williamr@2: // (C) Copyright David Abrahams 2002.
williamr@2: // (C) Copyright Jeremy Siek    2002.
williamr@2: // (C) Copyright Thomas Witt    2002.
williamr@2: // Distributed under the Boost Software License, Version 1.0. (See
williamr@2: // accompanying file LICENSE_1_0.txt or copy at
williamr@2: // http://www.boost.org/LICENSE_1_0.txt)
williamr@2: #ifndef BOOST_ITERATOR_ADAPTOR_23022003THW_HPP
williamr@2: #define BOOST_ITERATOR_ADAPTOR_23022003THW_HPP
williamr@2: 
williamr@2: #include <boost/static_assert.hpp>
williamr@2: #include <boost/iterator.hpp>
williamr@2: #include <boost/detail/iterator.hpp>
williamr@2: 
williamr@2: #include <boost/iterator/iterator_categories.hpp>
williamr@2: #include <boost/iterator/iterator_facade.hpp>
williamr@2: #include <boost/iterator/detail/enable_if.hpp>
williamr@2: 
williamr@2: #include <boost/mpl/and.hpp>
williamr@2: #include <boost/mpl/not.hpp>
williamr@2: #include <boost/mpl/or.hpp>
williamr@2: 
williamr@2: #include <boost/type_traits/is_same.hpp>
williamr@2: #include <boost/type_traits/is_convertible.hpp>
williamr@2: 
williamr@2: #ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
williamr@2: # include <boost/type_traits/remove_reference.hpp>
williamr@2: #else 
williamr@2: # include <boost/type_traits/add_reference.hpp>
williamr@2: #endif 
williamr@2: 
williamr@2: #include <boost/iterator/detail/config_def.hpp>
williamr@2: 
williamr@2: #include <boost/iterator/iterator_traits.hpp>
williamr@2: 
williamr@2: namespace boost
williamr@2: {
williamr@2:   // Used as a default template argument internally, merely to
williamr@2:   // indicate "use the default", this can also be passed by users
williamr@2:   // explicitly in order to specify that the default should be used.
williamr@2:   struct use_default;
williamr@2:   
williamr@2: # ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
williamr@2:   // the incompleteness of use_default causes massive problems for
williamr@2:   // is_convertible (naturally).  This workaround is fortunately not
williamr@2:   // needed for vc6/vc7.
williamr@2:   template<class To>
williamr@2:   struct is_convertible<use_default,To>
williamr@2:     : mpl::false_ {};
williamr@2: # endif 
williamr@2:   
williamr@2:   namespace detail
williamr@2:   {
williamr@2: 
williamr@2:     // 
williamr@2:     // Result type used in enable_if_convertible meta function.
williamr@2:     // This can be an incomplete type, as only pointers to 
williamr@2:     // enable_if_convertible< ... >::type are used.
williamr@2:     // We could have used void for this, but conversion to
williamr@2:     // void* is just to easy.
williamr@2:     //
williamr@2:     struct enable_type;
williamr@2:   }
williamr@2: 
williamr@2: 
williamr@2:   //
williamr@2:   // enable_if for use in adapted iterators constructors.
williamr@2:   //
williamr@2:   // In order to provide interoperability between adapted constant and
williamr@2:   // mutable iterators, adapted iterators will usually provide templated
williamr@2:   // conversion constructors of the following form
williamr@2:   //
williamr@2:   // template <class BaseIterator>
williamr@2:   // class adapted_iterator :
williamr@2:   //   public iterator_adaptor< adapted_iterator<Iterator>, Iterator >
williamr@2:   // {
williamr@2:   // public:
williamr@2:   //   
williamr@2:   //   ...
williamr@2:   //
williamr@2:   //   template <class OtherIterator>
williamr@2:   //   adapted_iterator(
williamr@2:   //       OtherIterator const& it
williamr@2:   //     , typename enable_if_convertible<OtherIterator, Iterator>::type* = 0);
williamr@2:   //
williamr@2:   //   ...
williamr@2:   // };
williamr@2:   //
williamr@2:   // enable_if_convertible is used to remove those overloads from the overload
williamr@2:   // set that cannot be instantiated. For all practical purposes only overloads
williamr@2:   // for constant/mutable interaction will remain. This has the advantage that
williamr@2:   // meta functions like boost::is_convertible do not return false positives,
williamr@2:   // as they can only look at the signature of the conversion constructor
williamr@2:   // and not at the actual instantiation.
williamr@2:   //
williamr@2:   // enable_if_interoperable can be safely used in user code. It falls back to
williamr@2:   // always enabled for compilers that don't support enable_if or is_convertible. 
williamr@2:   // There is no need for compiler specific workarounds in user code. 
williamr@2:   //
williamr@2:   // The operators implementation relies on boost::is_convertible not returning
williamr@2:   // false positives for user/library defined iterator types. See comments
williamr@2:   // on operator implementation for consequences.
williamr@2:   //
williamr@2: #  if BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
williamr@2:   
williamr@2:   template<typename From, typename To>
williamr@2:   struct enable_if_convertible
williamr@2:   {
williamr@2:      typedef typename mpl::if_<
williamr@2:          mpl::or_<
williamr@2:              is_same<From,To>
williamr@2:            , is_convertible<From, To>
williamr@2:          >
williamr@2:       , detail::enable_type
williamr@2:       , int&
williamr@2:      >::type type;
williamr@2:   };
williamr@2:   
williamr@2: #  elif defined(BOOST_NO_IS_CONVERTIBLE) || defined(BOOST_NO_SFINAE)
williamr@2:   
williamr@2:   template <class From, class To>
williamr@2:   struct enable_if_convertible
williamr@2:   {
williamr@2:       typedef detail::enable_type type;
williamr@2:   };
williamr@2:   
williamr@2: #  elif BOOST_WORKAROUND(_MSC_FULL_VER, BOOST_TESTED_AT(13102292)) && BOOST_MSVC > 1300
williamr@2:   
williamr@2:   // For some reason vc7.1 needs us to "cut off" instantiation
williamr@2:   // of is_convertible in a few cases.
williamr@2:   template<typename From, typename To>
williamr@2:   struct enable_if_convertible
williamr@2:     : iterators::enable_if<
williamr@2:         mpl::or_<
williamr@2:             is_same<From,To>
williamr@2:           , is_convertible<From, To>
williamr@2:         >
williamr@2:       , detail::enable_type
williamr@2:     >
williamr@2:   {};
williamr@2:   
williamr@2: #  else 
williamr@2:   
williamr@2:   template<typename From, typename To>
williamr@2:   struct enable_if_convertible
williamr@2:     : iterators::enable_if<
williamr@2:           is_convertible<From, To>
williamr@2:         , detail::enable_type
williamr@2:       >
williamr@2:   {};
williamr@2:       
williamr@2: # endif
williamr@2:   
williamr@2:   //
williamr@2:   // Default template argument handling for iterator_adaptor
williamr@2:   //
williamr@2:   namespace detail
williamr@2:   {
williamr@2:     // If T is use_default, return the result of invoking
williamr@2:     // DefaultNullaryFn, otherwise return T.
williamr@2:     template <class T, class DefaultNullaryFn>
williamr@2:     struct ia_dflt_help
williamr@2:       : mpl::eval_if<
williamr@2:             is_same<T, use_default>
williamr@2:           , DefaultNullaryFn
williamr@2:           , mpl::identity<T>
williamr@2:         >
williamr@2:     {
williamr@2:     };
williamr@2: 
williamr@2:     // A metafunction which computes an iterator_adaptor's base class,
williamr@2:     // a specialization of iterator_facade.
williamr@2:     template <
williamr@2:         class Derived
williamr@2:       , class Base
williamr@2:       , class Value
williamr@2:       , class Traversal
williamr@2:       , class Reference
williamr@2:       , class Difference
williamr@2:     >
williamr@2:     struct iterator_adaptor_base
williamr@2:     {
williamr@2:         typedef iterator_facade<
williamr@2:             Derived
williamr@2:             
williamr@2: # ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
williamr@2:           , typename detail::ia_dflt_help<
williamr@2:                 Value
williamr@2:               , mpl::eval_if<
williamr@2:                     is_same<Reference,use_default>
williamr@2:                   , iterator_value<Base>
williamr@2:                   , remove_reference<Reference>
williamr@2:                 >
williamr@2:             >::type
williamr@2: # else
williamr@2:           , typename detail::ia_dflt_help<
williamr@2:                 Value, iterator_value<Base>
williamr@2:             >::type
williamr@2: # endif
williamr@2:             
williamr@2:           , typename detail::ia_dflt_help<
williamr@2:                 Traversal
williamr@2:               , iterator_traversal<Base>
williamr@2:             >::type
williamr@2: 
williamr@2:           , typename detail::ia_dflt_help<
williamr@2:                 Reference
williamr@2:               , mpl::eval_if<
williamr@2:                     is_same<Value,use_default>
williamr@2:                   , iterator_reference<Base>
williamr@2:                   , add_reference<Value>
williamr@2:                 >
williamr@2:             >::type
williamr@2: 
williamr@2:           , typename detail::ia_dflt_help<
williamr@2:                 Difference, iterator_difference<Base>
williamr@2:             >::type
williamr@2:         >
williamr@2:         type;
williamr@2:     };
williamr@2:   
williamr@2:     // workaround for aC++ CR JAGaf33512
williamr@2:     template <class Tr1, class Tr2>
williamr@2:     inline void iterator_adaptor_assert_traversal ()
williamr@2:     {
williamr@2:       BOOST_STATIC_ASSERT((is_convertible<Tr1, Tr2>::value));
williamr@2:     }
williamr@2:   }
williamr@2:   
williamr@2:   //
williamr@2:   // Iterator Adaptor
williamr@2:   //
williamr@2:   // The parameter ordering changed slightly with respect to former
williamr@2:   // versions of iterator_adaptor The idea is that when the user needs
williamr@2:   // to fiddle with the reference type it is highly likely that the
williamr@2:   // iterator category has to be adjusted as well.  Any of the
williamr@2:   // following four template arguments may be ommitted or explicitly
williamr@2:   // replaced by use_default.
williamr@2:   //
williamr@2:   //   Value - if supplied, the value_type of the resulting iterator, unless
williamr@2:   //      const. If const, a conforming compiler strips constness for the
williamr@2:   //      value_type. If not supplied, iterator_traits<Base>::value_type is used
williamr@2:   //
williamr@2:   //   Category - the traversal category of the resulting iterator. If not
williamr@2:   //      supplied, iterator_traversal<Base>::type is used.
williamr@2:   //
williamr@2:   //   Reference - the reference type of the resulting iterator, and in
williamr@2:   //      particular, the result type of operator*(). If not supplied but
williamr@2:   //      Value is supplied, Value& is used. Otherwise
williamr@2:   //      iterator_traits<Base>::reference is used.
williamr@2:   //
williamr@2:   //   Difference - the difference_type of the resulting iterator. If not
williamr@2:   //      supplied, iterator_traits<Base>::difference_type is used.
williamr@2:   //
williamr@2:   template <
williamr@2:       class Derived
williamr@2:     , class Base
williamr@2:     , class Value        = use_default
williamr@2:     , class Traversal    = use_default
williamr@2:     , class Reference    = use_default
williamr@2:     , class Difference   = use_default
williamr@2:   >
williamr@2:   class iterator_adaptor
williamr@2:     : public detail::iterator_adaptor_base<
williamr@2:         Derived, Base, Value, Traversal, Reference, Difference
williamr@2:       >::type
williamr@2:   {
williamr@2:       friend class iterator_core_access;
williamr@2: 
williamr@2:    protected:
williamr@2:       typedef typename detail::iterator_adaptor_base<
williamr@2:           Derived, Base, Value, Traversal, Reference, Difference
williamr@2:       >::type super_t;
williamr@2:    public:
williamr@2:       iterator_adaptor() {}
williamr@2: 
williamr@2:       explicit iterator_adaptor(Base const &iter)
williamr@2:           : m_iterator(iter)
williamr@2:       {
williamr@2:       }
williamr@2: 
williamr@2:       typedef Base base_type;
williamr@2: 
williamr@2:       Base const& base() const
williamr@2:         { return m_iterator; }
williamr@2: 
williamr@2:    protected:
williamr@2:       // for convenience in derived classes
williamr@2:       typedef iterator_adaptor<Derived,Base,Value,Traversal,Reference,Difference> iterator_adaptor_;
williamr@2:       
williamr@2:       //
williamr@2:       // lvalue access to the Base object for Derived
williamr@2:       //
williamr@2:       Base const& base_reference() const
williamr@2:         { return m_iterator; }
williamr@2: 
williamr@2:       Base& base_reference()
williamr@2:         { return m_iterator; }
williamr@2: 
williamr@2:    private:
williamr@2:       //
williamr@2:       // Core iterator interface for iterator_facade.  This is private
williamr@2:       // to prevent temptation for Derived classes to use it, which
williamr@2:       // will often result in an error.  Derived classes should use
williamr@2:       // base_reference(), above, to get direct access to m_iterator.
williamr@2:       // 
williamr@2:       typename super_t::reference dereference() const
williamr@2:         { return *m_iterator; }
williamr@2: 
williamr@2:       template <
williamr@2:       class OtherDerived, class OtherIterator, class V, class C, class R, class D
williamr@2:       >   
williamr@2:       bool equal(iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& x) const
williamr@2:       {
williamr@2:         // Maybe readd with same_distance
williamr@2:         //           BOOST_STATIC_ASSERT(
williamr@2:         //               (detail::same_category_and_difference<Derived,OtherDerived>::value)
williamr@2:         //               );
williamr@2:           return m_iterator == x.base();
williamr@2:       }
williamr@2: 
williamr@2:       typedef typename iterator_category_to_traversal<
williamr@2:           typename super_t::iterator_category
williamr@2:       >::type my_traversal;
williamr@2: 
williamr@2: # define BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(cat) \
williamr@2:       detail::iterator_adaptor_assert_traversal<my_traversal, cat>();
williamr@2: 
williamr@2:       void advance(typename super_t::difference_type n)
williamr@2:       {
williamr@2:           BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag)
williamr@2:           m_iterator += n;
williamr@2:       }
williamr@2:   
williamr@2:       void increment() { ++m_iterator; }
williamr@2: 
williamr@2:       void decrement() 
williamr@2:       {
williamr@2:           BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(bidirectional_traversal_tag)
williamr@2:            --m_iterator;
williamr@2:       }
williamr@2: 
williamr@2:       template <
williamr@2:           class OtherDerived, class OtherIterator, class V, class C, class R, class D
williamr@2:       >   
williamr@2:       typename super_t::difference_type distance_to(
williamr@2:           iterator_adaptor<OtherDerived, OtherIterator, V, C, R, D> const& y) const
williamr@2:       {
williamr@2:           BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL(random_access_traversal_tag)
williamr@2:           // Maybe readd with same_distance
williamr@2:           //           BOOST_STATIC_ASSERT(
williamr@2:           //               (detail::same_category_and_difference<Derived,OtherDerived>::value)
williamr@2:           //               );
williamr@2:           return y.base() - m_iterator;
williamr@2:       }
williamr@2: 
williamr@2: # undef BOOST_ITERATOR_ADAPTOR_ASSERT_TRAVERSAL
williamr@2:       
williamr@2:    private: // data members
williamr@2:       Base m_iterator;
williamr@2:   };
williamr@2: 
williamr@2: } // namespace boost
williamr@2: 
williamr@2: #include <boost/iterator/detail/config_undef.hpp>
williamr@2: 
williamr@2: #endif // BOOST_ITERATOR_ADAPTOR_23022003THW_HPP