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#ifndef COMPARE_ELEMENT_INDEXES_H
#define COMPARE_ELEMENT_INDEXES_H

#include <functional>

#include "AbstractLinAlgPack_Types.hpp"

namespace AbstractLinAlgPack {

/** @name Comparision function objects for sparse element objects.
  *
  * These function objects are used to compare element indexes so the
  * templated objects must support the index() operation.
  */
//@{

/// ele1.index() < ele2.index() 
template<class T_Element>
struct compare_element_indexes_less
  : public std::unary_function< T_Element, typename T_Element::index_type >
{
  bool operator()(const T_Element& ele1, const T_Element& ele2) {
    return ele1.index() < ele2.index();
  }
  bool operator()(typename T_Element::index_type i, const T_Element& ele2) {
    return i < ele2.index();
  }
  bool operator()(const T_Element& ele1, typename T_Element::index_type i) {
    return ele1.index() < i;
  }
};

/// ele.index() == i
template<class T_Element>
struct compare_element_indexes_equal_to
  : public std::unary_function< T_Element, typename T_Element::index_type >
{
  compare_element_indexes_equal_to( typename T_Element::index_type i )
    : i_(i)
  {}
  bool operator()(const T_Element& ele) {
    return ele.index() == i_;
  }
private:
  typename T_Element::index_type i_;
  // Not defined and not to be called
  compare_element_indexes_equal_to();
};

//@}

}	// end namespace AbstractLinAlgPack

#endif   // COMPARE_ELEMENT_INDEXES_H
