formula.hh

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00001 // Copyright (C) 2008, 2009 Laboratoire de Recherche et Développement
00002 // de l'Epita (LRDE).
00003 // Copyright (C) 2003, 2004, 2005 Laboratoire d'Informatique de
00004 // Paris 6 (LIP6), département Systèmes Répartis Coopératifs (SRC),
00005 // Université Pierre et Marie Curie.
00006 //
00007 // This file is part of Spot, a model checking library.
00008 //
00009 // Spot is free software; you can redistribute it and/or modify it
00010 // under the terms of the GNU General Public License as published by
00011 // the Free Software Foundation; either version 2 of the License, or
00012 // (at your option) any later version.
00013 //
00014 // Spot is distributed in the hope that it will be useful, but WITHOUT
00015 // ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
00016 // or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
00017 // License for more details.
00018 //
00019 // You should have received a copy of the GNU General Public License
00020 // along with Spot; see the file COPYING.  If not, write to the Free
00021 // Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
00022 // 02111-1307, USA.
00023 
00026 #ifndef SPOT_LTLAST_FORMULA_HH
00027 # define SPOT_LTLAST_FORMULA_HH
00028 
00029 #include <string>
00030 #include <cassert>
00031 #include "predecl.hh"
00032 
00033 namespace spot
00034 {
00035   namespace ltl
00036   {
00040 
00043 
00046 
00050 
00053 
00056 
00059 
00062 
00065 
00066 
00073     class formula
00074     {
00075     public:
00076       formula() : count_(++max_count) {}
00077 
00079       virtual void accept(visitor& v) = 0;
00081       virtual void accept(const_visitor& v) const = 0;
00082 
00087       formula* clone() const;
00092       void destroy() const;
00093 
00095       virtual std::string dump() const = 0;
00096 
00098       size_t
00099       hash() const
00100       {
00101         return count_;
00102       }
00103     protected:
00104       virtual ~formula();
00105 
00107       virtual void ref_();
00110       virtual bool unref_();
00111 
00113       size_t count_;
00114 
00115     private:
00117       static size_t max_count;
00118     };
00119 
00133     struct formula_ptr_less_than:
00134       public std::binary_function<const formula*, const formula*, bool>
00135     {
00136       bool
00137       operator()(const formula* left, const formula* right) const
00138       {
00139         assert(left);
00140         assert(right);
00141         if (left == right)
00142           return false;
00143         size_t l = left->hash();
00144         size_t r = right->hash();
00145         if (l != r)
00146           return l < r;
00147         // Because the hash code assigned to each formula is the
00148         // number of formulae constructed so far, it is very unlikely
00149         // that we will ever reach a case were two different formulae
00150         // have the same hash.  This will happen only ever with have
00151         // produced 256**sizeof(size_t) formulae (i.e. max_count has
00152         // looped back to 0 and started over).  In that case we can
00153         // order two formulae by looking at their text representation.
00154         // We could be more efficient and look at their AST, but it's
00155         // not worth the burden.  (Also ordering pointers is ruled out
00156         // because it breaks the determinism of the implementation.)
00157         return left->dump() < right->dump();
00158       }
00159     };
00160 
00175     struct formula_ptr_hash:
00176       public std::unary_function<const formula*, size_t>
00177     {
00178       size_t
00179       operator()(const formula* that) const
00180       {
00181         assert(that);
00182         return that->hash();
00183       }
00184     };
00185 
00186 
00187   }
00188 }
00189 
00190 #endif // SPOT_LTLAST_FORMULA_HH

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