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/******************************************************************************
* Top contributors (to current version):
* Andrew Reynolds
*
* 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.
* ****************************************************************************
*
* Lambda lifting
*/
#include "cvc5_private.h"
#ifndef CVC5__THEORY__UF__LAMBDA_LIFT_H
#define CVC5__THEORY__UF__LAMBDA_LIFT_H
#include "context/cdhashmap.h"
#include "context/cdhashset.h"
#include "expr/node.h"
#include "proof/eager_proof_generator.h"
#include "proof/trust_node.h"
#include "smt/env_obj.h"
#include "theory/skolem_lemma.h"
namespace cvc5 {
namespace theory {
namespace uf {
/**
* Module for doing various operations on lambdas, including lambda lifting.
*
* In the following, we say a "lambda function" is a skolem variable that
* was introduced as a purification skolem for a lambda term.
*/
class LambdaLift : protected EnvObj
{
typedef context::CDHashSet<Node> NodeSet;
typedef context::CDHashMap<Node, Node> NodeNodeMap;
public:
LambdaLift(Env& env);
/**
* process, return the trust node corresponding to the lemma for the lambda
* lifting of (lambda) term node, or null if it is not a lambda or if
* the lambda lifting lemma has already been generated in this context.
*/
TrustNode lift(Node node);
/**
* This method has the same contract as Theory::ppRewrite.
* Preprocess, return the trust node corresponding to the rewrite. A null
* trust node indicates no rewrite.
*/
TrustNode ppRewrite(Node node, std::vector<SkolemLemma>& lems);
/** Get the lambda term for skolem, if skolem is a lambda function. */
Node getLambdaFor(TNode skolem) const;
/**
* Beta-reduce node. If node is APPLY_UF and its operator is a lambda
* function known by this class, then this method returns the beta
* reduced version of node. We only beta-reduce the top-most application
* in node.
*
* This method returns the trust node corresponding to the rewrite of node to
* the return value. It returns the null trust node if no beta reduction is
* possible for node.
*/
TrustNode betaReduce(TNode node) const;
/** Beta-reduce the given lambda on the given arguments. */
Node betaReduce(TNode lam, const std::vector<Node>& args) const;
private:
/**
* Get assertion for node, which is the axiom defining
*/
static Node getAssertionFor(TNode node);
/** Get skolem for lambda term node, returns its purification skolem */
static Node getSkolemFor(TNode node);
/** The nodes we have already returned trust nodes for */
NodeSet d_lifted;
/** Mapping skolems to their lambda */
NodeNodeMap d_lambdaMap;
/** An eager proof generator */
std::unique_ptr<EagerProofGenerator> d_epg;
};
} // namespace uf
} // namespace theory
} // namespace cvc5
#endif /* CVC5__THEORY__UF__LAMBDA_LIFT_H */
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