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/* Copyright (c) 2002,2003,2005 CrystalClear Software, Inc.
 * Use, modification and distribution is subject to the 
 * Boost Software License, Version 1.0. (See accompanying
 * file LICENSE_1_0.txt or
 * Author: Jeff Garland, Bart Garst

namespace boost {
namespace date_time {

    //! Defines base interface for calculating start and end date of daylight savings 
    template<class date_type>
    class dst_day_calc_rule 
      typedef typename date_type::year_type year_type;
      virtual ~dst_day_calc_rule() {}
      virtual date_type start_day(year_type y) const=0;
      virtual std::string start_rule_as_string() const=0;
      virtual date_type end_day(year_type y) const=0;
      virtual std::string end_rule_as_string() const=0;


    //! Canonical form for a class that provides day rule calculation
    /*! This class is used to generate specific sets of dst rules
     *@param spec Provides a specifiction of the function object types used
     *            to generate start and end days of daylight savings as well
     *            as the date type.
    template<class spec>
    class day_calc_dst_rule : public dst_day_calc_rule<typename spec::date_type>
      typedef typename spec::date_type date_type;
      typedef typename date_type::year_type year_type;
      typedef typename spec::start_rule start_rule;
      typedef typename spec::end_rule  end_rule;
      day_calc_dst_rule(start_rule dst_start,
                        end_rule dst_end) :
      virtual date_type start_day(year_type y) const
        return dst_start_.get_date(y);
      virtual std::string start_rule_as_string() const
        return dst_start_.to_string();
      virtual date_type end_day(year_type y) const
        return dst_end_.get_date(y);
      virtual std::string end_rule_as_string() const
        return dst_end_.to_string();
      start_rule dst_start_;
      end_rule dst_end_;

} }//namespace