spot/src/ltlvisit/lunabbrev.cc

// -*- coding: utf-8 -*-
// Copyright (C) 2009, 2010, 2012, 2014, 2015 Laboratoire de Recherche
// et Développement de l'Epita (LRDE).
// Copyright (C) 2003, 2004 Laboratoire d'Informatique de Paris 6 (LIP6),
// département Systèmes Répartis Coopératifs (SRC), Université Pierre
// et Marie Curie.
//
// This file is part of Spot, a model checking library.
//
// Spot is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
//
// Spot is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
// or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
// License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

#include "ltlast/allnodes.hh"
#include "lunabbrev.hh"
#include <cassert>

namespace spot
{
  namespace ltl
  {

    unabbreviate_logic_visitor::unabbreviate_logic_visitor(const char* opt)
    {
      while (*opt)
	switch (char c = *opt++)
	  {
	  case '^':
	    rewrite_xor = true;
	    break;
	  case 'i':
	    rewrite_i = true;
	    break;
	  case 'e':
	    rewrite_e = true;
	    break;
	  default:
	    throw std::runtime_error
	      (std::string("unknown option for unabbreviate_logic_visitor(): ")
	       + c);
	  }
    }

    unabbreviate_logic_visitor::~unabbreviate_logic_visitor()
    {
    }

    void
    unabbreviate_logic_visitor::visit(const binop* bo)
    {
      const formula* f1 = recurse(bo->first());
      const formula* f2 = recurse(bo->second());
      binop::type op = bo->op();
      switch (op)
	{
	  /* f1 ^ f2  ==  !(f1 <-> f2) */
	  /* f1 ^ f2  ==  (f1 & !f2) | (f2 & !f1) */
	case binop::Xor:
	  {
	    if (!rewrite_xor)
	      goto no_rewrite;
	    if (!rewrite_e)
	      {
		result_ = unop::instance(unop::Not,
					 binop::instance(binop::Equiv, f1, f2));
		return;
	      }
	    else
	      {
		const formula* a =
		  multop::instance(multop::And, f1->clone(),
				   unop::instance(unop::Not, f2->clone()));
		const formula* b =
		  multop::instance(multop::And, f2,
				   unop::instance(unop::Not, f1));
		result_ = multop::instance(multop::Or, a, b);
		return;
	      }
	  }
	  /* f1 => f2  ==  !f1 | f2 */
	case binop::Implies:
	  if (!rewrite_i)
	    goto no_rewrite;
	  result_ = multop::instance(multop::Or,
				     unop::instance(unop::Not, f1), f2);
	  return;
	  /* f1 <=> f2  ==  (f1 & f2) | (!f1 & !f2) */
	case binop::Equiv:
	  if (!rewrite_e)
	    goto no_rewrite;
	  {
	    const formula* f1c = f1->clone();
	    const formula* f2c = f2->clone();

	    result_ =
	      multop::instance(multop::Or,
			       multop::instance(multop::And, f1c, f2c),
			       multop::instance(multop::And,
						unop::instance(unop::Not, f1),
						unop::instance(unop::Not, f2)));
	    return;
	  }
          /* f1 U f2 == f1 U f2 */
	  /* f1 R f2 == f1 R f2 */
          /* f1 W f2 == f1 W f2 */
	  /* f1 M f2 == f1 M f2 */
	  /* f1 UConcat f2 == f1 UConcat f2 */
	  /* f1 EConcat f2 == f1 EConcat f2 */
   	case binop::U:
	case binop::R:
	case binop::W:
	case binop::M:
	case binop::UConcat:
	case binop::EConcat:
	case binop::EConcatMarked:
	  no_rewrite:
	  result_ = binop::instance(op, f1, f2);
	  return;
	}
      SPOT_UNREACHABLE();
    }

    const formula*
    unabbreviate_logic_visitor::recurse(const formula* f)
    {
      f->accept(*this);
      return result_;
    }

    const formula*
    unabbreviate_logic(const formula* f, const char* xie)
    {
      if (f->is_sugar_free_boolean())
	return f->clone();
      unabbreviate_logic_visitor v(xie);
      f->accept(v);
      return v.result();
    }
  }
}