// 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