// Copyright (C) 2013 Laboratoire de Recherche et Developpement de
// l'Epita (LRDE).
//
// 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/>.

#ifndef SPOT_LTLVISIT_REMOVE_X_HH
# define SPOT_LTLVISIT_REMOVE_X_HH

namespace spot
{
  namespace ltl
  {
    class formula;

    /// \brief Rewrite a stutter-insensitive formula \a f without
    /// using the X operator.
    ///
    /// This function may also be applied to stutter-sensitive formulas,
    /// but in that case the resulting formula is not equivalent.
    ///
    /// \verbatim
    /// @Article{         etessami.00.ipl,
    ///   author        = {Kousha Etessami},
    ///   title         = {A note on a question of {P}eled and {W}ilke regarding
    ///                   stutter-invariant {LTL}},
    ///   journal       = {Information Processing Letters},
    ///   volume        = {75},
    ///   number        = {6},
    ///   year          = {2000},
    ///   pages         = {261--263}
    /// }
    /// \endverbatim
    const formula* remove_x(const formula* f);

    /// \brief Whether an LTL formula \a f is stutter-insensitive.
    ///
    /// This is simply achieved by checking whether the output of
    /// <code>remove_x(f)</code> is equivalent to \a f.  This only
    /// works for LTL formulas, not PSL formulas.
    ///
    /// \verbatim
    /// @Article{         etessami.00.ipl,
    ///   author        = {Kousha Etessami},
    ///   title         = {A note on a question of {P}eled and {W}ilke regarding
    ///                   stutter-invariant {LTL}},
    ///   journal       = {Information Processing Letters},
    ///   volume        = {75},
    ///   number        = {6},
    ///   year          = {2000},
    ///   pages         = {261--263}
    /// }
    /// \endverbatim
    bool is_stutter_insensitive(const formula* f);
  }
}

#endif // SPOT_LTLVISIT_ETESSAMI00_HH