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/********************* -*- C++ -*- */
/** cnf_converter.cpp
** Original author: mdeters
** Major contributors: dejan
** Minor contributors (to current version): none
** This file is part of the CVC4 prototype.
** Copyright (c) 2009 The Analysis of Computer Systems Group (ACSys)
** Courant Institute of Mathematical Sciences
** New York University
** See the file COPYING in the top-level source directory for licensing
** information.
**
** A CNF converter for CVC4.
**/
#include "smt/cnf_converter.h"
#include "expr/node_builder.h"
#include "expr/node.h"
#include "util/output.h"
#include "util/Assert.h"
namespace CVC4 {
namespace smt {
static void printAST(std::ostream& out, const Node& n, int indent = 0) {
for(int i = 0; i < indent; ++i) {
out << " ";
}
if(n.getKind() == VARIABLE) {
out << "(VARIABLE " << n.getId();
} else {
out << "(" << n.getKind();
if(n.getNumChildren() > 0) {
out << std::endl;
}
for(Node::iterator i = n.begin(); i != n.end(); ++i) {
printAST(out, *i, indent + 1);
}
if(n.getNumChildren() > 0) {
for(int i = 0; i < indent; ++i) {
out << " ";
}
}
}
out << ")" << std::endl;
}
Node CnfConverter::convert(const Node& e) {
Node n;
if(conversionMapped(e)) {
Debug("cnf") << "conversion for " << e << " with id " << e.getId() << " is cached!" << std::endl;
n = getConversionMap(e);
} else {
switch(d_conversion) {
case CNF_DIRECT_EXPONENTIAL:
n = directConvert(e);
break;
case CNF_VAR_INTRODUCTION:
n = varIntroductionConvert(e);
break;
default:
Unhandled(d_conversion);
}
Debug("cnf") << "mapping conversion " << e << " with id " << e.getId() << " to " << n << " with id " << n.getId() << std::endl;
mapConversion(e, n);
Assert(conversionMapped(e));
Assert(getConversionMap(e) == n);
}
Debug("cnf") << "CONVERTED ================" << std::endl;
printAST(Debug("cnf"), e);
Debug("cnf") << "TO ================" << std::endl;
printAST(Debug("cnf"), n);
Debug("cnf") << "==========================" << std::endl;
return n;
}
Node CnfConverter::compressNOT(const Node& e) {
Assert(e.getKind() == NOT);
// short-circuit trivial NOTs
if(e[0].getKind() == TRUE) {
return d_nm->mkNode(FALSE);
} else if(e[0].getKind() == FALSE) {
return d_nm->mkNode(TRUE);
} else if(e[0].getKind() == NOT) {
return convert(e[0][0]);
} else {
Node f = convert(e[0]);
// push NOTs inside of ANDs and ORs
if(f.getKind() == AND) {
NodeBuilder<> n(OR);
for(Node::iterator i = f.begin(); i != f.end(); ++i) {
if((*i).getKind() == NOT) {
n << (*i)[0];
} else {
n << d_nm->mkNode(NOT, *i);
}
}
return n;
}
if(f.getKind() == OR) {
NodeBuilder<> n(AND);
for(Node::iterator i = f.begin(); i != f.end(); ++i) {
if((*i).getKind() == NOT) {
n << (*i)[0];
} else {
n << d_nm->mkNode(NOT, *i);
}
}
return n;
}
return e;
}
}
Node CnfConverter::directConvert(const Node& e) {
if(e.getKind() == NOT) {
return compressNOT(e);
} else if(e.getKind() == AND) {
return flatten<AND>(e);
} else if(e.getKind() == OR) {
Node n = flatten<OR>(e);
NodeBuilder<> m(OR);
directOrHelper(n.begin(), n.end(), m);
return m;
}
return e;
}
void CnfConverter::directOrHelper(Node::iterator p, Node::iterator end, NodeBuilder<>& result) {
while(p != end) {
if((*p).getKind() == AND) {
Debug("cnf") << "orHelper: p " << *p << std::endl;
Debug("cnf") << " end " << std::endl;
Debug("cnf") << " result " << result << std::endl;
NodeBuilder<> resultPrefix = result;
result = NodeBuilder<>(AND);
for(Node::iterator i = (*p).begin(); i != (*p).end(); ++i) {
NodeBuilder<> r = resultPrefix;
// is this a double-convert since we did OR flattening before?
r << convert(*i);
Node::iterator p2 = p;
directOrHelper(++p2, end, r);
result << r;
}
} else {
Debug("cnf") << "orHelper: passing through a conversion of " << *p << std::endl;
// is this a double-convert since we did OR flattening before?
result << convert(*p);
}
Debug("cnf") << " ** result now " << result << std::endl;
++p;
}
}
Node CnfConverter::varIntroductionConvert(const Node& e) {
if(e.getKind() == NOT) {
return compressNOT(e);
} else if(e.getKind() == AND) {
return flatten<AND>(e);
} else if(e.getKind() == OR) {
Node n = flatten<OR>(e);
Debug("cnf") << "about to handle an OR:" << std::endl;
printAST(Debug("cnf"), n);
NodeBuilder<> m(AND);
NodeBuilder<> extras(OR);
varIntroductionOrHelper(n.begin(), n.end(), m, extras);
if(m.getNumChildren() > 0) {
return m << extras;
} else {
return extras;
}
}
return e;
}
void CnfConverter::varIntroductionOrHelper(Node::iterator p, Node::iterator end, NodeBuilder<>& result, NodeBuilder<>& extras) {
while(p != end) {
if((*p).getKind() == AND) {
Debug("cnf") << "orHelper: p " << *p << std::endl;
printAST(Debug("cnf"), *p);
Debug("cnf") << " end " << std::endl;
Debug("cnf") << " result " << result << std::endl;
Debug("cnf") << " extras " << extras << std::endl;
Node var = d_nm->mkVar();
extras << var;
Debug("cnf") << " introduced var " << var << "(" << var.getId() << ")" << std::endl;
Node notVar = d_nm->mkNode(NOT, var);
for(Node::iterator i = (*p).begin(); i != (*p).end(); ++i) {
// is this a double-convert since we did OR flattening before?
result << d_nm->mkNode(OR, notVar, convert(*i));
}
} else {
// is this a double-convert since we did OR flattening before?
Debug("cnf") << "orHelper: p " << *p << std::endl;
Debug("cnf") << " end " << std::endl;
Debug("cnf") << " result " << result << std::endl;
Debug("cnf") << " extras " << extras << std::endl;
Debug("cnf") << " passing through" << std::endl;
extras << convert(*p);
}
Debug("cnf") << " ** result now " << result << std::endl;
Debug("cnf") << " ** extras now " << extras << std::endl;
++p;
}
}
}/* CVC4::smt namespace */
}/* CVC4 namespace */
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