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/********************* */
/*! \file alpha_equivalence.cpp
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds, Morgan Deters
** This file is part of the CVC4 project.
** Copyright (c) 2009-2019 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 Alpha equivalence checking
**
**/
#include "theory/quantifiers/alpha_equivalence.h"
#include "theory/quantifiers/term_canonize.h"
using namespace CVC4;
using namespace std;
using namespace CVC4::theory;
using namespace CVC4::theory::quantifiers;
using namespace CVC4::kind;
struct sortTypeOrder {
TermCanonize* d_tu;
bool operator() (TypeNode i, TypeNode j) {
return d_tu->getIdForType( i )<d_tu->getIdForType( j );
}
};
Node AlphaEquivalenceNode::registerNode(Node q, Node t)
{
AlphaEquivalenceNode* aen = this;
std::vector<Node> tt;
std::vector<int> arg_index;
tt.push_back(t);
std::map< Node, bool > visited;
while( !tt.empty() ){
if( tt.size()==arg_index.size()+1 ){
Node t = tt.back();
Node op;
if( t.hasOperator() ){
if( visited.find( t )==visited.end() ){
visited[t] = true;
op = t.getOperator();
arg_index.push_back( 0 );
}else{
op = t;
arg_index.push_back( -1 );
}
}else{
op = t;
arg_index.push_back( 0 );
}
Trace("aeq-debug") << op << " ";
aen = &(aen->d_children[op][t.getNumChildren()]);
}else{
Node t = tt.back();
int i = arg_index.back();
if( i==-1 || i==(int)t.getNumChildren() ){
tt.pop_back();
arg_index.pop_back();
}else{
tt.push_back( t[i] );
arg_index[arg_index.size()-1]++;
}
}
}
Trace("aeq-debug") << std::endl;
if( aen->d_quant.isNull() ){
aen->d_quant = q;
}
return aen->d_quant;
}
Node AlphaEquivalenceTypeNode::registerNode(Node q,
Node t,
std::vector<TypeNode>& typs,
std::map<TypeNode, int>& typ_count)
{
AlphaEquivalenceTypeNode* aetn = this;
unsigned index = 0;
while (index < typs.size())
{
TypeNode curr = typs[index];
Assert( typ_count.find( curr )!=typ_count.end() );
Trace("aeq-debug") << "[" << curr << " " << typ_count[curr] << "] ";
aetn = &(aetn->d_children[curr][typ_count[curr]]);
index = index + 1;
}
Trace("aeq-debug") << " : ";
return aetn->d_data.registerNode(q, t);
}
Node AlphaEquivalenceDb::addTerm(Node q)
{
Assert( q.getKind()==FORALL );
Trace("aeq") << "Alpha equivalence : register " << q << std::endl;
//construct canonical quantified formula
Node t = d_tc->getCanonicalTerm(q[1], true);
Trace("aeq") << " canonical form: " << t << std::endl;
//compute variable type counts
std::map< TypeNode, int > typ_count;
std::vector< TypeNode > typs;
for( unsigned i=0; i<q[0].getNumChildren(); i++ ){
TypeNode tn = q[0][i].getType();
typ_count[tn]++;
if( std::find( typs.begin(), typs.end(), tn )==typs.end() ){
typs.push_back( tn );
}
}
sortTypeOrder sto;
sto.d_tu = d_tc;
std::sort( typs.begin(), typs.end(), sto );
Trace("aeq-debug") << " ";
Node ret = d_ae_typ_trie.registerNode(q, t, typs, typ_count);
Trace("aeq") << " ...result : " << ret << std::endl;
return ret;
}
AlphaEquivalence::AlphaEquivalence(QuantifiersEngine* qe)
: d_aedb(qe->getTermCanonize())
{
}
Node AlphaEquivalence::reduceQuantifier(Node q)
{
Assert(q.getKind() == FORALL);
Trace("aeq") << "Alpha equivalence : register " << q << std::endl;
Node ret = d_aedb.addTerm(q);
Node lem;
if (ret != q)
{
// do not reduce annotated quantified formulas based on alpha equivalence
if (q.getNumChildren() == 2)
{
// lemma ( q <=> d_quant )
Trace("alpha-eq") << "Alpha equivalent : " << std::endl;
Trace("alpha-eq") << " " << q << std::endl;
Trace("alpha-eq") << " " << ret << std::endl;
lem = q.eqNode(ret);
}
}
return lem;
}
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