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/********************* */
/*! \file simplify_boolean_node.cpp
** \verbatim
** Top contributors (to current version):
** Guy Katz, Liana Hadarean, Andrew Reynolds
** This file is part of the CVC4 project.
** Copyright (c) 2009-2020 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 Simplifying a boolean node, needed for constructing LFSC proofs.
**
**/
#include "cvc4_private.h"
#include "proof_manager.h"
namespace CVC4 {
inline static Node eqNode(TNode n1, TNode n2) {
return NodeManager::currentNM()->mkNode(kind::EQUAL, n1, n2);
}
Node simplifyBooleanNode(const Node &n) {
if (n.isNull())
return n;
// Only simplify boolean nodes
if (!n.getType().isBoolean())
return n;
// Sometimes we get sent intermediate nodes that we shouldn't simplify.
// If a node doesn't have a literal, it's clearly intermediate - ignore.
if (!ProofManager::hasLitName(n))
return n;
// If we already simplified the node, ignore.
if (ProofManager::currentPM()->haveRewriteFilter(n.negate()))
return n;
std::string litName = ProofManager::getLitName(n.negate());
Node falseNode = NodeManager::currentNM()->mkConst(false);
Node trueNode = NodeManager::currentNM()->mkConst(true);
Node simplified = n;
// (not (= false b)), (not (= true b)))
if ((n.getKind() == kind::NOT) && (n[0].getKind() == kind::EQUAL) &&
(n[0][0].getKind() == kind::BOOLEAN_TERM_VARIABLE || n[0][1].getKind() == kind::BOOLEAN_TERM_VARIABLE)) {
Node lhs = n[0][0];
Node rhs = n[0][1];
if (lhs == falseNode) {
Assert(rhs != falseNode);
Assert(rhs.getKind() == kind::BOOLEAN_TERM_VARIABLE);
// (not (= false b)) --> true = b
simplified = eqNode(trueNode, rhs);
std::string simplifiedLitName = ProofManager::getLitName(simplified.negate());
std::stringstream newLitName;
newLitName << "(pred_not_iff_f _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(simplifiedLitName, newLitName.str());
} else if (rhs == falseNode) {
Assert(lhs != falseNode);
Assert(lhs.getKind() == kind::BOOLEAN_TERM_VARIABLE);
// (not (= b false)) --> b = true
simplified = eqNode(lhs, trueNode);
std::string simplifiedLitName = ProofManager::getLitName(simplified.negate());
std::stringstream newLitName;
newLitName << "(pred_not_iff_f_2 _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(simplifiedLitName, newLitName.str());
} else if (lhs == trueNode) {
Assert(rhs != trueNode);
Assert(rhs.getKind() == kind::BOOLEAN_TERM_VARIABLE);
// (not (= true b)) --> b = false
simplified = eqNode(falseNode, rhs);
std::string simplifiedLitName = ProofManager::getLitName(simplified.negate());
std::stringstream newLitName;
newLitName << "(pred_not_iff_t _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(simplifiedLitName, newLitName.str());
} else if (rhs == trueNode) {
Assert(lhs != trueNode);
Assert(lhs.getKind() == kind::BOOLEAN_TERM_VARIABLE);
// (not (= b true)) --> b = false
simplified = eqNode(lhs, falseNode);
std::string simplifiedLitName = ProofManager::getLitName(simplified.negate());
std::stringstream newLitName;
newLitName << "(pred_not_iff_t_2 _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(simplifiedLitName, newLitName.str());
}
} else if ((n.getKind() == kind::EQUAL) &&
(n[0].getKind() == kind::BOOLEAN_TERM_VARIABLE || n[1].getKind() == kind::BOOLEAN_TERM_VARIABLE)) {
Node lhs = n[0];
Node rhs = n[1];
if (lhs == falseNode) {
Assert(rhs != falseNode);
Assert(rhs.getKind() == kind::BOOLEAN_TERM_VARIABLE);
// (= false b)
std::stringstream newLitName;
newLitName << "(pred_iff_f _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(litName, newLitName.str());
} else if (rhs == falseNode) {
Assert(lhs != falseNode);
Assert(lhs.getKind() == kind::BOOLEAN_TERM_VARIABLE);
// (= b false))
std::stringstream newLitName;
newLitName << "(pred_iff_f_2 _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(litName, newLitName.str());
} else if (lhs == trueNode) {
Assert(rhs != trueNode);
Assert(rhs.getKind() == kind::BOOLEAN_TERM_VARIABLE);
// (= true b)
std::stringstream newLitName;
newLitName << "(pred_iff_t _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(litName, newLitName.str());
} else if (rhs == trueNode) {
Assert(lhs != trueNode);
Assert(lhs.getKind() == kind::BOOLEAN_TERM_VARIABLE);
// (= b true)
std::stringstream newLitName;
newLitName << "(pred_iff_t_2 _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(litName, newLitName.str());
}
} else if ((n.getKind() == kind::NOT) && (n[0].getKind() == kind::BOOLEAN_TERM_VARIABLE)) {
// (not b) --> b = false
simplified = eqNode(n[0], falseNode);
std::string simplifiedLitName = ProofManager::getLitName(simplified.negate());
std::stringstream newLitName;
newLitName << "(pred_eq_f _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(simplifiedLitName, newLitName.str());
} else if (n.getKind() == kind::BOOLEAN_TERM_VARIABLE) {
// (b) --> b = true
simplified = eqNode(n, trueNode);
std::string simplifiedLitName = ProofManager::getLitName(simplified.negate());
std::stringstream newLitName;
newLitName << "(pred_eq_t _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(simplifiedLitName, newLitName.str());
} else if ((n.getKind() == kind::NOT) && (n[0].getKind() == kind::SELECT)) {
// not(a[x]) --> a[x] = false
simplified = eqNode(n[0], falseNode);
std::string simplifiedLitName = ProofManager::getLitName(simplified.negate());
std::stringstream newLitName;
newLitName << "(pred_eq_f _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(simplifiedLitName, newLitName.str());
} else if (n.getKind() == kind::SELECT) {
// a[x] --> a[x] = true
simplified = eqNode(n, trueNode);
std::string simplifiedLitName = ProofManager::getLitName(simplified.negate());
std::stringstream newLitName;
newLitName << "(pred_eq_t _ " << litName << ")";
ProofManager::currentPM()->addRewriteFilter(simplifiedLitName, newLitName.str());
}
if (simplified != n)
Debug("pf::simplify") << "simplifyBooleanNode: " << n << " --> " << simplified << std::endl;
return simplified;
}
}/* CVC4 namespace */
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