source: trunk/yat/utility/StrideIterator.h @ 1490

#ifndef _theplu_yat_utility_stride_iterator_
#define _theplu_yat_utility_stride_iterator_

// $Id: StrideIterator.h 1490 2008-09-11 22:10:26Z peter $

/*
  Copyright (C) 2007 Jari Häkkinen, Peter Johansson
  Copyright (C) 2008 Peter Johansson

  This file is part of the yat library, http://dev.thep.lu.se/yat

  The yat library 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; either version 3 of the
  License, or (at your option) any later version.

  The yat library 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 yat. If not, see <http://www.gnu.org/licenses/>.
*/

// debug
#include <iostream> 

#include "iterator_traits.h"

#include <boost/iterator/iterator_adaptor.hpp>

namespace theplu {
namespace yat {
namespace utility {

  // forward declaration
  template<typename Iter>
  class StrideIterator;

  /**
     Specialization for StrideIterator that calls underlying iterator.
   */
  template <typename Iter>
  struct weighted_iterator_traits<StrideIterator<Iter> > {
    /**
       StrideIterator is weighted if underlying iterator is weighted.
    */
    typedef typename weighted_iterator_traits<Iter>::type type;
  };

  /**
     Specialization for StrideIterator using iterator_traits with base()
   */
  template <class Iter>
  struct iterator_traits<StrideIterator<Iter> > {
    /**
       data_reference same as for underlying iterator
     */
    typedef typename iterator_traits<Iter>::data_reference data_reference;

    /**
       weight_reference same as for underlying iterator
     */
    typedef typename iterator_traits<Iter>::weight_reference weight_reference;

    /**
       \return data of iterator
    */
    data_reference data(StrideIterator<Iter> iter) const 
    { return iterator_traits<Iter>().data(iter.base()); }

    /**
       \return weight of iterator
    */
    weight_reference weight(StrideIterator<Iter> iter) const 
    { return iterator_traits<Iter>().weight(iter.base()); }

  };

  /**
     @brief Adaptor using a stride on underlying iterator

     Works as underlying iterator except that all arithmetic uses the
     stride, so e.g., ++StrideIterator returns underlying
     _iterator+stride

  */
  template<typename Iter>
  class StrideIterator 
    : public boost::iterator_adaptor<StrideIterator<Iter>, Iter>
  {
    typedef boost::iterator_adaptor<StrideIterator<Iter>,Iter> super_t;

  public:
    /// type of underlying iterator
    typedef Iter iterator_type;

    /*
    /// value type
    typedef typename std::iterator_traits<Iter>::value_type value_type;
    /// difference type
    typedef typename std::iterator_traits<Iter>::difference_type difference_type;
    /// reference
    typedef typename std::iterator_traits<Iter>::reference reference;
    /// pointer
    typedef typename std::iterator_traits<Iter>::pointer pointer;
    /// weighted_iterator_tag if iterator is weighted
    typedef typename yat::utility::weighted_iterator_traits<Iter>::type w_type;
    */

    /**
       \brief default constructor

       Using default constructor of BASE iterator.
     */
    explicit StrideIterator(size_t stride=1)
      : StrideIterator::iterator_adaptor_(), stride_(stride) {}

    /**
       \brief Constructor
    */
    explicit StrideIterator(Iter p, size_t stride=1)
      : StrideIterator::iterator_adaptor_(p), stride_(stride) {}

    
    /**
       \brief Copy constructor
     */
    StrideIterator(const StrideIterator& other)
      : StrideIterator::iterator_adaptor_(other.base()), stride_(other.stride()) 
    {}

    /**
       \brief Conversion constructor. 

       Create a StrideIterator<Iter> from a StrideIterator<I2>. Possible
       if I2 is convertible to a Iter. Constructor allows implicit
       conversions such as iterator to const_iterator.
     */
    template<typename I2>
    StrideIterator(StrideIterator<I2> other,
                   typename boost::enable_if_convertible<I2, Iter>::type* = 0 )
      : StrideIterator::iterator_adaptor_(other.base()), 
        stride_(other.stride()) {}

    /** 
        \brief Assignment operator
     */
    StrideIterator& operator=(const StrideIterator& rhs)
    {
      stride_ = rhs.stride();
      this->base_reference() = rhs.base();
      return *this;
    }

    /**
       \return stride
     */
    inline size_t stride(void) const { return stride_; }

  private:
    // to give base class access to private parts
    friend class boost::iterator_core_access;
    
    size_t stride_;

    //typedef typename StrideIterator::iterator_adaptor_::difference_type
    typedef typename StrideIterator::iterator_adaptor_::difference_type
    difference_t;

    void advance(typename super_t::difference_type n)
    { this->base_reference() += stride_*n; }

    void decrement(void) { this->base_reference()-=stride_; }

    template <class OtherIterator>
    typename super_t::difference_type 
    distance_to(const StrideIterator<OtherIterator>& other) const
    { 
      // casting to int to avoid loss of sign in numerator
      return (other.base() - this->base() )/static_cast<int>(stride_); 
    }

    void increment(void) { this->base_reference()+=stride_; }

  };





}}} // of namespace utility, yat, and theplu

#endif