Add bags inference generator (#5731)

This PR adds inference generator for basic bag rules.

1 files changed, 128 insertions, 0 deletions

diff --git a/src/theory/bags/infer_info.h b/src/theory/bags/infer_info.h
new file mode 100644
index 000000000..3edbef737
--- /dev/null
+++ b/src/theory/bags/infer_info.h
@@ -0,0 +1,128 @@
+/*********************                                                        */
+/*! \file infer_info.h
+ ** \verbatim
+ ** Top contributors (to current version):
+ **   Mudathir Mohamed
+ ** This file is part of the CVC4 project.
+ ** Copyright (c) 2009-2020 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 Inference information utility
+ **/
+
+#include "cvc4_private.h"
+
+#ifndef CVC4__THEORY__BAGS__INFER_INFO_H
+#define CVC4__THEORY__BAGS__INFER_INFO_H
+
+#include <map>
+#include <vector>
+
+#include "expr/node.h"
+#include "theory/theory_inference.h"
+
+namespace CVC4 {
+namespace theory {
+namespace bags {
+
+/**
+ * Types of inferences used in the procedure
+ */
+enum class Inference : uint32_t
+{
+  NONE,
+  BAG_MK_BAG,
+  BAG_EQUALITY,
+  BAG_DISEQUALITY,
+  BAG_EMPTY,
+  BAG_UNION_DISJOINT,
+  BAG_UNION_MAX,
+  BAG_INTERSECTION_MIN,
+  BAG_DIFFERENCE_SUBTRACT,
+  BAG_DIFFERENCE_REMOVE,
+  BAG_DUPLICATE_REMOVAL
+};
+
+/**
+ * Converts an inference to a string. Note: This function is also used in
+ * `safe_print()`. Changing this functions name or signature will result in
+ * `safe_print()` printing "<unsupported>" instead of the proper strings for
+ * the enum values.
+ *
+ * @param i The inference
+ * @return The name of the inference
+ */
+const char* toString(Inference i);
+
+/**
+ * Writes an inference name to a stream.
+ *
+ * @param out The stream to write to
+ * @param i The inference to write to the stream
+ * @return The stream
+ */
+std::ostream& operator<<(std::ostream& out, Inference i);
+
+class InferenceManager;
+
+/**
+ * An inference. This is a class to track an unprocessed call to either
+ * send a fact, lemma, or conflict that is waiting to be asserted to the
+ * equality engine or sent on the output channel.
+ */
+class InferInfo : public TheoryInference
+{
+ public:
+  InferInfo();
+  ~InferInfo() {}
+  /** Process this inference */
+  bool process(TheoryInferenceManager* im, bool asLemma) override;
+  /** The inference identifier */
+  Inference d_id;
+  /** The conclusion */
+  Node d_conclusion;
+  /**
+   * The premise(s) of the inference, interpreted conjunctively. These are
+   * literals that currently hold in the equality engine.
+   */
+  std::vector<Node> d_premises;
+
+  /**
+   * A list of new skolems introduced as a result of this inference. They
+   * are mapped to by a length status, indicating the length constraint that
+   * can be assumed for them.
+   */
+  std::vector<Node> d_newSkolem;
+  /**  Is this infer info trivial? True if d_conc is true. */
+  bool isTrivial() const;
+  /**
+   * Does this infer info correspond to a conflict? True if d_conc is false
+   * and it has no new premises (d_noExplain).
+   */
+  bool isConflict() const;
+  /**
+   * Does this infer info correspond to a "fact". A fact is an inference whose
+   * conclusion should be added as an equality or predicate to the equality
+   * engine with no new external premises (d_noExplain).
+   */
+  bool isFact() const;
+  /** Get premises */
+  Node getPremises() const;
+};
+
+/**
+ * Writes an inference info to a stream.
+ *
+ * @param out The stream to write to
+ * @param ii The inference info to write to the stream
+ * @return The stream
+ */
+std::ostream& operator<<(std::ostream& out, const InferInfo& ii);
+
+}  // namespace bags
+}  // namespace theory
+}  // namespace CVC4
+
+#endif /* CVC4__THEORY__BAGS__INFER_INFO_H */