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// Copyright (C) 2005-2009 Daniel James
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_UNORDERED_DETAIL_EXTRACT_KEY_HPP_INCLUDED
#define BOOST_UNORDERED_DETAIL_EXTRACT_KEY_HPP_INCLUDED
#include <boost/config.hpp>
#include <boost/type_traits/remove_const.hpp>
#include <boost/unordered/detail/fwd.hpp>
namespace boost {
namespace unordered_detail {
// key extractors
//
// no throw
//
// 'extract_key' is called with the emplace parameters to return a
// key if available or 'no_key' is one isn't and will need to be
// constructed. This could be done by overloading the emplace implementation
// for the different cases, but that's a bit tricky on compilers without
// variadic templates.
struct no_key {
no_key() {}
template <class T> no_key(T const&) {}
};
template <class ValueType>
struct set_extractor
{
typedef ValueType value_type;
typedef ValueType key_type;
static key_type const& extract(key_type const& v)
{
return v;
}
static no_key extract()
{
return no_key();
}
#if defined(BOOST_UNORDERED_STD_FORWARD)
template <class... Args>
static no_key extract(Args const&...)
{
return no_key();
}
#else
template <class Arg>
static no_key extract(Arg const&)
{
return no_key();
}
template <class Arg>
static no_key extract(Arg const&, Arg const&)
{
return no_key();
}
#endif
static bool compare_mapped(value_type const&, value_type const&)
{
return true;
}
};
template <class Key, class ValueType>
struct map_extractor
{
typedef ValueType value_type;
typedef BOOST_DEDUCED_TYPENAME boost::remove_const<Key>::type key_type;
static key_type const& extract(value_type const& v)
{
return v.first;
}
static key_type const& extract(key_type const& v)
{
return v;
}
template <class Second>
static key_type const& extract(std::pair<key_type, Second> const& v)
{
return v.first;
}
template <class Second>
static key_type const& extract(
std::pair<key_type const, Second> const& v)
{
return v.first;
}
#if defined(BOOST_UNORDERED_STD_FORWARD)
template <class Arg1, class... Args>
static key_type const& extract(key_type const& k,
Arg1 const&, Args const&...)
{
return k;
}
template <class... Args>
static no_key extract(Args const&...)
{
return no_key();
}
#else
template <class Arg1>
static key_type const& extract(key_type const& k, Arg1 const&)
{
return k;
}
static no_key extract()
{
return no_key();
}
template <class Arg>
static no_key extract(Arg const&)
{
return no_key();
}
template <class Arg, class Arg1>
static no_key extract(Arg const&, Arg1 const&)
{
return no_key();
}
#endif
static bool compare_mapped(value_type const& x, value_type const& y)
{
return x.second == y.second;
}
};
}}
#endif
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Swift