Add ProofNode data structure (#4311)

This is the core data structure for proofs in the new proofs infrastructure. PfRule is a global enumeration of ids of proof nodes (analogous to Kind for Nodes).

1 files changed, 78 insertions, 0 deletions

diff --git a/src/expr/proof_rule.h b/src/expr/proof_rule.h
new file mode 100644
index 000000000..16f4ca971
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+++ b/src/expr/proof_rule.h
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+/*********************                                                        */
+/*! \file proof_rule.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 rule enumeration
+ **/
+
+#include "cvc4_private.h"
+
+#ifndef CVC4__EXPR__PROOF_RULE_H
+#define CVC4__EXPR__PROOF_RULE_H
+
+#include <iosfwd>
+
+namespace CVC4 {
+
+/**
+ * An enumeration for proof rules. This enumeration is analogous to Kind for
+ * Node objects. In the documentation below, P:F denotes a ProofNode that
+ * proves formula F.
+ *
+ * Conceptually, the following proof rules form a calculus whose target
+ * user is the Node-level theory solvers. This means that the rules below
+ * are designed to reason about, among other things, common operations on Node
+ * objects like Rewriter::rewrite or Node::substitute. It is intended to be
+ * translated or printed in other formats.
+ *
+ * The following PfRule values include core rules and those categorized by
+ * theory, including the theory of equality.
+ *
+ * The "core rules" include ASSUME, which represents an open leaf in a proof.
+ * The core rules additionally correspond to generic operations that are done
+ * internally on nodes, e.g. calling Rewriter::rewrite.
+ */
+enum class PfRule : uint32_t
+{
+  //================================================= Core rules
+  // ======== Assumption (a leaf)
+  // Children: none
+  // Arguments: (F)
+  // --------------
+  // Conclusion F
+  ASSUME,
+
+  //================================================= Unknown rule
+  UNKNOWN,
+};
+
+/**
+ * Converts a proof rule to a string. Note: This function is also used in
+ * `safe_print()`. Changing this function name or signature will result in
+ * `safe_print()` printing "<unsupported>" instead of the proper strings for
+ * the enum values.
+ *
+ * @param id The proof rule
+ * @return The name of the proof rule
+ */
+const char* toString(PfRule id);
+
+/**
+ * Writes a proof rule name to a stream.
+ *
+ * @param out The stream to write to
+ * @param id The proof rule to write to the stream
+ * @return The stream
+ */
+std::ostream& operator<<(std::ostream& out, PfRule id);
+
+}  // namespace CVC4
+
+#endif /* CVC4__EXPR__PROOF_RULE_H */