simplify_rewriter.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)
//
 
#ifndef MCRL2_PBES_REWRITERS_SIMPLIFY_REWRITER_H
#define MCRL2_PBES_REWRITERS_SIMPLIFY_REWRITER_H
 
#include "mcrl2/pbes/rewriters/data_rewriter.h"
 
namespace mcrl2 {
 
namespace pbes_system {
 
namespace detail {
 
template <template <class> class Builder, class Derived>
struct add_simplify: public Builder<Derived>
{
  typedef Builder<Derived> super;
  using super::apply;
 
  template <class T>
  void apply(T& result, const not_& x)
  {
    assert(&result!=&x);  // Result is used as temporary store and cannot match x. 
    apply(result, x.operand());
    if (is_false(result))
    {
      result = true_();
      return;
    }
    if (is_true(result))
    {
      result = false_();
      return;
    }
    if (is_not(result))
    {
      result = atermpp::down_cast<not_>(result).operand();
      return;
    }
    make_not_(result, result);
  }
 
  template <class T>
  void apply(T& result, const and_& x)
  {
    assert(&result!=&x);  // Result is used as temporary store and cannot match x. 
    apply(result, x.left());
    if (is_false(result))
    {
      result = false_();
      return;
    }
    if (is_true(result))
    {
      apply(result, x.right());
      return;
    }
    pbes_expression right;
    apply(right, x.right());
    if (is_false(right))
    {
      result = false_();
      return;
    }
    if (is_true(right) || result==right)
    {
      return;
    }
    make_and_(result,result, right);
  }
 
  template <class T>
  void apply(T& result, const or_& x)
  {
    assert(&result!=&x);  // Result is used as temporary store and cannot match x. 
    apply(result, x.left());
    if (is_true(result))
    {
      result = true_();
      return;
    }
    if (is_false(result))
    {
      apply(result, x.right());
      return;
    }
    pbes_expression right;
    apply(right, x.right());
    if (is_true(right))
    {
      result = true_();
      return;
    }
    if (is_false(right) || result==right)
    {
      return;
    }
    make_or_(result,result, right);
  }
 
  template <class T>
  void apply(T& result, const imp& x)
  {
    assert(&result!=&x);  // Result is used as temporary store and cannot match x. 
    if (is_false(x.left()))  // This test is cheap. 
    {
      result = true_();
      return;
    }
    apply(result, x.right());
    if (is_true(result))
    { 
      result = true_();
      return;
    }
    if (is_false(result))
    { 
      apply(result, x.left());
      if (is_not(result))
      { 
        result = atermpp::down_cast<not_>(result).operand();
        return;
      }
      if (is_true(result))
      {
        result = false_();
        return;
      }
      if (is_false(result))
      {
        result = true_();
        return;
      }
      make_not_(result, result);
      return;
    }
    pbes_expression left;
    apply(left, x.left());
    if (is_true(left))
    { 
      return;
    }
    if (is_false(left) || result==left)
    { 
      result = true_();
      return;
    }
    make_imp(result, left, result);
  }
 
  template <class T>
  void apply(T& result, const forall& x)
  {
    apply(result, x.body());
    data::optimized_forall(result, x.variables(), result, true);
  }
 
  template <class T>
  void apply(T& result, const exists& x)
  {
    apply(result, x.body());
    data::optimized_exists(result, x.variables(), result, true);
  }
};
 
template <typename Derived>
struct simplify_builder: public add_simplify<pbes_system::pbes_expression_builder, Derived>
{ };
 
template <typename Derived, typename DataRewriter, typename SubstitutionFunction>
struct simplify_data_rewriter_builder : public add_data_rewriter < pbes_system::detail::simplify_builder, Derived, DataRewriter, SubstitutionFunction >
{
  typedef add_data_rewriter < pbes_system::detail::simplify_builder, Derived, DataRewriter, SubstitutionFunction > super;
  simplify_data_rewriter_builder(const DataRewriter& R, SubstitutionFunction& sigma)
    : super(R, sigma)
  {}
};
 
} // namespace detail
 
struct simplify_rewriter
{
  typedef pbes_expression term_type;
  typedef data::variable variable_type;
 
  pbes_expression operator()(const pbes_expression& x) const
  {
    pbes_expression result;
    core::make_apply_builder<detail::simplify_builder>().apply(result, x);
    return result;
  }
 
  void operator()(pbes_expression& result, const pbes_expression& x) const
  {
    core::make_apply_builder<detail::simplify_builder>().apply(result, x);
  }
};
 
template <typename DataRewriter>
struct simplify_data_rewriter
{
  typedef pbes_expression term_type;
  typedef data::variable variable_type;
 
  const DataRewriter& R;
 
  explicit simplify_data_rewriter(const DataRewriter& R_)
    : R(R_)
  {}
 
  pbes_expression operator()(const pbes_expression& x) const
  {
    data::no_substitution sigma;
    pbes_expression result;
    detail::make_apply_rewriter_builder<pbes_system::detail::simplify_data_rewriter_builder>(R, sigma).apply(result,x);
    return result;
  }
 
  template <typename SubstitutionFunction>
  pbes_expression operator()(const pbes_expression& x, SubstitutionFunction& sigma) const
  {
    pbes_expression result;
    detail::make_apply_rewriter_builder<pbes_system::detail::simplify_data_rewriter_builder>(R, sigma).apply(result, x);
    return result;
  }
 
  template <typename SubstitutionFunction>
  void operator()(pbes_expression& result, const pbes_expression& x, SubstitutionFunction& sigma) const
  {
    detail::make_apply_rewriter_builder<pbes_system::detail::simplify_data_rewriter_builder>(R, sigma).apply(result, x);
  }
};
 
} // namespace pbes_system
 
} // namespace mcrl2
 
#endif // MCRL2_PBES_REWRITERS_SIMPLIFY_REWRITER_H