Add simple substitution utility (#5397)

A few new algorithms for CEGQI and single invocation sygus will use this utility for managing transformations.

1 files changed, 85 insertions, 0 deletions

diff --git a/src/expr/subs.h b/src/expr/subs.h
new file mode 100644
index 000000000..ac678d2ee
--- /dev/null
+++ b/src/expr/subs.h
@@ -0,0 +1,85 @@
+/*********************                                                        */
+/*! \file subs.h
+ ** \verbatim
+ ** Top contributors (to current version):
+ **   Andrew Reynolds
+ ** 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 Simple substitution utility
+ **/
+
+#ifndef CVC4__EXPR__SUBS_H
+#define CVC4__EXPR__SUBS_H
+
+#include <map>
+#include <vector>
+#include "expr/node.h"
+
+namespace CVC4 {
+
+/**
+ * Helper substitution class. Stores a substitution in parallel vectors
+ * d_vars and d_subs, both of which may be arbitrary terms, having the same
+ * types pairwise.
+ *
+ * Notice this class applies substitutions using Node::substitute. Furthermore,
+ * it does not insist that the terms in d_vars are unique.
+ */
+class Subs
+{
+ public:
+  /** Is the substitution empty? */
+  bool empty() const;
+  /** The size of the substitution */
+  size_t size() const;
+  /** Does the substitution contain v? */
+  bool contains(Node v) const;
+  /** Get the substitution for v if it exists, or null otherwise */
+  Node getSubs(Node v) const;
+  /** Add v -> k for fresh skolem of the same type as v */
+  void add(Node v);
+  /** Add v -> k for fresh skolem of the same type as v for each v in vs */
+  void add(const std::vector<Node>& vs);
+  /** Add v -> s to the substitution */
+  void add(Node v, Node s);
+  /** Add vs -> ss to the substitution */
+  void add(const std::vector<Node>& vs, const std::vector<Node>& ss);
+  /** Add eq[0] -> eq[1] to the substitution */
+  void addEquality(Node eq);
+  /** Append the substitution s to this */
+  void append(Subs& s);
+  /** Return the result of this substitution on n */
+  Node apply(Node n, bool doRewrite = false) const;
+  /** Return the result of the reverse of this substitution on n */
+  Node rapply(Node n, bool doRewrite = false) const;
+  /** Apply this substitution to all nodes in the range of s */
+  void applyToRange(Subs& s, bool doRewrite = false) const;
+  /** Apply the reverse of this substitution to all nodes in the range of s */
+  void rapplyToRange(Subs& s, bool doRewrite = false) const;
+  /** Get equality (= v s) where v -> s is the i^th position in the vectors */
+  Node getEquality(size_t i) const;
+  /** Convert substitution to map */
+  std::map<Node, Node> toMap() const;
+  /** Get string for this substitution */
+  std::string toString() const;
+  /** The data */
+  std::vector<Node> d_vars;
+  std::vector<Node> d_subs;
+};
+
+/**
+ * Serializes a given substitution to the given stream.
+ *
+ * @param out the output stream to use
+ * @param s the substitution to output to the stream
+ * @return the stream
+ */
+std::ostream& operator<<(std::ostream& out, const Subs& s);
+
+}  // namespace CVC4
+
+#endif /* CVC4__EXPR__SUBS_H */