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# krat_coefficient.hxx

    00001 // krat_coefficient.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_ALGEBRA_IMPLEMENTATION_SERIES_KRAT_COEFFICIENT_HXX
    00018 # define VCSN_ALGEBRA_IMPLEMENTATION_SERIES_KRAT_COEFFICIENT_HXX
    00019
    00020 # include <utility>
    00021 # include <vaucanson/algorithms/krat_exp_constant_term.hh>
    00022 # include <vaucanson/algebra/implementation/series/krat_exp_pattern.hh>
    00023
    00024 namespace vcsn {
    00025
    00026   namespace algebra {
    00027
    00028     template <class Series, class T, class Dispatch>
    00029     class CoefficientEval : public algebra::KRatExpMatcher<
    00030       CoefficientEval<Series, T, Dispatch>,
    00031       T,
    00032       std::pair<typename Element<Series, T>::semiring_elt_t,
    00033                 Element<Series, T> >,
    00034       Dispatch
    00035       >
    00036     {
    00037     public:
    00038       typedef ConstantTermEval<Series, T, Dispatch>     self_t;
    00039       typedef typename Element<Series, T>::semiring_elt_t     semiring_elt_t;
    00040       typedef std::pair<semiring_elt_t, Element<Series, T> >  return_type;
    00041       typedef typename semiring_elt_t::value_t          semiring_elt_value_t;
    00042       INHERIT_CONSTRUCTORS(self_t, T, semiring_elt_t, Dispatch);
    00043
    00044       CoefficientEval(const Element<Series, T>& exp) :
    00045         exp_(exp)
    00046       {}
    00047
    00048       semiring_elt_t    one()
    00049       {
    00050         return
    00051           exp_.structure().semiring().identity(SELECT(semiring_elt_value_t));
    00052       }
    00053
    00054       semiring_elt_t zero()
    00055       {
    00056         return
    00057           exp_.structure().semiring().zero(SELECT(semiring_elt_value_t));
    00058       }
    00059
    00060       MATCH__(Product, lhs, rhs)
    00061       {
    00062         return return_type(one(), lhs * rhs);
    00063       }
    00064       END
    00065
    00066       MATCH__(Sum, lhs, rhs)
    00067       {
    00068         return return_type(one(), lhs + rhs);
    00069       }
    00070       END
    00071
    00072       MATCH_(Star, node)
    00073       {
    00074         return return_type(one(), node.star());
    00075       }
    00076       END
    00077
    00078       MATCH__(LeftWeight, w, node)
    00079       {
    00080         return return_type(w, node);
    00081       }
    00082       END
    00083
    00084       MATCH__(RightWeight, node, w)
    00085       {
    00086         return return_type(w, node);
    00087       }
    00088       END
    00089
    00090       MATCH_(Constant, m)
    00091       {
    00092         return return_type(one(), m);
    00093       }
    00094       END
    00095
    00096       MATCH(Zero)
    00097       {
    00098         return return_type(zero(), zero_as<T>::of(exp_.structure()));
    00099       }
    00100       END
    00101
    00102       MATCH(One)
    00103       {
    00104         return return_type(one(), identity_as<T>::of(exp_.structure()));
    00105       }
    00106       END
    00107
    00108     private:
    00109       Element<Series, T> exp_;
    00110     };
    00111
    00112     template <class Series, class T>
    00113     std::pair<typename Element<Series, T>::semiring_elt_t, Element<Series, T> >
    00114     coefficient(const Element<Series, T>& exp)
    00115     {
    00116       CoefficientEval<Series, T, algebra::DispatchFunction<T> > matcher(exp);
    00117       return matcher.match(exp.value());
    00118     }
    00119
    00120   } // algebra
    00121
    00122 } // vcsn
    00123
    00124 #endif // ! VCSN_ALGEBRA_IMPLEMENTATION_SERIES_KRAT_COEFFICIENT_HXX