partial_rat_exp_constant_term.hxx

00001 // partial_rat_exp_constant_term.hxx: this file is part of the Vaucanson project.
00002 //
00003 // Vaucanson, a generic library for finite state machines.
00004 //
00005 // Copyright (C) 2001, 2002, 2003, 2004 The Vaucanson Group.
00006 //
00007 // This program is free software; you can redistribute it and/or
00008 // modify it under the terms of the GNU General Public License
00009 // as published by the Free Software Foundation; either version 2
00010 // of the License, or (at your option) any later version.
00011 //
00012 // The complete GNU General Public Licence Notice can be found as the
00013 // `COPYING' file in the root directory.
00014 //
00015 // The Vaucanson Group consists of people listed in the `AUTHORS' file.
00016 //
00017 #ifndef VCSN_ALGORITHMS_INTERNAL_PARTIAL_RAT_EXP_CONSTANT_TERM_HXX
00018 # define VCSN_ALGORITHMS_INTERNAL_PARTIAL_RAT_EXP_CONSTANT_TERM_HXX
00019 
00020 # include <utility>
00021 # include <vaucanson/algorithms/internal/partial_rat_exp_constant_term.hh>
00022 # include <vaucanson/algorithms/krat_exp_constant_term.hh>
00023 
00024 namespace vcsn {
00025 
00026   template <class Series, class T>
00027   std::pair<typename Element<Series, T>::semiring_elt_t, bool>
00028   constant_term(const PartialExp<Series, T>& exp)
00029   {
00030     typedef typename PartialExp<Series, T>::const_iterator      const_iterator;
00031     typedef typename PartialExp<Series, T>::semiring_elt_t      semiring_elt_t;
00032     typedef typename PartialExp<Series, T>::series_set_elt_value_t
00033       series_set_elt_value_t;
00034     typedef std::pair<typename Element<Series, T>::semiring_elt_t, bool>
00035       result_t;
00036 
00037     const_iterator      i = exp.begin();
00038     semiring_elt_t      res = i.semiring_elt();
00039     bool                defined = true;
00040 
00041     for (i++; i != exp.end() && defined; ++i)
00042     {
00043       if (i.on_node())
00044       {
00045         result_t tmp = constant_term(
00046           Element<Series, T>(exp.exp_structure(),
00047                              series_set_elt_value_t (i.node())));
00048         defined = tmp.second;
00049         res *= tmp.first;
00050       }
00051       else
00052         res *= i.semiring_elt();
00053     }
00054     return std::make_pair(res, defined);
00055   }
00056 
00057 } // vcsn
00058 
00059 #endif // ! VCSN_ALGORITHMS_INTERNAL_PARTIAL_RAT_EXP_CONSTANT_TERM_HXX

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