split whether the string is empty
511	22116	Node n_len_eq_z = n_len.eqNode(d_zero);
512	22116	Node n_len_eq_z_2 = n.eqNode(emp);
513	22116	Node case_empty = nm->mkNode(AND, n_len_eq_z, n_len_eq_z_2);
514	22116	Node case_emptyr = Rewriter::rewrite(case_empty);
515	11058	if (!case_emptyr.isConst())
516		{
517		// prefer trying the empty case first
518		// notice that requirePhase must only be called on rewritten literals that
519		// occur in the CNF stream.
520	11058	n_len_eq_z = Rewriter::rewrite(n_len_eq_z);
521	11058	Assert(!n_len_eq_z.isConst());
522	11058	reqPhase[n_len_eq_z] = true;
523	11058	n_len_eq_z_2 = Rewriter::rewrite(n_len_eq_z_2);
524	11058	Assert(!n_len_eq_z_2.isConst());
525	11058	reqPhase[n_len_eq_z_2] = true;
526		}
527		else
528		{
529		// If n = "" ---> true or len( n ) = 0 ----> true, then we expect that
530		// n ---> "". Since this method is only called on non-constants n, it must
531		// be that n = "" ^ len( n ) = 0 does not rewrite to true.
532		Assert(!case_emptyr.getConst<bool>());
533		}
534
535	11058	if (d_epg != nullptr)
536		{
537	1470	return d_epg->mkTrustNode(lenLemma, PfRule::STRING_LENGTH_POS, {}, {n});
538		}
539	9588	return TrustNode::mkTrustLemma(lenLemma, nullptr);
540		}
541
542	411757	Node TermRegistry::getSymbolicDefinition(Node n, std::vector<Node>& exp) const
543		{
544	411757	if (n.getNumChildren() == 0)
545		{
546	366772	Node pn = getProxyVariableFor(n);
547	183386	if (pn.isNull())
548		{
549	20057	return Node::null();
550		}
551	326658	Node eq = n.eqNode(pn);
552	163329	eq = Rewriter::rewrite(eq);
553	163329	if (std::find(exp.begin(), exp.end(), eq) == exp.end())
554		{
555	159993	exp.push_back(eq);
556		}
557	163329	return pn;
558		}
559	456742	std::vector<Node> children;
560	228371	if (n.getMetaKind() == metakind::PARAMETERIZED)
561		{
562	42	children.push_back(n.getOperator());
563		}
564	604949	for (const Node& nc : n)
565		{
566	404483	if (n.getType().isRegExp())
567		{
568	142814	children.push_back(nc);
569		}
570		else
571		{
572	495433	Node ns = getSymbolicDefinition(nc, exp);
573	261669	if (ns.isNull())
574		{
575	27905	return Node::null();
576		}
577		else
578		{
579	233764	children.push_back(ns);
580		}
581		}
582		}
583	200466	return NodeManager::currentNM()->mkNode(n.getKind(), children);
584		}
585
586	191264	Node TermRegistry::getProxyVariableFor(Node n) const
587		{
588	191264	NodeNodeMap::const_iterator it = d_proxyVar.find(n);
589	191264	if (it != d_proxyVar.end())
590		{
591	170897	return (*it).second;
592		}
593	20367	return Node::null();
594		}
595
596	7552	Node TermRegistry::ensureProxyVariableFor(Node n)
597		{
598	7552	Node proxy = getProxyVariableFor(n);
599	7552	if (proxy.isNull())
600		{
601	294	registerTerm(n, 0);
602	294	proxy = getProxyVariableFor(n);
603		}
604	7552	Assert(!proxy.isNull());
605	7552	return proxy;
606		}
607
608	89982	void TermRegistry::removeProxyEqs(Node n, std::vector<Node>& unproc) const
609		{
610	89982	if (n.getKind() == AND)
611		{
612	2821	for (const Node& nc : n)
613		{
614	2232	removeProxyEqs(nc, unproc);
615		}
616	1194	return;
617		}
618	89393	Trace("strings-subs-proxy") << "Input : " << n << std::endl;
619	178770	Node ns = Rewriter::rewrite(n);
620	89393	if (ns.getKind() == EQUAL)
621		{
622	267455	for (size_t i = 0; i < 2; i++)
623		{
624		// determine whether this side has a proxy variable
625	178314	if (ns[i].getAttribute(StringsProxyVarAttribute()))
626		{
627	32	if (getProxyVariableFor(ns[1 - i]) == ns[i])
628		{
629	32	Trace("strings-subs-proxy")
630	16	<< "...trivial definition via " << ns[i] << std::endl;
631		// it is a trivial equality, e.g. between a proxy variable
632		// and its definition
633	16	return;
634		}
635		}
636		}
637		}
638	89377	if (!n.isConst() \|\| !n.getConst<bool>())
639		{
640	89367	Trace("strings-subs-proxy") << "...unprocessed" << std::endl;
641	89367	unproc.push_back(n);
642		}
643		}
644
645		} // namespace strings
646		} // namespace theory
647	29577	} // namespace cvc5