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+/*********************                                                        */
+/*! \file unconstrained_simplifier.h
+ ** \verbatim
+ ** Top contributors (to current version):
+ **   Clark Barrett, Tim King
+ ** This file is part of the CVC4 project.
+ ** Copyright (c) 2009-2018 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 Simplifications based on unconstrained variables
+ **
+ ** This module implements a preprocessing phase which replaces certain
+ ** "unconstrained" expressions by variables.  Based on Roberto
+ ** Bruttomesso's PhD thesis.
+ **/
+
+#include "cvc4_private.h"
+
+#ifndef __CVC4__PREPROCESSING_PASSES_UNCONSTRAINED_SIMPLIFIER_H
+#define __CVC4__PREPROCESSING_PASSES_UNCONSTRAINED_SIMPLIFIER_H
+
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+#include "context/context.h"
+#include "expr/node.h"
+#include "preprocessing/preprocessing_pass.h"
+#include "preprocessing/preprocessing_pass_context.h"
+#include "theory/logic_info.h"
+#include "theory/substitutions.h"
+#include "util/statistics_registry.h"
+
+namespace CVC4 {
+namespace preprocessing {
+namespace passes {
+
+class UnconstrainedSimplifier : public PreprocessingPass
+{
+ public:
+  UnconstrainedSimplifier(PreprocessingPassContext* preprocContext);
+  ~UnconstrainedSimplifier() override;
+
+  PreprocessingPassResult applyInternal(
+      AssertionPipeline* assertionsToPreprocess) override;
+
+ private:
+  /** number of expressions eliminated due to unconstrained simplification */
+  IntStat d_numUnconstrainedElim;
+
+  using TNodeCountMap = std::unordered_map<TNode, unsigned, TNodeHashFunction>;
+  using TNodeMap = std::unordered_map<TNode, TNode, TNodeHashFunction>;
+  using TNodeSet = std::unordered_set<TNode, TNodeHashFunction>;
+
+  TNodeCountMap d_visited;
+  TNodeMap d_visitedOnce;
+  TNodeSet d_unconstrained;
+
+  context::Context* d_context;
+  theory::SubstitutionMap d_substitutions;
+
+  const LogicInfo& d_logicInfo;
+
+  void visitAll(TNode assertion);
+  Node newUnconstrainedVar(TypeNode t, TNode var);
+  void processUnconstrained();
+};
+
+}  // namespace passes
+}  // namespace preprocessing
+}  // namespace CVC4
+
+#endif