Chris@16: 
Chris@16: #ifndef BOOST_MPL_MAP_AUX_AT_IMPL_HPP_INCLUDED
Chris@16: #define BOOST_MPL_MAP_AUX_AT_IMPL_HPP_INCLUDED
Chris@16: 
Chris@16: // Copyright Aleksey Gurtovoy 2003-2004
Chris@16: // Copyright David Abrahams 2003-2004
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. 
Chris@16: // (See accompanying file LICENSE_1_0.txt or copy at 
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: // See http://www.boost.org/libs/mpl for documentation.
Chris@16: 
Chris@101: // $Id$
Chris@101: // $Date$
Chris@101: // $Revision$
Chris@16: 
Chris@16: #include <boost/mpl/at_fwd.hpp>
Chris@16: #include <boost/mpl/long.hpp>
Chris@16: #include <boost/mpl/map/aux_/tag.hpp>
Chris@16: #include <boost/mpl/aux_/order_impl.hpp>
Chris@16: #include <boost/mpl/aux_/overload_names.hpp>
Chris@16: #include <boost/mpl/aux_/type_wrapper.hpp>
Chris@16: #include <boost/mpl/aux_/ptr_to_ref.hpp>
Chris@16: #include <boost/mpl/aux_/static_cast.hpp>
Chris@16: #include <boost/mpl/aux_/config/typeof.hpp>
Chris@16: #include <boost/mpl/aux_/config/ctps.hpp>
Chris@16: 
Chris@16: #if !defined(BOOST_MPL_CFG_TYPEOF_BASED_SEQUENCES)
Chris@16: #   include <boost/mpl/eval_if.hpp>
Chris@16: #   include <boost/mpl/pair.hpp>
Chris@16: #   include <boost/mpl/void.hpp>
Chris@16: #   include <boost/mpl/aux_/config/static_constant.hpp>
Chris@16: #endif
Chris@16: 
Chris@16: namespace boost { namespace mpl {
Chris@16: 
Chris@16: #if defined(BOOST_MPL_CFG_TYPEOF_BASED_SEQUENCES)
Chris@16: 
Chris@16: template< typename Map, typename Key >
Chris@16: struct m_at
Chris@16: {
Chris@16:     typedef aux::type_wrapper<Key> key_;
Chris@16:     typedef __typeof__( BOOST_MPL_AUX_OVERLOAD_CALL_VALUE_BY_KEY(
Chris@16:           Map
Chris@16:         , BOOST_MPL_AUX_STATIC_CAST(key_*, 0)
Chris@16:         ) ) type;
Chris@16: };
Chris@16: 
Chris@16: template<>
Chris@16: struct at_impl< aux::map_tag >
Chris@16: {
Chris@16:     template< typename Map, typename Key > struct apply
Chris@16:         : aux::wrapped_type< typename m_at<
Chris@16:               Map
Chris@16:             , Key
Chris@16:             >::type >
Chris@16:     {
Chris@16:     };
Chris@16: };
Chris@16: 
Chris@16: // agurt 31/jan/04: two-step implementation for the sake of GCC 3.x
Chris@16: template< typename Map, long order > 
Chris@16: struct item_by_order_impl
Chris@16: {
Chris@16:     typedef __typeof__( BOOST_MPL_AUX_OVERLOAD_CALL_ITEM_BY_ORDER(
Chris@16:           Map 
Chris@16:         , BOOST_MPL_AUX_STATIC_CAST(long_<order>*, 0)
Chris@16:         ) ) type;
Chris@16: };
Chris@16: 
Chris@16: template< typename Map, long order >
Chris@16: struct item_by_order
Chris@16:     : aux::wrapped_type<
Chris@16:           typename item_by_order_impl<Map,order>::type
Chris@16:         >
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: #else // BOOST_MPL_CFG_TYPEOF_BASED_SEQUENCES
Chris@16: 
Chris@16: #   if !defined(BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION)
Chris@16: 
Chris@16: template< typename Map, long n > struct m_at
Chris@16: {
Chris@16:     typedef void_ type;
Chris@16: };
Chris@16: 
Chris@16: #   else
Chris@16: 
Chris@16: template< long n > struct m_at_impl
Chris@16: {
Chris@16:     template< typename Map > struct result_
Chris@16:     {
Chris@16:         typedef void_ type;
Chris@16:     };
Chris@16: };
Chris@16: 
Chris@16: template< typename Map, long n > struct m_at
Chris@16: {
Chris@16:     typedef typename m_at_impl<n>::result_<Map>::type type;
Chris@16: };
Chris@16: 
Chris@16: #   endif
Chris@16: 
Chris@16: 
Chris@16: template<>
Chris@16: struct at_impl< aux::map_tag >
Chris@16: {
Chris@16:     template< typename Map, typename Key > struct apply
Chris@16:     {
Chris@16:         typedef typename m_at< Map, (x_order_impl<Map,Key>::value - 2) >::type item_;       
Chris@16:         typedef typename eval_if<
Chris@16:               is_void_<item_>
Chris@16:             , void_
Chris@16:             , second<item_>
Chris@16:             >::type type;
Chris@16:     };
Chris@16: };
Chris@16: 
Chris@16: template< typename Map, long order > struct is_item_masked
Chris@16: {
Chris@16:     BOOST_STATIC_CONSTANT(bool, value = 
Chris@16:           sizeof( BOOST_MPL_AUX_OVERLOAD_CALL_IS_MASKED(
Chris@16:               Map
Chris@16:             , BOOST_MPL_AUX_STATIC_CAST(long_<order>*, 0)
Chris@16:             ) ) == sizeof(aux::yes_tag)
Chris@16:         );
Chris@16: };
Chris@16: 
Chris@16: template< typename Map, long order > struct item_by_order
Chris@16: {    
Chris@16:     typedef typename eval_if_c< 
Chris@16:           is_item_masked<Map,order>::value
Chris@16:         , void_
Chris@16:         , m_at<Map,(order - 2)>
Chris@16:         >::type type;
Chris@16: };
Chris@16: 
Chris@16: #endif
Chris@16: 
Chris@16: }}
Chris@16: 
Chris@16: #endif // BOOST_MPL_SET_AUX_AT_IMPL_HPP_INCLUDED