Add simple substitution utility (#5397)

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

2 files changed, 262 insertions, 0 deletions

diff --git a/src/expr/subs.cpp b/src/expr/subs.cpp
new file mode 100644
index 000000000..541db1ac5
--- /dev/null
+++ b/src/expr/subs.cpp
@@ -0,0 +1,177 @@
+/*********************                                                        */
+/*! \file subs.cpp
+ ** \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
+ **/
+
+#include "expr/subs.h"
+
+#include "theory/rewriter.h"
+
+namespace CVC4 {
+
+bool Subs::empty() const { return d_vars.empty(); }
+
+size_t Subs::size() const { return d_vars.size(); }
+
+bool Subs::contains(Node v) const
+{
+  return std::find(d_vars.begin(), d_vars.end(), v) != d_vars.end();
+}
+
+Node Subs::getSubs(Node v) const
+{
+  std::vector<Node>::const_iterator it =
+      std::find(d_vars.begin(), d_vars.end(), v);
+  if (it == d_vars.end())
+  {
+    return Node::null();
+  }
+  size_t i = std::distance(d_vars.begin(), it);
+  Assert(i < d_subs.size());
+  return d_subs[i];
+}
+
+void Subs::add(Node v)
+{
+  // default, use a fresh skolem of the same type
+  Node s = NodeManager::currentNM()->mkSkolem("sk", v.getType());
+  add(v, s);
+}
+
+void Subs::add(const std::vector<Node>& vs)
+{
+  for (const Node& v : vs)
+  {
+    add(v);
+  }
+}
+
+void Subs::add(Node v, Node s)
+{
+  Assert(v.getType().isComparableTo(s.getType()));
+  d_vars.push_back(v);
+  d_subs.push_back(s);
+}
+
+void Subs::add(const std::vector<Node>& vs, const std::vector<Node>& ss)
+{
+  Assert(vs.size() == ss.size());
+  for (size_t i = 0, nvs = vs.size(); i < nvs; i++)
+  {
+    add(vs[i], ss[i]);
+  }
+}
+
+void Subs::addEquality(Node eq)
+{
+  Assert(eq.getKind() == kind::EQUAL);
+  add(eq[0], eq[1]);
+}
+
+void Subs::append(Subs& s)
+{
+  // add the substitution list
+  add(s.d_vars, s.d_subs);
+}
+
+Node Subs::apply(Node n, bool doRewrite) const
+{
+  if (d_vars.empty())
+  {
+    return n;
+  }
+  Node ns =
+      n.substitute(d_vars.begin(), d_vars.end(), d_subs.begin(), d_subs.end());
+  if (doRewrite)
+  {
+    ns = theory::Rewriter::rewrite(ns);
+  }
+  return ns;
+}
+Node Subs::rapply(Node n, bool doRewrite) const
+{
+  if (d_vars.empty())
+  {
+    return n;
+  }
+  Node ns =
+      n.substitute(d_subs.begin(), d_subs.end(), d_vars.begin(), d_vars.end());
+  if (doRewrite)
+  {
+    ns = theory::Rewriter::rewrite(ns);
+  }
+  return ns;
+}
+
+void Subs::applyToRange(Subs& s, bool doRewrite) const
+{
+  if (d_vars.empty())
+  {
+    return;
+  }
+  for (size_t i = 0, ns = s.d_subs.size(); i < ns; i++)
+  {
+    s.d_subs[i] = apply(s.d_subs[i], doRewrite);
+  }
+}
+
+void Subs::rapplyToRange(Subs& s, bool doRewrite) const
+{
+  if (d_vars.empty())
+  {
+    return;
+  }
+  for (size_t i = 0, ns = s.d_subs.size(); i < ns; i++)
+  {
+    s.d_subs[i] = rapply(s.d_subs[i], doRewrite);
+  }
+}
+
+Node Subs::getEquality(size_t i) const
+{
+  Assert(i < d_vars.size());
+  return d_vars[i].eqNode(d_subs[i]);
+}
+
+std::map<Node, Node> Subs::toMap() const
+{
+  std::map<Node, Node> ret;
+  for (size_t i = 0, nvs = d_vars.size(); i < nvs; i++)
+  {
+    ret[d_vars[i]] = d_subs[i];
+  }
+  return ret;
+}
+
+std::string Subs::toString() const
+{
+  std::stringstream ss;
+  ss << "[";
+  for (size_t i = 0, nvs = d_vars.size(); i < nvs; i++)
+  {
+    if (i > 0)
+    {
+      ss << " ";
+    }
+    ss << d_vars[i] << " -> " << d_subs[i];
+  }
+  ss << "]";
+  return ss.str();
+}
+
+std::ostream& operator<<(std::ostream& out, const Subs& s)
+{
+  out << s.toString();
+  return out;
+}
+
+}  // namespace CVC4
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 */