liuxiaolong
2021-07-20 58d904a328c0d849769b483e901a0be9426b8209
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/*=============================================================================
    Copyright (c) 2001-2011 Joel de Guzman
    Copyright (c) 2005-2006 Dan Marsden
    Copyright (c) 2018 Kohei Takahashi
 
    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)
==============================================================================*/
#if !defined(BOOST_FUSION_VALUE_AT_IMPL_20061101_0745)
#define BOOST_FUSION_VALUE_AT_IMPL_20061101_0745
 
#include <boost/fusion/support/config.hpp>
#include <boost/fusion/sequence/intrinsic/value_at.hpp>
#include <boost/utility/result_of.hpp>
 
namespace boost { namespace fusion {
    struct transform_view_tag;
    struct transform_view2_tag;
 
    namespace extension
    {
        template<typename Tag>
        struct value_at_impl;
 
        template<>
        struct value_at_impl<transform_view_tag>
        {
            template<typename Seq, typename N>
            struct apply
            {
                typedef typename Seq::transform_type F;
                typedef typename result_of::value_at<typename Seq::sequence_type, N>::type value_type;
                typedef typename boost::result_of<F(value_type)>::type type;
            };
        };
 
        template<>
        struct value_at_impl<transform_view2_tag>
        {
            template<typename Seq, typename N>
            struct apply
            {
                typedef typename Seq::transform_type F;
                typedef typename result_of::value_at<typename Seq::sequence1_type, N>::type value1_type;
                typedef typename result_of::value_at<typename Seq::sequence2_type, N>::type value2_type;
                typedef typename boost::result_of<F(value1_type, value2_type)>::type type;
            };
        };
    }
}}
 
#endif