maximal_closed_subformula.h

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// Author(s): Wieger Wesselink
// Copyright: see the accompanying file COPYING or copy at
// https://github.com/mCRL2org/mCRL2/blob/master/COPYING
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
/// \file mcrl2/modal_formula/maximal_closed_subformula.h
/// \brief add your file description here.
 
#ifndef MCRL2_MODAL_FORMULA_MAXIMAL_CLOSED_SUBFORMULA_H
#define MCRL2_MODAL_FORMULA_MAXIMAL_CLOSED_SUBFORMULA_H
 
#include "mcrl2/modal_formula/traverser.h"
 
namespace mcrl2::state_formulas
{
 
namespace detail {
 
inline
std::size_t child_count(const state_formula& x)
{
  if (data::is_data_expression(x))            { return 0; }
  else if (state_formulas::is_true(x))        { return 0; }
  else if (state_formulas::is_false(x))       { return 0; }
  else if (state_formulas::is_not(x))         { return 1; }
  else if (state_formulas::is_and(x))         { return 2; }
  else if (state_formulas::is_or(x))          { return 2; }
  else if (state_formulas::is_imp(x))         { return 2; }
  else if (state_formulas::is_forall(x))      { return 1; }
  else if (state_formulas::is_exists(x))      { return 1; }
  else if (state_formulas::is_must(x))        { return 1; }
  else if (state_formulas::is_may(x))         { return 1; }
  else if (state_formulas::is_yaled(x))       { return 0; }
  else if (state_formulas::is_yaled_timed(x)) { return 0; }
  else if (state_formulas::is_delay(x))       { return 0; }
  else if (state_formulas::is_delay_timed(x)) { return 0; }
  else if (state_formulas::is_variable(x))    { return 0; }
  else if (state_formulas::is_nu(x))          { return 1; }
  else if (state_formulas::is_mu(x))          { return 1; }
  throw mcrl2::runtime_error("child_count: unknown argument");
  return 0;
}
 
template <template <class> class Traverser, class Node, class Derived>
struct bottom_up_traverser: public Traverser<Derived>
{
  using super = Traverser<Derived>;
  using super::enter;
  using super::apply;
 
  Derived& derived()
  {
    return static_cast<Derived&>(*this);
  }
 
  // Maintain a stack with nodes, used to store intermediate results
  std::vector<Node> node_stack;
  using node_iterator = typename std::vector<Node>::const_iterator;
 
  // Push a node to node_stack
  void push(const Node& node)
  {
    node_stack.push_back(node);
    mCRL2log(log::debug) << "<push>" << node << std::endl;
  }
 
  // Pop the top element of node_stack and return it
  Node pop()
  {
    Node result = node_stack.back();
    node_stack.pop_back();
    return result;
  }
 
  // Return the top element of node_stack
  Node& top()
  {
    return node_stack.back();
  }
 
  // Return the top element of node_stack
  const Node& top() const
  {
    return node_stack.back();
  }
 
  template <typename T>
  void join(const T& /* x */, node_iterator /* first */, node_iterator /* last */, Node& /* result */)
  {
  }
 
  // Override the leave function, such that it combines the results of child nodes
  template <typename T>
  void leave(const T& x)
  {
    Node result;
    std::size_t n = child_count(atermpp::down_cast<state_formula>(x));
    derived().join(x, node_stack.end() - n, node_stack.end(), result);
    node_stack.erase(node_stack.end() - n, node_stack.end());
    push(result);
  }
 
  // This leave function needs to be disabled.
  // TODO: It seems more logical that the call to this leave function is not generated in
  // the traverser, to avoid that the same term is visited twice.
  void leave(const state_formulas::state_formula&)
  {
  }
};
 
struct free_variables_node
{
  std::set<data::variable> variables;
 
  free_variables_node(const std::set<data::variable>& variables_ = std::set<data::variable>())
    : variables(variables_)
  { }
};
 
struct maximal_closed_subformula_node: public free_variables_node
{
  std::set<state_formulas::state_formula> formulas;
 
  maximal_closed_subformula_node(const std::set<data::variable>& variables = std::set<data::variable>(),
                                 const std::set<state_formulas::state_formula>& formulas_ = std::set<state_formulas::state_formula>()
                                )
    : free_variables_node(variables),
      formulas(formulas_)
  { }
};
 
inline std::ostream& operator<<(std::ostream& out, const maximal_closed_subformula_node& node)
{
  out << "<node>variables = ";
  for (const data::variable& v: node.variables)
  {
    out << v << " ";
  }
  out << " formulas = ";
  for (const state_formula& f: node.formulas)
  {
    out << f << " ";
  }
  return out;
}
 
template <typename Derived>
struct maximal_closed_subformula_traverser: public bottom_up_traverser<state_formulas::state_formula_traverser, maximal_closed_subformula_node, Derived>
{
  using super = bottom_up_traverser<state_formulas::state_formula_traverser, maximal_closed_subformula_node, Derived>;
  using super::enter;
  using super::leave;
  using super::apply;
  using super::push;
  using super::pop;
  using super::top;
  using super::node_stack;
 
  using node_iterator = typename super::node_iterator;
 
  Derived& derived()
  {
    return static_cast<Derived&>(*this);
  }
 
  template <typename T>
  void update_free_variables(const T& /* x */, maximal_closed_subformula_node& /* result */)
  { }
 
  void update_free_variables(const data::data_expression& x, maximal_closed_subformula_node& result)
  {
    data::find_free_variables(x, std::inserter(result.variables, result.variables.end()));
  }
 
  void update_free_variables(const state_formulas::forall& x, maximal_closed_subformula_node& result)
  {
    for (const data::variable& v: x.variables())
    {
      result.variables.erase(v);
    }
  }
 
  void update_free_variables(const state_formulas::exists& x, maximal_closed_subformula_node& result)
  {
    for (const data::variable& v: x.variables())
    {
      result.variables.erase(v);
    }
  }
 
  void update_free_variables(const state_formulas::variable& x, maximal_closed_subformula_node& result)
  {
    for (const data::data_expression& e: x.arguments())
    {
      data::find_free_variables(e, std::inserter(result.variables, result.variables.end()));
    }
  }
 
  template <typename T>
  void update_maximal_closed_formulas(const T& x, maximal_closed_subformula_node& result)
  {
    if (result.variables.empty())
    {
      result.formulas.clear();
      result.formulas.insert(x);
    }
  }
 
  template <typename T>
  void join(const T& x, node_iterator first, node_iterator last, maximal_closed_subformula_node& result)
  {
    for (node_iterator i = first; i != last; ++i)
    {
      result.variables.insert(i->variables.begin(), i->variables.end());
    }
    update_free_variables(x, result);
    if (result.variables.empty())
    {
      result.formulas.insert(atermpp::down_cast<state_formula>(x));
    }
    else
    {
      for (node_iterator i = first; i != last; ++i)
      {
        result.formulas.insert(i->formulas.begin(), i->formulas.end());
      }
    }
  }
};
 
struct apply_maximal_closed_subformula_traverser: public maximal_closed_subformula_traverser<apply_maximal_closed_subformula_traverser>
{
  using super = maximal_closed_subformula_traverser<apply_maximal_closed_subformula_traverser>;
  using super::enter;
  using super::leave;
  using super::apply;
  using super::top;
};
 
}; // namespace detail
 
inline
std::set<state_formulas::state_formula> maximal_closed_subformulas(const state_formula& x)
{
  detail::apply_maximal_closed_subformula_traverser f;
  f.apply(x);
  return f.top().formulas;
}
 
} // namespace mcrl2::state_formulas
 
#endif // MCRL2_MODAL_FORMULA_MAXIMAL_CLOSED_SUBFORMULA_H