mirror of
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574 lines
16 KiB
C++
574 lines
16 KiB
C++
// Copyright David Abrahams and Thomas Becker 2000-2006. Distributed
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// under the Boost Software License, Version 1.0. (See accompanying
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// 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_ZIP_ITERATOR_TMB_07_13_2003_HPP_
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# define BOOST_ZIP_ITERATOR_TMB_07_13_2003_HPP_
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#include <stddef.h>
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#include <boost/iterator.hpp>
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#include <boost/iterator/iterator_traits.hpp>
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#include <boost/iterator/iterator_facade.hpp>
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#include <boost/iterator/iterator_adaptor.hpp> // for enable_if_convertible
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#include <boost/iterator/iterator_categories.hpp>
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#include <boost/detail/iterator.hpp>
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#include <boost/iterator/minimum_category.hpp>
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#include <boost/tuple/tuple.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/mpl/and.hpp>
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#include <boost/mpl/apply.hpp>
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#include <boost/mpl/eval_if.hpp>
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#include <boost/mpl/lambda.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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namespace boost {
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namespace iterators {
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// Zip iterator forward declaration for zip_iterator_base
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template<typename IteratorTuple>
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class zip_iterator;
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// One important design goal of the zip_iterator is to isolate all
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// functionality whose implementation relies on the current tuple
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// implementation. This goal has been achieved as follows: Inside
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// the namespace detail there is a namespace tuple_impl_specific.
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// This namespace encapsulates all functionality that is specific
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// to the current Boost tuple implementation. More precisely, the
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// namespace tuple_impl_specific provides the following tuple
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// algorithms and meta-algorithms for the current Boost tuple
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// implementation:
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//
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// tuple_meta_transform
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// tuple_meta_accumulate
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// tuple_transform
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// tuple_for_each
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//
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// If the tuple implementation changes, all that needs to be
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// replaced is the implementation of these four (meta-)algorithms.
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namespace detail
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{
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// Functors to be used with tuple algorithms
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//
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template<typename DiffType>
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class advance_iterator
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{
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public:
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advance_iterator(DiffType step) : m_step(step) {}
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template<typename Iterator>
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void operator()(Iterator& it) const
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{ it += m_step; }
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private:
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DiffType m_step;
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};
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//
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struct increment_iterator
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{
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template<typename Iterator>
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void operator()(Iterator& it)
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{ ++it; }
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};
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//
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struct decrement_iterator
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{
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template<typename Iterator>
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void operator()(Iterator& it)
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{ --it; }
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};
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//
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struct dereference_iterator
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{
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template<typename Iterator>
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struct apply
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{
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typedef typename
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boost::detail::iterator_traits<Iterator>::reference
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type;
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};
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template<typename Iterator>
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typename apply<Iterator>::type operator()(Iterator const& it)
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{ return *it; }
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};
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// The namespace tuple_impl_specific provides two meta-
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// algorithms and two algorithms for tuples.
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//
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namespace tuple_impl_specific
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{
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// Meta-transform algorithm for tuples
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//
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template<typename Tuple, class UnaryMetaFun>
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struct tuple_meta_transform;
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template<typename Tuple, class UnaryMetaFun>
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struct tuple_meta_transform_impl
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{
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typedef tuples::cons<
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typename mpl::apply1<
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typename mpl::lambda<UnaryMetaFun>::type
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, typename Tuple::head_type
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>::type
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, typename tuple_meta_transform<
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typename Tuple::tail_type
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, UnaryMetaFun
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>::type
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> type;
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};
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template<typename Tuple, class UnaryMetaFun>
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struct tuple_meta_transform
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: mpl::eval_if<
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boost::is_same<Tuple, tuples::null_type>
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, mpl::identity<tuples::null_type>
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, tuple_meta_transform_impl<Tuple, UnaryMetaFun>
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>
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{
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};
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// Meta-accumulate algorithm for tuples. Note: The template
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// parameter StartType corresponds to the initial value in
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// ordinary accumulation.
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//
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template<class Tuple, class BinaryMetaFun, class StartType>
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struct tuple_meta_accumulate;
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template<
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typename Tuple
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, class BinaryMetaFun
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, typename StartType
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>
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struct tuple_meta_accumulate_impl
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{
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typedef typename mpl::apply2<
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typename mpl::lambda<BinaryMetaFun>::type
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, typename Tuple::head_type
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, typename tuple_meta_accumulate<
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typename Tuple::tail_type
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, BinaryMetaFun
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, StartType
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>::type
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>::type type;
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};
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template<
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typename Tuple
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, class BinaryMetaFun
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, typename StartType
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>
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struct tuple_meta_accumulate
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: mpl::eval_if<
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boost::is_same<Tuple, tuples::null_type>
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, mpl::identity<StartType>
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, tuple_meta_accumulate_impl<
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Tuple
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, BinaryMetaFun
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, StartType
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>
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>
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{
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};
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#if defined(BOOST_NO_FUNCTION_TEMPLATE_ORDERING) \
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|| ( \
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BOOST_WORKAROUND(BOOST_INTEL_CXX_VERSION, != 0) && defined(_MSC_VER) \
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)
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// Not sure why intel's partial ordering fails in this case, but I'm
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// assuming int's an MSVC bug-compatibility feature.
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# define BOOST_TUPLE_ALGO_DISPATCH
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# define BOOST_TUPLE_ALGO(algo) algo##_impl
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# define BOOST_TUPLE_ALGO_TERMINATOR , int
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# define BOOST_TUPLE_ALGO_RECURSE , ...
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#else
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# define BOOST_TUPLE_ALGO(algo) algo
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# define BOOST_TUPLE_ALGO_TERMINATOR
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# define BOOST_TUPLE_ALGO_RECURSE
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#endif
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// transform algorithm for tuples. The template parameter Fun
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// must be a unary functor which is also a unary metafunction
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// class that computes its return type based on its argument
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// type. For example:
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//
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// struct to_ptr
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// {
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// template <class Arg>
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// struct apply
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// {
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// typedef Arg* type;
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// }
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//
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// template <class Arg>
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// Arg* operator()(Arg x);
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// };
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template<typename Fun>
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inline tuples::null_type BOOST_TUPLE_ALGO(tuple_transform)
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(tuples::null_type const&, Fun BOOST_TUPLE_ALGO_TERMINATOR)
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{ return tuples::null_type(); }
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template<typename Tuple, typename Fun>
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inline typename tuple_meta_transform<
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Tuple
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, Fun
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>::type
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BOOST_TUPLE_ALGO(tuple_transform)(
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const Tuple& t,
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Fun f
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BOOST_TUPLE_ALGO_RECURSE
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)
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{
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typedef typename tuple_meta_transform<
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BOOST_DEDUCED_TYPENAME Tuple::tail_type
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, Fun
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>::type transformed_tail_type;
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return tuples::cons<
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BOOST_DEDUCED_TYPENAME mpl::apply1<
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Fun, BOOST_DEDUCED_TYPENAME Tuple::head_type
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>::type
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, transformed_tail_type
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>(
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f(boost::tuples::get<0>(t)), tuple_transform(t.get_tail(), f)
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);
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}
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#ifdef BOOST_TUPLE_ALGO_DISPATCH
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template<typename Tuple, typename Fun>
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inline typename tuple_meta_transform<
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Tuple
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, Fun
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>::type
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tuple_transform(
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const Tuple& t,
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Fun f
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)
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{
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return tuple_transform_impl(t, f, 1);
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}
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#endif
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// for_each algorithm for tuples.
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//
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template<typename Fun>
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inline Fun BOOST_TUPLE_ALGO(tuple_for_each)(
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tuples::null_type
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, Fun f BOOST_TUPLE_ALGO_TERMINATOR
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)
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{ return f; }
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template<typename Tuple, typename Fun>
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inline Fun BOOST_TUPLE_ALGO(tuple_for_each)(
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Tuple& t
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, Fun f BOOST_TUPLE_ALGO_RECURSE)
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{
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f( t.get_head() );
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return tuple_for_each(t.get_tail(), f);
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}
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#ifdef BOOST_TUPLE_ALGO_DISPATCH
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template<typename Tuple, typename Fun>
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inline Fun
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tuple_for_each(
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Tuple& t,
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Fun f
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)
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{
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return tuple_for_each_impl(t, f, 1);
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}
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#endif
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// Equality of tuples. NOTE: "==" for tuples currently (7/2003)
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// has problems under some compilers, so I just do my own.
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// No point in bringing in a bunch of #ifdefs here. This is
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// going to go away with the next tuple implementation anyway.
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//
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inline bool tuple_equal(tuples::null_type, tuples::null_type)
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{ return true; }
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template<typename Tuple1, typename Tuple2>
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inline bool tuple_equal(Tuple1 const& t1, Tuple2 const& t2)
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{
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return t1.get_head() == t2.get_head() &&
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tuple_equal(t1.get_tail(), t2.get_tail());
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}
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}
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//
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// end namespace tuple_impl_specific
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template<typename Iterator>
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struct iterator_reference
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{
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typedef typename boost::detail::iterator_traits<Iterator>::reference type;
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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_reference<mpl::_1>
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{
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template <class T>
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struct apply : iterator_reference<T> {};
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};
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#endif
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// Metafunction to obtain the type of the tuple whose element types
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// are the reference types of an iterator tuple.
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//
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template<typename IteratorTuple>
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struct tuple_of_references
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: tuple_impl_specific::tuple_meta_transform<
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IteratorTuple,
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iterator_reference<mpl::_1>
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>
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{
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};
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// Metafunction to obtain the minimal traversal tag in a tuple
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// of iterators.
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//
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template<typename IteratorTuple>
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struct minimum_traversal_category_in_iterator_tuple
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{
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typedef typename tuple_impl_specific::tuple_meta_transform<
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IteratorTuple
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, pure_traversal_tag<iterator_traversal<> >
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>::type tuple_of_traversal_tags;
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typedef typename tuple_impl_specific::tuple_meta_accumulate<
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tuple_of_traversal_tags
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, minimum_category<>
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, random_access_traversal_tag
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>::type type;
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};
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// We need to call tuple_meta_accumulate with mpl::and_ as the
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// accumulating functor. To this end, we need to wrap it into
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// a struct that has exactly two arguments (that is, template
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// parameters) and not five, like mpl::and_ does.
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//
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template<typename Arg1, typename Arg2>
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struct and_with_two_args
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: mpl::and_<Arg1, Arg2>
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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. In this case I think it's an MPL bug
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template<>
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struct and_with_two_args<mpl::_1,mpl::_2>
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{
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template <class A1, class A2>
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struct apply : mpl::and_<A1,A2>
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{};
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};
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# endif
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///////////////////////////////////////////////////////////////////
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//
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// Class zip_iterator_base
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//
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// Builds and exposes the iterator facade type from which the zip
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// iterator will be derived.
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//
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template<typename IteratorTuple>
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struct zip_iterator_base
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{
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private:
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// Reference type is the type of the tuple obtained from the
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// iterators' reference types.
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typedef typename
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detail::tuple_of_references<IteratorTuple>::type reference;
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// Value type is the same as reference type.
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typedef reference value_type;
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// Difference type is the first iterator's difference type
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typedef typename boost::detail::iterator_traits<
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typename tuples::element<0, IteratorTuple>::type
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>::difference_type difference_type;
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// Traversal catetgory is the minimum traversal category in the
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// iterator tuple.
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typedef typename
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detail::minimum_traversal_category_in_iterator_tuple<
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IteratorTuple
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>::type traversal_category;
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public:
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// The iterator facade type from which the zip iterator will
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// be derived.
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typedef iterator_facade<
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zip_iterator<IteratorTuple>,
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value_type,
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traversal_category,
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reference,
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difference_type
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> type;
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};
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template <>
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struct zip_iterator_base<int>
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{
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typedef int type;
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};
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}
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/////////////////////////////////////////////////////////////////////
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//
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// zip_iterator class definition
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//
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template<typename IteratorTuple>
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class zip_iterator :
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public detail::zip_iterator_base<IteratorTuple>::type
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{
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// Typedef super_t as our base class.
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typedef typename
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detail::zip_iterator_base<IteratorTuple>::type super_t;
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// iterator_core_access is the iterator's best friend.
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friend class iterator_core_access;
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public:
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// Construction
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// ============
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// Default constructor
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zip_iterator() { }
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// Constructor from iterator tuple
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zip_iterator(IteratorTuple iterator_tuple)
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: m_iterator_tuple(iterator_tuple)
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{ }
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// Copy constructor
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template<typename OtherIteratorTuple>
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zip_iterator(
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const zip_iterator<OtherIteratorTuple>& other,
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typename enable_if_convertible<
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OtherIteratorTuple,
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IteratorTuple
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>::type* = 0
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) : m_iterator_tuple(other.get_iterator_tuple())
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{}
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// Get method for the iterator tuple.
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const IteratorTuple& get_iterator_tuple() const
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{ return m_iterator_tuple; }
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private:
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// Implementation of Iterator Operations
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// =====================================
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// Dereferencing returns a tuple built from the dereferenced
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// iterators in the iterator tuple.
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typename super_t::reference dereference() const
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{
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return detail::tuple_impl_specific::tuple_transform(
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get_iterator_tuple(),
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detail::dereference_iterator()
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);
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}
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// Two zip iterators are equal if all iterators in the iterator
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// tuple are equal. NOTE: It should be possible to implement this
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// as
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//
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// return get_iterator_tuple() == other.get_iterator_tuple();
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//
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// but equality of tuples currently (7/2003) does not compile
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// under several compilers. No point in bringing in a bunch
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// of #ifdefs here.
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//
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template<typename OtherIteratorTuple>
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bool equal(const zip_iterator<OtherIteratorTuple>& other) const
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{
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return detail::tuple_impl_specific::tuple_equal(
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get_iterator_tuple(),
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other.get_iterator_tuple()
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);
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}
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// Advancing a zip iterator means to advance all iterators in the
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// iterator tuple.
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void advance(typename super_t::difference_type n)
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{
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detail::tuple_impl_specific::tuple_for_each(
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m_iterator_tuple,
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detail::advance_iterator<BOOST_DEDUCED_TYPENAME super_t::difference_type>(n)
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);
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}
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// Incrementing a zip iterator means to increment all iterators in
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// the iterator tuple.
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void increment()
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{
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detail::tuple_impl_specific::tuple_for_each(
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m_iterator_tuple,
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detail::increment_iterator()
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);
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}
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// Decrementing a zip iterator means to decrement all iterators in
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// the iterator tuple.
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void decrement()
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{
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detail::tuple_impl_specific::tuple_for_each(
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m_iterator_tuple,
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detail::decrement_iterator()
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);
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}
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// Distance is calculated using the first iterator in the tuple.
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template<typename OtherIteratorTuple>
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typename super_t::difference_type distance_to(
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const zip_iterator<OtherIteratorTuple>& other
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) const
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{
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return boost::tuples::get<0>(other.get_iterator_tuple()) -
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boost::tuples::get<0>(this->get_iterator_tuple());
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}
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// Data Members
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// ============
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// The iterator tuple.
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IteratorTuple m_iterator_tuple;
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};
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// Make function for zip iterator
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//
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template<typename IteratorTuple>
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inline zip_iterator<IteratorTuple>
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make_zip_iterator(IteratorTuple t)
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{ return zip_iterator<IteratorTuple>(t); }
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} // namespace iterators
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using iterators::zip_iterator;
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using iterators::make_zip_iterator;
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} // namespace boost
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#endif
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