--- /dev/null
+// Copyright David Abrahams 2003. Use, modification and distribution is
+// subject to the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+#ifndef FACADE_ITERATOR_CATEGORY_DWA20031118_HPP
+# define FACADE_ITERATOR_CATEGORY_DWA20031118_HPP
+
+# include <boost/iterator/iterator_categories.hpp>
+
+# include <boost/mpl/or.hpp> // used in iterator_tag inheritance logic
+# include <boost/mpl/and.hpp>
+# include <boost/mpl/if.hpp>
+# include <boost/mpl/eval_if.hpp>
+# include <boost/mpl/identity.hpp>
+# include <boost/mpl/assert.hpp>
+
+# include <boost/type_traits/is_same.hpp>
+# include <boost/type_traits/is_const.hpp>
+# include <boost/type_traits/is_reference.hpp>
+# include <boost/type_traits/is_convertible.hpp>
+
+# include <boost/type_traits/is_same.hpp>
+
+# include <boost/iterator/detail/config_def.hpp> // try to keep this last
+
+# ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
+# include <boost/detail/indirect_traits.hpp>
+# endif
+
+//
+// iterator_category deduction for iterator_facade
+//
+
+// forward declaration
+namespace boost { struct use_default; }
+
+namespace boost { namespace detail {
+
+struct input_output_iterator_tag
+ : std::input_iterator_tag
+{
+ // Using inheritance for only input_iterator_tag helps to avoid
+ // ambiguities when a stdlib implementation dispatches on a
+ // function which is overloaded on both input_iterator_tag and
+ // output_iterator_tag, as STLPort does, in its __valid_range
+ // function. I claim it's better to avoid the ambiguity in these
+ // cases.
+ operator std::output_iterator_tag() const
+ {
+ return std::output_iterator_tag();
+ }
+};
+
+//
+// True iff the user has explicitly disabled writability of this
+// iterator. Pass the iterator_facade's Value parameter and its
+// nested ::reference type.
+//
+template <class ValueParam, class Reference>
+struct iterator_writability_disabled
+# ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY // Adding Thomas' logic?
+ : mpl::or_<
+ is_const<Reference>
+ , boost::detail::indirect_traits::is_reference_to_const<Reference>
+ , is_const<ValueParam>
+ >
+# else
+ : is_const<ValueParam>
+# endif
+{};
+
+
+//
+// Convert an iterator_facade's traversal category, Value parameter,
+// and ::reference type to an appropriate old-style category.
+//
+// If writability has been disabled per the above metafunction, the
+// result will not be convertible to output_iterator_tag.
+//
+// Otherwise, if Traversal == single_pass_traversal_tag, the following
+// conditions will result in a tag that is convertible both to
+// input_iterator_tag and output_iterator_tag:
+//
+// 1. Reference is a reference to non-const
+// 2. Reference is not a reference and is convertible to Value
+//
+template <class Traversal, class ValueParam, class Reference>
+struct iterator_facade_default_category
+ : mpl::eval_if<
+ mpl::and_<
+ is_reference<Reference>
+ , is_convertible<Traversal,forward_traversal_tag>
+ >
+ , mpl::eval_if<
+ is_convertible<Traversal,random_access_traversal_tag>
+ , mpl::identity<std::random_access_iterator_tag>
+ , mpl::if_<
+ is_convertible<Traversal,bidirectional_traversal_tag>
+ , std::bidirectional_iterator_tag
+ , std::forward_iterator_tag
+ >
+ >
+ , typename mpl::eval_if<
+ mpl::and_<
+ is_convertible<Traversal, single_pass_traversal_tag>
+
+ // check for readability
+ , is_convertible<Reference, ValueParam>
+ >
+ , mpl::identity<std::input_iterator_tag>
+ , mpl::identity<Traversal>
+ >
+ >
+{
+};
+
+// True iff T is convertible to an old-style iterator category.
+template <class T>
+struct is_iterator_category
+ : mpl::or_<
+ is_convertible<T,std::input_iterator_tag>
+ , is_convertible<T,std::output_iterator_tag>
+ >
+{
+};
+
+template <class T>
+struct is_iterator_traversal
+ : is_convertible<T,incrementable_traversal_tag>
+{};
+
+//
+// A composite iterator_category tag convertible to Category (a pure
+// old-style category) and Traversal (a pure traversal tag).
+// Traversal must be a strict increase of the traversal power given by
+// Category.
+//
+template <class Category, class Traversal>
+struct iterator_category_with_traversal
+ : Category, Traversal
+{
+# if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
+ // Make sure this isn't used to build any categories where
+ // convertibility to Traversal is redundant. Should just use the
+ // Category element in that case.
+ BOOST_MPL_ASSERT_NOT((
+ is_convertible<
+ typename iterator_category_to_traversal<Category>::type
+ , Traversal
+ >));
+
+ BOOST_MPL_ASSERT((is_iterator_category<Category>));
+ BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>));
+ BOOST_MPL_ASSERT_NOT((is_iterator_traversal<Category>));
+# if !BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1310))
+ BOOST_MPL_ASSERT((is_iterator_traversal<Traversal>));
+# endif
+# endif
+};
+
+// Computes an iterator_category tag whose traversal is Traversal and
+// which is appropriate for an iterator
+template <class Traversal, class ValueParam, class Reference>
+struct facade_iterator_category_impl
+{
+# if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300)
+ BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>));
+# endif
+
+ typedef typename iterator_facade_default_category<
+ Traversal,ValueParam,Reference
+ >::type category;
+
+ typedef typename mpl::if_<
+ is_same<
+ Traversal
+ , typename iterator_category_to_traversal<category>::type
+ >
+ , category
+ , iterator_category_with_traversal<category,Traversal>
+ >::type type;
+};
+
+//
+// Compute an iterator_category for iterator_facade
+//
+template <class CategoryOrTraversal, class ValueParam, class Reference>
+struct facade_iterator_category
+ : mpl::eval_if<
+ is_iterator_category<CategoryOrTraversal>
+ , mpl::identity<CategoryOrTraversal> // old-style categories are fine as-is
+ , facade_iterator_category_impl<CategoryOrTraversal,ValueParam,Reference>
+ >
+{
+};
+
+}} // namespace boost::detail
+
+# include <boost/iterator/detail/config_undef.hpp>
+
+#endif // FACADE_ITERATOR_CATEGORY_DWA20031118_HPP
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