forked from boostorg/fusion
118 lines
3.7 KiB
C++
118 lines
3.7 KiB
C++
/*=============================================================================
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Copyright (c) 2001-2006 Joel de Guzman
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Copyright (c) 2005-2006 Dan Marsden
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Distributed under 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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==============================================================================*/
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#if !defined(BOOST_FUSION_VARIANT_ITERATOR_12112006_1617)
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#define BOOST_FUSION_VARIANT_ITERATOR_12112006_1617
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#include <boost/fusion/iterator/iterator_facade.hpp>
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#include <boost/mpl/next.hpp>
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#include <boost/mpl/int.hpp>
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#include <boost/mpl/distance.hpp>
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#include <boost/mpl/deref.hpp>
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#include <boost/mpl/eval_if.hpp>
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#include <boost/type_traits/is_const.hpp>
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#include <boost/type_traits/add_const.hpp>
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#include <boost/type_traits/add_reference.hpp>
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#include <boost/variant/get.hpp>
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#include <boost/detail/workaround.hpp>
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namespace boost { namespace fusion
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{
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struct forward_traversal_tag;
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template<typename Variant, typename MPLIterator>
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struct variant_iterator
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: iterator_facade<variant_iterator<Variant, MPLIterator>, forward_traversal_tag>
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{
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typedef Variant variant_type;
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typedef MPLIterator iterator;
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variant_iterator(Variant& var)
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: var_(var) {}
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Variant& var_;
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template<typename Iterator>
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struct next
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{
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typedef variant_iterator<
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typename Iterator::variant_type,
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typename mpl::next<typename Iterator::iterator>::type> type;
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static type
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call(Iterator const& i)
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{
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return type(i.var_);
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}
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};
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template<typename I1, typename I2>
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struct distance
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: mpl::distance<
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typename I1::iterator,
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typename I2::iterator>
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{
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typedef typename mpl::distance<
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typename I1::iterator,
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typename I2::iterator>::type type;
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static type call(I1 const& i1, I2 const& i2)
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{
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return type();
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}
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};
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template<typename Iterator>
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struct value_of
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: mpl::deref<typename Iterator::iterator>
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{};
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template <typename Iterator>
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struct deref
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{
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typedef typename
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mpl::eval_if<
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is_const<typename Iterator::variant_type>
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, add_const<typename mpl::deref<typename Iterator::iterator>::type>
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, mpl::deref<typename Iterator::iterator>
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>::type
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value_type;
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typedef typename
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add_reference<value_type>::type
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type;
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#if BOOST_WORKAROUND(BOOST_MSVC, < 1400)
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// for some unknown reason (compiler bug) VC7.1 gets confused with
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// variant and optional get functions.
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static type
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call(Iterator const & it)
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{
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boost::detail::variant::get_visitor<type> v;
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typedef typename mpl::deref<typename Iterator::iterator>::type type;
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if (type* result = it.var_.apply_visitor(v))
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return *result;
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it.var_ = type(); // prime the variant
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return *it.var_.apply_visitor(v); // no-throw!
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}
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#else
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static type
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call(Iterator const & it)
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{
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typedef typename mpl::deref<typename Iterator::iterator>::type type;
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if (type* result = boost::get<type>(&it.var_))
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return *result;
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it.var_ = type(); // prime the variant
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return *boost::get<type>(&it.var_); // no-throw!
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}
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#endif
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};
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};
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}}
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#endif
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