216 lines
6.3 KiB
Plaintext
216 lines
6.3 KiB
Plaintext
// (C) Copyright Jeremy Siek 2002.
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// Distributed under the Boost Software License, Version 1.0. (See
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// accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_ITERATOR_CATEGORIES_HPP
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# define BOOST_ITERATOR_CATEGORIES_HPP
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# include <boost/config.hpp>
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# include <boost/detail/iterator.hpp>
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# include <boost/iterator/detail/config_def.hpp>
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# include <boost/detail/workaround.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/placeholders.hpp>
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# include <boost/mpl/aux_/lambda_support.hpp>
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# include <boost/type_traits/is_convertible.hpp>
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# include <boost/static_assert.hpp>
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namespace boost {
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namespace iterators {
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//
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// Traversal Categories
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//
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struct no_traversal_tag {};
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struct incrementable_traversal_tag
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: no_traversal_tag
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{
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// incrementable_traversal_tag() {}
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// incrementable_traversal_tag(std::output_iterator_tag const&) {};
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};
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struct single_pass_traversal_tag
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: incrementable_traversal_tag
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{
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// single_pass_traversal_tag() {}
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// single_pass_traversal_tag(std::input_iterator_tag const&) {};
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};
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struct forward_traversal_tag
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: single_pass_traversal_tag
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{
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// forward_traversal_tag() {}
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// forward_traversal_tag(std::forward_iterator_tag const&) {};
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};
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struct bidirectional_traversal_tag
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: forward_traversal_tag
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{
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// bidirectional_traversal_tag() {};
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// bidirectional_traversal_tag(std::bidirectional_iterator_tag const&) {};
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};
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struct random_access_traversal_tag
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: bidirectional_traversal_tag
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{
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// random_access_traversal_tag() {};
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// random_access_traversal_tag(std::random_access_iterator_tag const&) {};
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};
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namespace detail
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{
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//
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// Convert a "strictly old-style" iterator category to a traversal
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// tag. This is broken out into a separate metafunction to reduce
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// the cost of instantiating iterator_category_to_traversal, below,
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// for new-style types.
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//
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template <class Cat>
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struct old_category_to_traversal
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: mpl::eval_if<
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is_convertible<Cat,std::random_access_iterator_tag>
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, mpl::identity<random_access_traversal_tag>
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, mpl::eval_if<
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is_convertible<Cat,std::bidirectional_iterator_tag>
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, mpl::identity<bidirectional_traversal_tag>
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, mpl::eval_if<
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is_convertible<Cat,std::forward_iterator_tag>
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, mpl::identity<forward_traversal_tag>
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, mpl::eval_if<
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is_convertible<Cat,std::input_iterator_tag>
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, mpl::identity<single_pass_traversal_tag>
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, mpl::eval_if<
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is_convertible<Cat,std::output_iterator_tag>
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, mpl::identity<incrementable_traversal_tag>
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, void
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>
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>
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>
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>
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>
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{};
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} // namespace detail
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//
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// Convert an iterator category into a traversal tag
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//
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template <class Cat>
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struct iterator_category_to_traversal
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: mpl::eval_if< // if already convertible to a traversal tag, we're done.
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is_convertible<Cat,incrementable_traversal_tag>
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, mpl::identity<Cat>
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, boost::iterators::detail::old_category_to_traversal<Cat>
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>
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{};
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// Trait to get an iterator's traversal category
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template <class Iterator = mpl::_1>
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struct iterator_traversal
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: iterator_category_to_traversal<
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typename boost::detail::iterator_traits<Iterator>::iterator_category
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>
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{};
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# ifdef BOOST_MPL_CFG_NO_FULL_LAMBDA_SUPPORT
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// Hack because BOOST_MPL_AUX_LAMBDA_SUPPORT doesn't seem to work
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// out well. Instantiating the nested apply template also
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// requires instantiating iterator_traits on the
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// placeholder. Instead we just specialize it as a metafunction
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// class.
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template <>
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struct iterator_traversal<mpl::_1>
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{
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template <class T>
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struct apply : iterator_traversal<T>
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{};
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};
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template <>
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struct iterator_traversal<mpl::_>
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: iterator_traversal<mpl::_1>
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{};
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# endif
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//
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// Convert an iterator traversal to one of the traversal tags.
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//
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template <class Traversal>
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struct pure_traversal_tag
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: mpl::eval_if<
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is_convertible<Traversal,random_access_traversal_tag>
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, mpl::identity<random_access_traversal_tag>
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, mpl::eval_if<
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is_convertible<Traversal,bidirectional_traversal_tag>
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, mpl::identity<bidirectional_traversal_tag>
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, mpl::eval_if<
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is_convertible<Traversal,forward_traversal_tag>
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, mpl::identity<forward_traversal_tag>
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, mpl::eval_if<
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is_convertible<Traversal,single_pass_traversal_tag>
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, mpl::identity<single_pass_traversal_tag>
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, mpl::eval_if<
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is_convertible<Traversal,incrementable_traversal_tag>
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, mpl::identity<incrementable_traversal_tag>
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, void
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>
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>
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>
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>
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>
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{
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};
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//
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// Trait to retrieve one of the iterator traversal tags from the iterator category or traversal.
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//
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template <class Iterator = mpl::_1>
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struct pure_iterator_traversal
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: pure_traversal_tag<typename iterator_traversal<Iterator>::type>
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{};
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# ifdef BOOST_MPL_CFG_NO_FULL_LAMBDA_SUPPORT
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template <>
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struct pure_iterator_traversal<mpl::_1>
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{
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template <class T>
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struct apply : pure_iterator_traversal<T>
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{};
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};
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template <>
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struct pure_iterator_traversal<mpl::_>
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: pure_iterator_traversal<mpl::_1>
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{};
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# endif
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} // namespace iterators
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using iterators::no_traversal_tag;
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using iterators::incrementable_traversal_tag;
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using iterators::single_pass_traversal_tag;
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using iterators::forward_traversal_tag;
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using iterators::bidirectional_traversal_tag;
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using iterators::random_access_traversal_tag;
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using iterators::iterator_category_to_traversal;
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using iterators::iterator_traversal;
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// This import is needed for backward compatibility with Boost.Range:
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// boost/range/detail/demote_iterator_traversal_tag.hpp
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// It should be removed when that header is fixed.
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namespace detail {
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using iterators::pure_traversal_tag;
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} // namespace detail
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} // namespace boost
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#include <boost/iterator/detail/config_undef.hpp>
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#endif // BOOST_ITERATOR_CATEGORIES_HPP
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