Initial Commit
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Jordan Sherer
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// Copyright David Abrahams 2003. Use, modification and distribution is
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// subject to the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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#ifndef FACADE_ITERATOR_CATEGORY_DWA20031118_HPP
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# define FACADE_ITERATOR_CATEGORY_DWA20031118_HPP
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# include <boost/iterator/iterator_categories.hpp>
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# include <boost/mpl/or.hpp> // used in iterator_tag inheritance logic
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# include <boost/mpl/and.hpp>
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# include <boost/mpl/if.hpp>
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# include <boost/mpl/eval_if.hpp>
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# include <boost/mpl/identity.hpp>
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# include <boost/mpl/assert.hpp>
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# include <boost/type_traits/is_same.hpp>
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# include <boost/type_traits/is_const.hpp>
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# include <boost/type_traits/is_reference.hpp>
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# include <boost/type_traits/is_convertible.hpp>
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# include <boost/type_traits/is_same.hpp>
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# include <boost/iterator/detail/config_def.hpp> // try to keep this last
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# ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY
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# include <boost/detail/indirect_traits.hpp>
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# endif
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//
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// iterator_category deduction for iterator_facade
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//
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namespace boost {
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namespace iterators {
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// forward declaration
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struct use_default;
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namespace detail {
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struct input_output_iterator_tag
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: std::input_iterator_tag
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{
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// Using inheritance for only input_iterator_tag helps to avoid
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// ambiguities when a stdlib implementation dispatches on a
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// function which is overloaded on both input_iterator_tag and
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// output_iterator_tag, as STLPort does, in its __valid_range
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// function. I claim it's better to avoid the ambiguity in these
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// cases.
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operator std::output_iterator_tag() const
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{
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return std::output_iterator_tag();
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}
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};
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//
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// True iff the user has explicitly disabled writability of this
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// iterator. Pass the iterator_facade's Value parameter and its
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// nested ::reference type.
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//
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template <class ValueParam, class Reference>
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struct iterator_writability_disabled
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# ifdef BOOST_ITERATOR_REF_CONSTNESS_KILLS_WRITABILITY // Adding Thomas' logic?
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: mpl::or_<
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is_const<Reference>
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, boost::detail::indirect_traits::is_reference_to_const<Reference>
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, is_const<ValueParam>
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>
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# else
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: is_const<ValueParam>
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# endif
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{};
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//
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// Convert an iterator_facade's traversal category, Value parameter,
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// and ::reference type to an appropriate old-style category.
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//
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// Due to changeset 21683, this now never results in a category convertible
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// to output_iterator_tag.
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//
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// Change at: https://svn.boost.org/trac/boost/changeset/21683
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template <class Traversal, class ValueParam, class Reference>
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struct iterator_facade_default_category
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: mpl::eval_if<
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mpl::and_<
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is_reference<Reference>
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, is_convertible<Traversal,forward_traversal_tag>
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>
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, mpl::eval_if<
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is_convertible<Traversal,random_access_traversal_tag>
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, mpl::identity<std::random_access_iterator_tag>
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, mpl::if_<
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is_convertible<Traversal,bidirectional_traversal_tag>
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, std::bidirectional_iterator_tag
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, std::forward_iterator_tag
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>
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>
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, typename mpl::eval_if<
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mpl::and_<
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is_convertible<Traversal, single_pass_traversal_tag>
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// check for readability
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, is_convertible<Reference, ValueParam>
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>
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, mpl::identity<std::input_iterator_tag>
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, mpl::identity<Traversal>
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>
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>
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{
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};
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// True iff T is convertible to an old-style iterator category.
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template <class T>
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struct is_iterator_category
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: mpl::or_<
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is_convertible<T,std::input_iterator_tag>
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, is_convertible<T,std::output_iterator_tag>
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>
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{
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};
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template <class T>
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struct is_iterator_traversal
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: is_convertible<T,incrementable_traversal_tag>
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{};
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//
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// A composite iterator_category tag convertible to Category (a pure
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// old-style category) and Traversal (a pure traversal tag).
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// Traversal must be a strict increase of the traversal power given by
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// Category.
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//
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template <class Category, class Traversal>
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struct iterator_category_with_traversal
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: Category, Traversal
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{
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// Make sure this isn't used to build any categories where
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// convertibility to Traversal is redundant. Should just use the
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// Category element in that case.
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BOOST_MPL_ASSERT_NOT((
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is_convertible<
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typename iterator_category_to_traversal<Category>::type
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, Traversal
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>));
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BOOST_MPL_ASSERT((is_iterator_category<Category>));
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BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>));
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BOOST_MPL_ASSERT_NOT((is_iterator_traversal<Category>));
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# if !BOOST_WORKAROUND(BOOST_MSVC, BOOST_TESTED_AT(1310))
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BOOST_MPL_ASSERT((is_iterator_traversal<Traversal>));
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# endif
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};
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// Computes an iterator_category tag whose traversal is Traversal and
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// which is appropriate for an iterator
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template <class Traversal, class ValueParam, class Reference>
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struct facade_iterator_category_impl
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{
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BOOST_MPL_ASSERT_NOT((is_iterator_category<Traversal>));
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typedef typename iterator_facade_default_category<
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Traversal,ValueParam,Reference
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>::type category;
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typedef typename mpl::if_<
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is_same<
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Traversal
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, typename iterator_category_to_traversal<category>::type
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>
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, category
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, iterator_category_with_traversal<category,Traversal>
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>::type type;
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};
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//
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// Compute an iterator_category for iterator_facade
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//
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template <class CategoryOrTraversal, class ValueParam, class Reference>
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struct facade_iterator_category
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: mpl::eval_if<
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is_iterator_category<CategoryOrTraversal>
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, mpl::identity<CategoryOrTraversal> // old-style categories are fine as-is
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, facade_iterator_category_impl<CategoryOrTraversal,ValueParam,Reference>
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>
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{
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};
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}}} // namespace boost::iterators::detail
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# include <boost/iterator/detail/config_undef.hpp>
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#endif // FACADE_ITERATOR_CATEGORY_DWA20031118_HPP
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