accumulator.hh

// Copyright (C) 2007, 2008, 2009 EPITA Research and Development Laboratory (LRDE)
//
// This file is part of Olena.
//
// Olena is free software: you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free
// Software Foundation, version 2 of the License.
//
// Olena is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Olena.  If not, see <http://www.gnu.org/licenses/>.
//
// As a special exception, you may use this file as part of a free
// software project without restriction.  Specifically, if other files
// instantiate templates or use macros or inline functions from this
// file, or you compile this file and link it with other files to produce
// an executable, this file does not by itself cause the resulting
// executable to be covered by the GNU General Public License.  This
// exception does not however invalidate any other reasons why the
// executable file might be covered by the GNU General Public License.

#ifndef MLN_CORE_CONCEPT_ACCUMULATOR_HH
# define MLN_CORE_CONCEPT_ACCUMULATOR_HH


# include <mln/core/concept/proxy.hh>
# include <mln/metal/fix_return.hh>
# include <mln/metal/const.hh>
# include <mln/trait/accumulators.hh>


namespace mln
{

  // Forward declaration.
  template <typename E> struct Accumulator;


  namespace convert
  {

    namespace over_load
    {

      template <typename A>
      void
      from_to_(const Accumulator<A>& from, mln_result(A)& to);

    } // end of namespace mln::convert::over_load

  } // end of namespace mln::convert


  // Accumulator category flag type.
  template <>
  struct Accumulator<void>
  {
    typedef Proxy<void> super;
  };



  template <typename E>
  struct Accumulator : public Proxy<E>
  {
    typedef Accumulator<void> category;

    /*
      typedef argument;
      typedef result;
      typedef q_result;

      void init();
      void take(const argument& t);
      void take(const E& other);

      q_result to_result() const;
      operator q_result const;

      bool is_valid() const;
     */

    template <typename T>
    void take_as_init(const T& t); // 't' is either argument or E.

    template <typename T>
    void take_as_init_(const T& t);


    template <typename T>
    void take_n_times(unsigned n, const T& t);

    template <typename T>
    void take_n_times_(unsigned n, const T& t);

    
  protected:
    Accumulator();
  };


# ifndef MLN_INCLUDE_ONLY


  // convert::from_to_

  namespace convert
  {

    namespace over_load
    {

      template <typename A>
      void
      from_to_(const Accumulator<A>& from_, mln_result(A)& to)
      {
        const A& from = exact(from_);
        if (from.is_valid())
          to = from.to_result();
        else
          to = mln_result(A)();
      }

    } // end of namespace mln::convert::over_load

  } // end of namespace mln::convert



  // Accumulator<E>

  template <typename E>
  inline
  Accumulator<E>::Accumulator()
  {
    typedef mln_argument(E) argument;
    typedef mln_result(E)   result;
    typedef mln_q_result(E) q_result;

    void (E::*m1)() = & E::init;
    m1 = 0;
    void (E::*m2)(const argument&) = & E::take;
    m2 = 0;
    void (E::*m3)(const E&) = & E::take;
    m3 = 0;

    q_result (E::*m4)() const = & E::to_result;
    m4 = 0;
    q_result (E::*m5)() const = & E::operator q_result;
    m5 = 0;

    bool (E::*m6)() const = & E::is_valid;
    m6 = 0;
  }


  // take_as_init

  template <typename E>
  template <typename T>
  void
  Accumulator<E>::take_as_init(const T& t)
  {
    typedef mln_exact(T) T_;
    typedef mlc_converts_to(T_, mln_argument(E)) t_is_argument;
    typedef mlc_converts_to(T_, E)               t_is_accumulator;
    mlc_or(t_is_argument, t_is_accumulator)::check();

    // Dispatch.
    exact(this)->take_as_init_(t);
  }

  template <typename E>
  template <typename T>
  void
  Accumulator<E>::take_as_init_(const T& t)
  {
    // Default impl.
    exact(this)->init();
    exact(this)->take(t);
  }


  // take n times

  template <typename E>
  template <typename T>
  void
  Accumulator<E>::take_n_times(unsigned n, const T& t)
  {
    typedef mln_exact(T) T_;
    typedef mlc_converts_to(T_, mln_argument(E)) t_is_argument;
    typedef mlc_converts_to(T_, E)               t_is_accumulator;
    mlc_or(t_is_argument, t_is_accumulator)::check();

    if (n == 0u)
      return;

    // Dispatch.
    exact(this)->take_n_times_(n, t);
  }

  template <typename E>
  template <typename T>
  void
  Accumulator<E>::take_n_times_(unsigned n, const T& t)
  {
    // Default impl.
    for (unsigned i = 0; i < n; ++i)
      exact(this)->take(t);
  }

# endif // ! MLN_INCLUDE_ONLY

} // end of namespace mln


#endif // ! MLN_CORE_CONCEPT_ACCUMULATOR_HH