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diff --git a/src/proof/proof_node_to_sexpr.h b/src/proof/proof_node_to_sexpr.h
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+/******************************************************************************
+ * Top contributors (to current version):
+ *   Andrew Reynolds, Haniel Barbosa, Gereon Kremer
+ *
+ * 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.
+ * ****************************************************************************
+ *
+ * Conversion from ProofNode to s-expressions.
+ */
+
+#include "cvc5_private.h"
+
+#ifndef CVC5__PROOF__PROOF_NODE_TO_SEXPR_H
+#define CVC5__PROOF__PROOF_NODE_TO_SEXPR_H
+
+#include <map>
+
+#include "expr/node.h"
+#include "proof/proof_rule.h"
+
+namespace cvc5 {
+
+class ProofNode;
+
+/** A class to convert ProofNode objects to s-expressions */
+class ProofNodeToSExpr
+{
+ public:
+  ProofNodeToSExpr();
+  ~ProofNodeToSExpr() {}
+  /** Convert the given proof node to an s-expression
+   *
+   * This is useful for operations where it is useful to view a ProofNode as
+   * a Node. Printing is one such example, where a ProofNode can be printed
+   * as a dag after this conversion.
+   *
+   * The s-expression for a ProofNode has the form:
+   *   (SEXPR (VAR "<d_rule>") S1 ... Sn (VAR ":args") (SEXPR <d_args>))
+   * where S1, ..., Sn are the s-expressions for its <d_children>.
+   */
+  Node convertToSExpr(const ProofNode* pn);
+
+ private:
+  /** map proof rules to a variable */
+  std::map<PfRule, Node> d_pfrMap;
+  /** Dummy ":args" marker */
+  Node d_argsMarker;
+  /** Dummy ":conclusion" marker */
+  Node d_conclusionMarker;
+  /** map proof nodes to their s-expression */
+  std::map<const ProofNode*, Node> d_pnMap;
+  /**
+   * map nodes to a bound variable, used for nodes that have special AST status
+   * like builtin operators
+   */
+  std::map<Node, Node> d_nodeMap;
+  /** get or make pf rule variable */
+  Node getOrMkPfRuleVariable(PfRule r);
+  /** get or make node variable */
+  Node getOrMkNodeVariable(Node n);
+};
+
+}  // namespace cvc5
+
+#endif /* CVC5__PROOF__PROOF_RULE_H */