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/********************* */
/*! \file alpha_equivalence.cpp
** \verbatim
** Top contributors (to current version):
** Andrew Reynolds
** This file is part of the CVC4 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.\endverbatim
**
** \brief Alpha equivalence checking
**
**/
#include "theory/quantifiers/alpha_equivalence.h"
#include "theory/quantifiers_engine.h"
using namespace CVC4::kind;
namespace CVC4 {
namespace theory {
namespace quantifiers {
struct sortTypeOrder {
expr::TermCanonize* d_tu;
bool operator() (TypeNode i, TypeNode j) {
return d_tu->getIdForType( i )<d_tu->getIdForType( j );
}
};
Node AlphaEquivalenceTypeNode::registerNode(
Node q,
Node t,
std::vector<TypeNode>& typs,
std::map<TypeNode, size_t>& typCount)
{
AlphaEquivalenceTypeNode* aetn = this;
size_t index = 0;
while (index < typs.size())
{
TypeNode curr = typs[index];
Assert(typCount.find(curr) != typCount.end());
Trace("aeq-debug") << "[" << curr << " " << typCount[curr] << "] ";
std::pair<TypeNode, size_t> key(curr, typCount[curr]);
aetn = &(aetn->d_children[key]);
index = index + 1;
}
Trace("aeq-debug") << " : ";
std::map<Node, Node>::iterator it = aetn->d_quant.find(t);
if (it != aetn->d_quant.end())
{
return it->second;
}
aetn->d_quant[t] = q;
return q;
}
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, size_t> typCount;
std::vector< TypeNode > typs;
for( unsigned i=0; i<q[0].getNumChildren(); i++ ){
TypeNode tn = q[0][i].getType();
typCount[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, typCount);
Trace("aeq") << " ...result : " << ret << std::endl;
return ret;
}
AlphaEquivalence::AlphaEquivalence(QuantifiersEngine* qe)
: d_termCanon(), d_aedb(&d_termCanon)
{
}
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)
{
// lemma ( q <=> d_quant )
// Notice that we infer this equivalence regardless of whether q or ret
// have annotations (e.g. user patterns, names, etc.).
Trace("alpha-eq") << "Alpha equivalent : " << std::endl;
Trace("alpha-eq") << " " << q << std::endl;
Trace("alpha-eq") << " " << ret << std::endl;
lem = q.eqNode(ret);
if (q.getNumChildren() == 3)
{
Notice() << "Ignoring annotated quantified formula based on alpha "
"equivalence: "
<< q << std::endl;
}
}
return lem;
}
} // namespace quantifiers
} // namespace theory
} // namespace CVC4
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