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+/*********************                                                        */
+/*! \file proof_step_buffer.h
+ ** \verbatim
+ ** Top contributors (to current version):
+ **   Andrew Reynolds
+ ** 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 Proof step and proof step buffer utilities.
+ **/
+
+#include "cvc4_private.h"
+
+#ifndef CVC4__EXPR__PROOF_STEP_BUFFER_H
+#define CVC4__EXPR__PROOF_STEP_BUFFER_H
+
+#include <vector>
+
+#include "expr/node.h"
+#include "expr/proof_checker.h"
+#include "expr/proof_rule.h"
+
+namespace CVC4 {
+
+/**
+ * Information for constructing a step in a CDProof. Notice that the conclusion
+ * of the proof step is intentionally not included in this data structure.
+ * Instead, it is intended that conclusions may be associated with proof steps
+ * based on e.g. the result of proof checking.
+ */
+class ProofStep
+{
+ public:
+  ProofStep();
+  ProofStep(PfRule r,
+            const std::vector<Node>& children,
+            const std::vector<Node>& args);
+  /** The proof rule */
+  PfRule d_rule;
+  /** The proof children */
+  std::vector<Node> d_children;
+  /** The proof arguments */
+  std::vector<Node> d_args;
+};
+std::ostream& operator<<(std::ostream& out, ProofStep step);
+
+/**
+ * Class used to speculatively try and buffer a set of proof steps before
+ * sending them to a proof object.
+ */
+class ProofStepBuffer
+{
+ public:
+  ProofStepBuffer(ProofChecker* pc = nullptr);
+  ~ProofStepBuffer() {}
+  /**
+   * Returns the conclusion of the proof step, as determined by the proof
+   * checker of the given proof. If this is non-null, then the given step
+   * is added to the buffer maintained by this class.
+   *
+   * If expected is non-null, then this method returns null if the result of
+   * checking is not equal to expected.
+   */
+  Node tryStep(PfRule id,
+               const std::vector<Node>& children,
+               const std::vector<Node>& args,
+               Node expected = Node::null());
+  /** Same as above, without checking */
+  void addStep(PfRule id,
+               const std::vector<Node>& children,
+               const std::vector<Node>& args,
+               Node expected);
+  /** Multi-step version */
+  void addSteps(ProofStepBuffer& psb);
+  /** pop step */
+  void popStep();
+  /** Get num steps */
+  size_t getNumSteps() const;
+  /** Get steps */
+  const std::vector<std::pair<Node, ProofStep>>& getSteps() const;
+  /** Clear */
+  void clear();
+
+ private:
+  /** The proof checker*/
+  ProofChecker* d_checker;
+  /** the queued proof steps */
+  std::vector<std::pair<Node, ProofStep>> d_steps;
+};
+
+}  // namespace CVC4
+
+#endif /* CVC4__EXPR__PROOF_STEP_BUFFER_H */