iterator_facade.hpp

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      , iterator_facade<Derived2, V2, TC2, R2, D2> const& rhs)
# else 
#  define BOOST_ITERATOR_FACADE_INTEROP_HEAD(prefix, op, result_type)   \
    template <                                                          \
        class Derived1, class V1, class TC1, class R1, class D1         \
      , class Derived2, class V2, class TC2, class R2, class D2         \
    >                                                                   \
    prefix typename detail::enable_if_interoperable<                    \
        Derived1, Derived2                                              \
      , typename mpl::apply2<result_type,Derived1,Derived2>::type       \
    >::type                                                             \
    operator op(                                                        \
        iterator_facade<Derived1, V1, TC1, R1, D1> const& lhs           \
      , iterator_facade<Derived2, V2, TC2, R2, D2> const& rhs)
# endif 

#  define BOOST_ITERATOR_FACADE_PLUS_HEAD(prefix,args)              \
    template <class Derived, class V, class TC, class R, class D>   \
    prefix Derived operator+ args

  //
  // Helper class for granting access to the iterator core interface.
  //
  // The simple core interface is used by iterator_facade. The core
  // interface of a user/library defined iterator type should not be made public
  // so that it does not clutter the public interface. Instead iterator_core_access
  // should be made friend so that iterator_facade can access the core
  // interface through iterator_core_access.
  //
  class iterator_core_access
  {
# if defined(BOOST_NO_MEMBER_TEMPLATE_FRIENDS)                  \
    || BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x551))
      // Tasteless as this may seem, making all members public allows member templates
      // to work in the absence of member template friends.
   public:
# else
      
      template <class I, class V, class TC, class R, class D> friend class iterator_facade;

#  define BOOST_ITERATOR_FACADE_RELATION(op)                                \
      BOOST_ITERATOR_FACADE_INTEROP_HEAD(friend,op, detail::always_bool2);

      BOOST_ITERATOR_FACADE_RELATION(==)
      BOOST_ITERATOR_FACADE_RELATION(!=)

      BOOST_ITERATOR_FACADE_RELATION(<)
      BOOST_ITERATOR_FACADE_RELATION(>)
      BOOST_ITERATOR_FACADE_RELATION(<=)
      BOOST_ITERATOR_FACADE_RELATION(>=)
#  undef BOOST_ITERATOR_FACADE_RELATION

      BOOST_ITERATOR_FACADE_INTEROP_HEAD(
          friend, -, detail::choose_difference_type)
      ;

      BOOST_ITERATOR_FACADE_PLUS_HEAD(
          friend                                
          , (iterator_facade<Derived, V, TC, R, D> const&
           , typename Derived::difference_type)
      )
      ;

      BOOST_ITERATOR_FACADE_PLUS_HEAD(
          friend
        , (typename Derived::difference_type
           , iterator_facade<Derived, V, TC, R, D> const&)
      )
      ;

# endif

      template <class Facade>
      static typename Facade::reference dereference(Facade const& f)
      {
          return f.dereference();
      }

      template <class Facade>
      static void increment(Facade& f)
      {
          f.increment();
      }

      template <class Facade>
      static void decrement(Facade& f)
      {
          f.decrement();
      }

      template <class Facade1, class Facade2>
      static bool equal(Facade1 const& f1, Facade2 const& f2, mpl::true_)
      {
          return f1.equal(f2);
      }

      template <class Facade1, class Facade2>
      static bool equal(Facade1 const& f1, Facade2 const& f2, mpl::false_)
      {
          return f2.equal(f1);
      }

      template <class Facade>
      static void advance(Facade& f, typename Facade::difference_type n)
      {
          f.advance(n);
      }

      template <class Facade1, class Facade2>
      static typename Facade1::difference_type distance_from(
          Facade1 const& f1, Facade2 const& f2, mpl::true_)
      {
          return -f1.distance_to(f2);
      }

      template <class Facade1, class Facade2>
      static typename Facade2::difference_type distance_from(
          Facade1 const& f1, Facade2 const& f2, mpl::false_)
      {
          return f2.distance_to(f1);
      }

      //
      // Curiously Recurring Template interface.
      //
      template <class I, class V, class TC, class R, class D>
      static I& derived(iterator_facade<I,V,TC,R,D>& facade)
      {
          return *static_cast<I*>(&facade);
      }

      template <class I, class V, class TC, class R, class D>
      static I const& derived(iterator_facade<I,V,TC,R,D> const& facade)
      {
          return *static_cast<I const*>(&facade);
      }

   private:
      // objects of this class are useless
      iterator_core_access(); //undefined
  };

  //
  // iterator_facade - use as a public base class for defining new
  // standard-conforming iterators.
  //
  template <
      class Derived             // The derived iterator type being constructed
    , class Value
    , class CategoryOrTraversal
    , class Reference   = Value&
    , class Difference  = std::ptrdiff_t
  >
  class iterator_facade
# ifdef BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE
    : public detail::iterator_facade_types<
         Value, CategoryOrTraversal, Reference, Difference
      >::base
#  undef BOOST_ITERATOR_FACADE_NEEDS_ITERATOR_BASE
# endif
  {
   private:
      //
      // Curiously Recurring Template interface.
      //
      Derived& derived()
      {
          return *static_cast<Derived*>(this);
      }

      Derived const& derived() const
      {
          return *static_cast<Derived const*>(this);
      }

      typedef detail::iterator_facade_types<
         Value, CategoryOrTraversal, Reference, Difference
      > associated_types;

   protected:
      // For use by derived classes
      typedef iterator_facade<Derived,Value,Reference,Difference> iterator_facade_;
      
   public:

      typedef typename associated_types::value_type value_type;
      typedef Reference reference;
      typedef Difference difference_type;
      typedef typename associated_types::pointer pointer;
      typedef typename associated_types::iterator_category iterator_category;

      reference operator*() const
      {
          return iterator_core_access::dereference(this->derived());
      }

      typename detail::operator_arrow_result<
          value_type
        , reference
        , pointer
      >::type
      operator->() const
      {
          return detail::operator_arrow_result<
              value_type
            , reference
            , pointer
          >::make(*this->derived());
      }
        
      typename detail::operator_brackets_result<Derived,Value,reference>::type
      operator[](difference_type n) const
      {
          typedef detail::use_operator_brackets_proxy<Value,Reference> use_proxy;
          
          return detail::make_operator_brackets_result<Derived>(
              this->derived() + n
            , use_proxy()
          );
      }

      Derived& operator++()
      {
          iterator_core_access::increment(this->derived());
          return this->derived();
      }

# if BOOST_WORKAROUND(BOOST_MSVC, == 1200)
      typename detail::postfix_increment_result<Derived,Value,Reference,CategoryOrTraversal>::type
      operator++(int)
      {
          typename detail::postfix_increment_result<Derived,Value,Reference,CategoryOrTraversal>::type
          tmp(this->derived());
          ++*this;
          return tmp;
      }
# endif
      
      Derived& operator--()
      {
          iterator_core_access::decrement(this->derived());
          return this->derived();
      }

      Derived operator--(int)
      {
          Derived tmp(this->derived());
          --*this;
          return tmp;
      }

      Derived& operator+=(difference_type n)
      {
          iterator_core_access::advance(this->derived(), n);
          return this->derived();
      }

      Derived& operator-=(difference_type n)
      {
          iterator_core_access::advance(this->derived(), -n);
          return this->derived();
      }

      Derived operator-(difference_type x) const
      {
          Derived result(this->derived());
          return result -= x;
      }

# if BOOST_WORKAROUND(BOOST_MSVC, <= 1200)
      // There appears to be a bug which trashes the data of classes
      // derived from iterator_facade when they are assigned unless we
      // define this assignment operator.  This bug is only revealed
      // (so far) in STLPort debug mode, but it's clearly a codegen
      // problem so we apply the workaround for all MSVC6.
      iterator_facade& operator=(iterator_facade const&)
      {
          return *this;
      }
# endif
  };

# if !BOOST_WORKAROUND(BOOST_MSVC, == 1200)
  template <class I, class V, class TC, class R, class D>
  typename detail::postfix_increment_result<I,V,R,TC>::type
  operator++(
      iterator_facade<I,V,TC,R,D>& i
    , int
  )
  {
      typename detail::postfix_increment_result<I,V,R,TC>::type
          tmp(*static_cast<I*>(&i));
      
      ++i;
      
      return tmp;
  }
# endif 

  
  //
  // Comparison operator implementation. The library supplied operators
  // enables the user to provide fully interoperable constant/mutable
  // iterator types. I.e. the library provides all operators
  // for all mutable/constant iterator combinations.
  //
  // Note though that this kind of interoperability for constant/mutable
  // iterators is not required by the standard for container iterators.
  // All the standard asks for is a conversion mutable -> constant.
  // Most standard library implementations nowadays provide fully interoperable
  // iterator implementations, but there are still heavily used implementations
  // that do not provide them. (Actually it's even worse, they do not provide
  // them for only a few iterators.)
  //
  // ?? Maybe a BOOST_ITERATOR_NO_FULL_INTEROPERABILITY macro should
  //    enable the user to turn off mixed type operators
  //
  // The library takes care to provide only the right operator overloads.
  // I.e.
  //
  // bool operator==(Iterator,      Iterator);
  // bool operator==(ConstIterator, Iterator);
  // bool operator==(Iterator,      ConstIterator);
  // bool operator==(ConstIterator, ConstIterator);
  //
  //   ...
  //
  // In order to do so it uses c++ idioms that are not yet widely supported
  // by current compiler releases. The library is designed to degrade gracefully
  // in the face of compiler deficiencies. In general compiler
  // deficiencies result in less strict error checking and more obscure
  // error messages, functionality is not affected.
  //
  // For full operation compiler support for "Substitution Failure Is Not An Error"
  // (aka. enable_if) and boost::is_convertible is required.
  //
  // The following problems occur if support is lacking.
  //
  // Pseudo code
  //
  // ---------------
  // AdaptorA<Iterator1> a1;
  // AdaptorA<Iterator2> a2;
  //
  // // This will result in a no such overload error in full operation
  // // If enable_if or is_convertible is not supported
  // // The instantiation will fail with an error hopefully indicating that
  // // there is no operator== for Iterator1, Iterator2
  // // The same will happen if no enable_if is used to remove
  // // false overloads from the templated conversion constructor
  // // of AdaptorA.
  //
  // a1 == a2;
  // ----------------
  //
  // AdaptorA<Iterator> a;
  // AdaptorB<Iterator> b;
  //
  // // This will result in a no such overload error in full operation
  // // If enable_if is not supported the static assert used
  // // in the operator implementation will fail.
  // // This will accidently work if is_convertible is not supported.
  //
  // a == b;
  // ----------------
  //

# ifdef BOOST_NO_ONE_WAY_ITERATOR_INTEROP
#  define BOOST_ITERATOR_CONVERTIBLE(a,b) mpl::true_()
# else
#  define BOOST_ITERATOR_CONVERTIBLE(a,b) is_convertible<a,b>()
# endif

# define BOOST_ITERATOR_FACADE_INTEROP(op, result_type, return_prefix, base_op) \
  BOOST_ITERATOR_FACADE_INTEROP_HEAD(inline, op, result_type)                   \
  {                                                                             \
      /* For those compilers that do not support enable_if */                   \
      BOOST_STATIC_ASSERT((                                                     \
          is_interoperable< Derived1, Derived2 >::value                         \
      ));                                                                       \
      return_prefix iterator_core_access::base_op(                              \
          *static_cast<Derived1 const*>(&lhs)                                   \
        , *static_cast<Derived2 const*>(&rhs)                                   \
        , BOOST_ITERATOR_CONVERTIBLE(Derived2,Derived1)                         \
      );                                                                        \
  }

# define BOOST_ITERATOR_FACADE_RELATION(op, return_prefix, base_op) \
  BOOST_ITERATOR_FACADE_INTEROP(                                    \
      op                                                            \
    , detail::always_bool2                                          \
    , return_prefix                                                 \
    , base_op                                                       \
  )

  BOOST_ITERATOR_FACADE_RELATION(==, return, equal)
  BOOST_ITERATOR_FACADE_RELATION(!=, return !, equal)

  BOOST_ITERATOR_FACADE_RELATION(<, return 0 >, distance_from)
  BOOST_ITERATOR_FACADE_RELATION(>, return 0 <, distance_from)
  BOOST_ITERATOR_FACADE_RELATION(<=, return 0 >=, distance_from)
  BOOST_ITERATOR_FACADE_RELATION(>=, return 0 <=, distance_from)
# undef BOOST_ITERATOR_FACADE_RELATION

  // operator- requires an additional part in the static assertion
  BOOST_ITERATOR_FACADE_INTEROP(
      -
    , detail::choose_difference_type
    , return
    , distance_from
  )
# undef BOOST_ITERATOR_FACADE_INTEROP
# undef BOOST_ITERATOR_FACADE_INTEROP_HEAD

# define BOOST_ITERATOR_FACADE_PLUS(args)           \
  BOOST_ITERATOR_FACADE_PLUS_HEAD(inline, args)     \
  {                                                 \
      Derived tmp(static_cast<Derived const&>(i));  \
      return tmp += n;                              \
  }

BOOST_ITERATOR_FACADE_PLUS((
  iterator_facade<Derived, V, TC, R, D> const& i
  , typename Derived::difference_type n
))

BOOST_ITERATOR_FACADE_PLUS((
    typename Derived::difference_type n
    , iterator_facade<Derived, V, TC, R, D> const& i
))
# undef BOOST_ITERATOR_FACADE_PLUS
# undef BOOST_ITERATOR_FACADE_PLUS_HEAD

} // namespace boost

#include <boost/iterator/detail/config_undef.hpp>

#endif // BOOST_ITERATOR_FACADE_23022003THW_HPP