250 lines
6.2 KiB
Plaintext
250 lines
6.2 KiB
Plaintext
/* Copyright 2003-2015 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See 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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*
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* See http://www.boost.org/libs/multi_index for library home page.
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*/
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#ifndef BOOST_MULTI_INDEX_DETAIL_INDEX_MATCHER_HPP
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#define BOOST_MULTI_INDEX_DETAIL_INDEX_MATCHER_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
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#include <algorithm>
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#include <boost/noncopyable.hpp>
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#include <boost/multi_index/detail/auto_space.hpp>
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#include <boost/multi_index/detail/raw_ptr.hpp>
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#include <cstddef>
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#include <functional>
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namespace boost{
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namespace multi_index{
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namespace detail{
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/* index_matcher compares a sequence of elements against a
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* base sequence, identifying those elements that belong to the
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* longest subsequence which is ordered with respect to the base.
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* For instance, if the base sequence is:
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*
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* 0 1 2 3 4 5 6 7 8 9
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*
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* and the compared sequence (not necesarilly the same length):
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*
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* 1 4 2 3 0 7 8 9
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*
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* the elements of the longest ordered subsequence are:
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*
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* 1 2 3 7 8 9
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*
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* The algorithm for obtaining such a subsequence is called
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* Patience Sorting, described in ch. 1 of:
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* Aldous, D., Diaconis, P.: "Longest increasing subsequences: from
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* patience sorting to the Baik-Deift-Johansson Theorem", Bulletin
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* of the American Mathematical Society, vol. 36, no 4, pp. 413-432,
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* July 1999.
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* http://www.ams.org/bull/1999-36-04/S0273-0979-99-00796-X/
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* S0273-0979-99-00796-X.pdf
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*
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* This implementation is not fully generic since it assumes that
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* the sequences given are pointed to by index iterators (having a
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* get_node() memfun.)
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*/
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namespace index_matcher{
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/* The algorithm stores the nodes of the base sequence and a number
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* of "piles" that are dynamically updated during the calculation
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* stage. From a logical point of view, nodes form an independent
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* sequence from piles. They are stored together so as to minimize
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* allocated memory.
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*/
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struct entry
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{
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entry(void* node_,std::size_t pos_=0):node(node_),pos(pos_){}
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/* node stuff */
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void* node;
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std::size_t pos;
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entry* previous;
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bool ordered;
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struct less_by_node
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{
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bool operator()(
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const entry& x,const entry& y)const
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{
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return std::less<void*>()(x.node,y.node);
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}
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};
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/* pile stuff */
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std::size_t pile_top;
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entry* pile_top_entry;
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struct less_by_pile_top
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{
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bool operator()(
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const entry& x,const entry& y)const
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{
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return x.pile_top<y.pile_top;
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}
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};
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};
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/* common code operating on void *'s */
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template<typename Allocator>
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class algorithm_base:private noncopyable
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{
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protected:
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algorithm_base(const Allocator& al,std::size_t size):
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spc(al,size),size_(size),n_(0),sorted(false)
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{
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}
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void add(void* node)
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{
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entries()[n_]=entry(node,n_);
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++n_;
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}
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void begin_algorithm()const
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{
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if(!sorted){
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std::sort(entries(),entries()+size_,entry::less_by_node());
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sorted=true;
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}
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num_piles=0;
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}
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void add_node_to_algorithm(void* node)const
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{
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entry* ent=
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std::lower_bound(
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entries(),entries()+size_,
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entry(node),entry::less_by_node()); /* localize entry */
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ent->ordered=false;
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std::size_t n=ent->pos; /* get its position */
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entry dummy(0);
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dummy.pile_top=n;
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entry* pile_ent= /* find the first available pile */
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std::lower_bound( /* to stack the entry */
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entries(),entries()+num_piles,
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dummy,entry::less_by_pile_top());
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pile_ent->pile_top=n; /* stack the entry */
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pile_ent->pile_top_entry=ent;
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/* if not the first pile, link entry to top of the preceding pile */
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if(pile_ent>&entries()[0]){
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ent->previous=(pile_ent-1)->pile_top_entry;
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}
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if(pile_ent==&entries()[num_piles]){ /* new pile? */
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++num_piles;
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}
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}
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void finish_algorithm()const
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{
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if(num_piles>0){
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/* Mark those elements which are in their correct position, i.e. those
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* belonging to the longest increasing subsequence. These are those
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* elements linked from the top of the last pile.
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*/
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entry* ent=entries()[num_piles-1].pile_top_entry;
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for(std::size_t n=num_piles;n--;){
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ent->ordered=true;
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ent=ent->previous;
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}
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}
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}
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bool is_ordered(void * node)const
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{
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return std::lower_bound(
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entries(),entries()+size_,
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entry(node),entry::less_by_node())->ordered;
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}
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private:
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entry* entries()const{return raw_ptr<entry*>(spc.data());}
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auto_space<entry,Allocator> spc;
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std::size_t size_;
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std::size_t n_;
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mutable bool sorted;
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mutable std::size_t num_piles;
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};
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/* The algorithm has three phases:
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* - Initialization, during which the nodes of the base sequence are added.
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* - Execution.
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* - Results querying, through the is_ordered memfun.
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*/
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template<typename Node,typename Allocator>
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class algorithm:private algorithm_base<Allocator>
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{
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typedef algorithm_base<Allocator> super;
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public:
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algorithm(const Allocator& al,std::size_t size):super(al,size){}
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void add(Node* node)
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{
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super::add(node);
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}
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template<typename IndexIterator>
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void execute(IndexIterator first,IndexIterator last)const
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{
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super::begin_algorithm();
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for(IndexIterator it=first;it!=last;++it){
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add_node_to_algorithm(get_node(it));
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}
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super::finish_algorithm();
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}
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bool is_ordered(Node* node)const
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{
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return super::is_ordered(node);
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}
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private:
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void add_node_to_algorithm(Node* node)const
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{
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super::add_node_to_algorithm(node);
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}
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template<typename IndexIterator>
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static Node* get_node(IndexIterator it)
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{
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return static_cast<Node*>(it.get_node());
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}
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};
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} /* namespace multi_index::detail::index_matcher */
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} /* namespace multi_index::detail */
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} /* namespace multi_index */
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} /* namespace boost */
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#endif
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