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/******************************************************************************
* Top contributors (to current version):
* Andrew Reynolds, Aina Niemetz
*
* 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 quantifiers proof checker.
*/
#include "theory/quantifiers/proof_checker.h"
#include "expr/node_algorithm.h"
#include "expr/skolem_manager.h"
#include "theory/builtin/proof_checker.h"
using namespace cvc5::kind;
namespace cvc5 {
namespace theory {
namespace quantifiers {
void QuantifiersProofRuleChecker::registerTo(ProofChecker* pc)
{
// add checkers
pc->registerChecker(PfRule::SKOLEM_INTRO, this);
pc->registerChecker(PfRule::EXISTS_INTRO, this);
pc->registerChecker(PfRule::SKOLEMIZE, this);
pc->registerChecker(PfRule::INSTANTIATE, this);
// trusted rules
pc->registerTrustedChecker(PfRule::QUANTIFIERS_PREPROCESS, this, 3);
}
Node QuantifiersProofRuleChecker::checkInternal(
PfRule id, const std::vector<Node>& children, const std::vector<Node>& args)
{
NodeManager* nm = NodeManager::currentNM();
SkolemManager* sm = nm->getSkolemManager();
// compute what was proven
if (id == PfRule::EXISTS_INTRO)
{
Assert(children.size() == 1);
Assert(args.size() == 1);
Node p = children[0];
Node exists = args[0];
if (exists.getKind() != kind::EXISTS || exists[0].getNumChildren() != 1)
{
return Node::null();
}
std::unordered_map<Node, Node> subs;
if (!expr::match(exists[1], p, subs))
{
return Node::null();
}
// substitution must contain only the variable of the existential
for (const std::pair<const Node, Node>& s : subs)
{
if (s.first != exists[0][0])
{
return Node::null();
}
}
return exists;
}
else if (id == PfRule::SKOLEM_INTRO)
{
Assert(children.empty());
Assert(args.size() == 1);
Node t = SkolemManager::getOriginalForm(args[0]);
return args[0].eqNode(t);
}
else if (id == PfRule::SKOLEMIZE)
{
Assert(children.size() == 1);
Assert(args.empty());
// can use either negated FORALL or EXISTS
if (children[0].getKind() != EXISTS
&& (children[0].getKind() != NOT || children[0][0].getKind() != FORALL))
{
return Node::null();
}
Node exists;
if (children[0].getKind() == EXISTS)
{
exists = children[0];
}
else
{
std::vector<Node> echildren(children[0][0].begin(), children[0][0].end());
echildren[1] = echildren[1].notNode();
exists = nm->mkNode(EXISTS, echildren);
}
std::vector<Node> skolems;
Node res = sm->mkSkolemize(exists, skolems, "k");
return res;
}
else if (id == PfRule::INSTANTIATE)
{
Assert(children.size() == 1);
if (children[0].getKind() != FORALL
|| args.size() != children[0][0].getNumChildren())
{
return Node::null();
}
Node body = children[0][1];
std::vector<Node> vars;
std::vector<Node> subs;
for (unsigned i = 0, nargs = args.size(); i < nargs; i++)
{
vars.push_back(children[0][0][i]);
subs.push_back(args[i]);
}
Node inst =
body.substitute(vars.begin(), vars.end(), subs.begin(), subs.end());
return inst;
}
else if (id == PfRule::QUANTIFIERS_PREPROCESS)
{
Assert(!args.empty());
Assert(args[0].getType().isBoolean());
return args[0];
}
// no rule
return Node::null();
}
} // namespace quantifiers
} // namespace theory
} // namespace cvc5
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