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# krat_exp_derivation.hxx

    00001 // krat_exp_derivation.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, 2005 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_KRAT_EXP_DERIVATION_HXX
    00018 # define VCSN_ALGORITHMS_KRAT_EXP_DERIVATION_HXX
    00019
    00020 # include <vaucanson/algorithms/krat_exp_derivation.hh>
    00021
    00022 # include <vaucanson/algebra/implementation/series/krat_exp_pattern.hh>
    00023 # include <vaucanson/algorithms/krat_exp_constant_term.hh>
    00024
    00025 namespace vcsn {
    00026
    00027   template <class Series, class T, class Dispatch>
    00028   struct KRatExpDerivation : algebra::KRatExpMatcher<
    00029     KRatExpDerivation<Series, T, Dispatch>,
    00030     T,
    00031     Element<Series, T>,
    00032     Dispatch
    00033     >
    00034   {
    00035     typedef KRatExpDerivation<Series, T, Dispatch>    self_t;
    00036     typedef Element<Series, T>                        return_type;
    00037     typedef typename Element<Series, T>::semiring_elt_t     semiring_elt_t;
    00038     typedef typename semiring_elt_t::value_t                  semiring_elt_value_t;
    00039     typedef typename Element<Series, T>::monoid_elt_t monoid_elt_t;
    00040     typedef typename monoid_elt_t::value_t            monoid_elt_value_t;
    00041     typedef typename monoid_elt_t::set_t              monoid_t;
    00042     typedef typename monoid_t::alphabet_t             alphabet_t;
    00043     typedef typename alphabet_t::letter_t             letter_t;
    00044     INHERIT_CONSTRUCTORS(self_t, T, semiring_elt_t, Dispatch);
    00045
    00046     KRatExpDerivation(const Element<Series, T>& exp,
    00047                    letter_t                  a) :
    00048       undefined(false),
    00049       exp_(exp),
    00050       a_(a)
    00051     {}
    00052
    00053     Element<Series, T> series(const T& e)
    00054     {
    00055       return Element<Series, T>(exp_.structure(), e);
    00056     }
    00057
    00058     MATCH__(Product, lhs, rhs)
    00059     {
    00060       std::pair<semiring_elt_t, bool> ret = constant_term(series(lhs));
    00061       if (ret.second == false)
    00062         {
    00063           undefined = true;
    00064           return return_type(exp_.structure());
    00065         }
    00066       return (match(lhs) * rhs) + ret.first * match(rhs);
    00067     }
    00068     END
    00069
    00070     MATCH__(Sum, lhs, rhs)
    00071     {
    00072       return match(lhs) + match(rhs);
    00073     }
    00074     END
    00075
    00076     MATCH_(Star, e)
    00077     {
    00078       std::pair<semiring_elt_t, bool> ret = constant_term(series(e));
    00079       if ((ret.second == false) || (ret.first.starable() == false))
    00080         {
    00081           undefined = true;
    00082           return return_type(exp_.structure());
    00083         }
    00084       return ret.first.star() * match(e) * e.clone().star();
    00085     }
    00086     END
    00087
    00088     MATCH__(LeftWeight, w, e)
    00089     {
    00090       return semiring_elt_t(w) * match(e);
    00091     }
    00092     END
    00093
    00094     MATCH__(RightWeight, e, w)
    00095     {
    00096       return match(e) * semiring_elt_t(w);
    00097     }
    00098     END
    00099
    00100     MATCH_(Constant, m)
    00101     {
    00102       if (m[0] == a_)
    00103         {
    00104           if (m.length() == 1)
    00105             return algebra::identity_as<T>::of(exp_.structure());
    00106           else
    00107             return Element<Series, T> (exp_.structure(), m.substr(1));
    00108         }
    00109       else
    00110         return algebra::zero_as<T>::of(exp_.structure());
    00111     }
    00112     END
    00113
    00114     MATCH(Zero)
    00115     {
    00116       return algebra::zero_as<T>::of(exp_.structure());
    00117     }
    00118     END
    00119
    00120     MATCH(One)
    00121     {
    00122       return algebra::zero_as<T>::of(exp_.structure());
    00123     }
    00124     END
    00125
    00126     bool undefined;
    00127
    00128   private:
    00129     Element<Series, T>  exp_;
    00130     letter_t            a_;
    00131   };
    00132
    00133   template <class Series, class T, class Letter>
    00134   std::pair<Element<Series, T>, bool>
    00135   derivate(const Element<Series, T>& exp,
    00136            Letter a)
    00137   {
    00138     KRatExpDerivation<Series, T, algebra::DispatchFunction<T> >
    00139       matcher(exp, a);
    00140     Element<Series, T> ret = matcher.match(exp.value());
    00141     if (matcher.undefined)
    00142       return std::make_pair(ret, false);
    00143     return std::make_pair(ret, true);
    00144   }
    00145
    00146   template <class Series, class T, class Word>
    00147   std::pair<Element<Series, T>, bool>
    00148   word_derivate(const Element<Series, T>& exp,
    00149                 Word w)
    00150   {
    00151     Element<Series, T> ret(exp);
    00152     for (typename Word::reverse_iterator a = w.rbegin();
    00153          a != w.rend(); ++a)
    00154       {
    00155         KRatExpDerivation<Series, T, algebra::DispatchFunction<T> >
    00156           matcher(exp, *a);
    00157         ret = matcher.match(ret.value());
    00158         if (matcher.undefined)
    00159           return std::make_pair(ret, false);
    00160       }
    00161     return std::make_pair(ret, true);
    00162   }
    00163
    00164 } // vcsn
    00165
    00166 #endif // ! VCSN_ALGORITHMS_KRAT_EXP_DERIVATION_HXX