// In header: <boost/range/any_range.hpp>

template<typename Value, typename Reference = const Value, 
         typename Difference = std::ptrdiff_t> 
struct lazy_range : public boost::any_range< Value, bidirectional_traversal_tag, Reference, Difference >
{
  // construct/copy/destruct
  template<typename T> lazy_range(const T &);
};